Rolling Aluminum: From the Mine Through the Mill ACKNOWLEDGEMENTS This manual has been prepared with information and assistance from The Aluminum Association and member companies represented on the Sheet and Plate Division’s Technology Committee.

SHEET & PLATE DIVISION MEMBER COMPANIES Alcoa Inc. JW Aluminum Aleris Rolled Products Kaiser Aluminum and ALSCO Metals Corp. Chemical Corporation AMAG Rolling GmbH Koenig & Vits, Inc. ARCO Aluminum, Inc. Logan Aluminum, Inc. Golden Aluminm Nichols Aluminum Gulf Aluminium Rolling Novelis Inc. Mill Co. Rio Tinto Alcan Impol Aluminum Corp. United Aluminum Corporation Jupiter Aluminum Corporation Wise Metals Group

USE OF INFORMATION The use of any information contained herein by any member or non-member of The Aluminum Association is entirely voluntary. The Aluminum Association has used its best efforts in compiling the information contained in this book. While the Association believes that its compilation procedures are reliable, it does not warrant, either expressly or implied, the accuracy or completeness of this information. The Aluminum Association assumes no responsibility or liability for the use of the information herein.

All Aluminum Association published standards, data, specifications and other technical materials are reviewed and revised, reaffirmed or withdrawn on a periodic basis. Users are advised to contact The Aluminum Association to ascertain whether the information in this publication has been superseded in the interim between publication and proposed use.

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© Copyright 2008. Unauthorized reproduction by photocopy or any other method is illegal.

First Printing June 1990 Third Edition December 2007 Rolling Aluminum: From the Mine Through the Mill

HOW TO USE THIS PUBLICATION his publication enlarges upon the information presented in The Aluminum Association DVD “Rolling Aluminum: From the Mine Through the Mill”. TThe expanded explanations of various aspects of aluminum production and rolling appear where they are mentioned in the DVD. The user who wants to learn the general features of aluminum production and rolling will find them summarized in the DVD and the early paragraphs of each section of the manual and in its Self-Test Questions and Answers. For readers who want to understand these subjects more thoroughly, the full text of the manual provides more detailed explanations. The manual may also be used as a ready-reference, by consulting its subheaded Table of Contents and / or alphabetical index. Metric values of the US customary units in the manual have been included for the convenience of the reader and are not intended as precise arithmetic conversions. Where the products ( foil / sheet / plate) are defined by their thickness range, the actual metric gauge definition has also been included for reference. Finally, the loose-leaf format permits the easy insertion of product information, additional notes or future informational updates.

ABOUT THE ALUMINUM ASSOCIATION he Aluminum Association is an industry-wide trade organization representing US and foreign producers of aluminum, leading manufacturers of semi-fabricated aluminum Tproducts, secondary smelters and suppliers to the aluminum industry. The Association’s aims are to increase public and industrial understanding of alu - minum and the aluminum industry and — through its technical, statistical, marketing and information activities — to serve industries, consumers, financial analysts, educa - tors, government agencies and the public generally. For the aluminum industry and those industries that use aluminum, The Association helps develop standards and designation systems, helps prepare codes and specifica - tions involving aluminum products and studies technical problems of the industry. The Association maintains and periodically issues industry-wide statistics and records which are used as an authoritative source. Association members also join together on a number of commodity and end-market committees to conduct industry-wide market development programs.

Rolling Aluminum: From the Mine through the Mill CONTENTS Section-Page

INTRODUCTION Advantages of Aluminum ...... 1-1 1 Flat-Rolled Aluminum ...... 1-2 Aluminum Sheet Applications ...... 1-2 Aluminum Plate Applications ...... 1-2 Aluminum Foil Applications ...... 1-2 Specialty Products ...... 1-2 Definitions: Plate, Sheet, Foil ...... 1-4 Rolling Aluminum: General Description ...... 1-4 Technological Advances ...... 1-5 Self-Test Questions ...... 1-7

PRODUCTION OF ALUMINUM AND ITS ALLOYS Bauxite Mining ...... 2-1 2 Alumina Refining ...... 2-1 Aluminum Reduction: The Hall-Heroult Process ...... 2-2 Alloying ...... 2-5 Aluminum Alloy Series ...... 2-5 Heat-Treatable Alloys ...... 2-6 Non- Heat-Treatable Alloys ...... 2-6 Recycled Aluminum Scrap ...... 2-7 Addition of Alloying Elements ...... 2-7 Self-Test Questions ...... 2-9

PREPARATION OF ALUMINUM ALLOYS FOR ROLLING Metal Cleaning: Fluxing and Filtration ...... 3-1 3 Fluxing ...... 3-1 Alloy Sample Analysis ...... 3-1 Filtration ...... 3-2 Additives ...... 3-3 Continuous Casting of Sheet or Plate ...... 3-3 DC Ingot Casting ...... 3-6 Electromagnetic Casting (EMC ) ...... 3-7 Scalping ...... 3-7 Pre-Heating ...... 3-8 Purposes of Pre-Heating ...... 3-8 Pre-Heating Methods ...... 3-8 Self-Test Questions ...... 3-9 CONTENTS 6

THE ALUMINUM ROLLING MILL Description and Features ...... 4-1 4 Single-Stand and Tandem Mills ...... 4-3 Mill Rolls ...... 4-3 Roll Configurations ...... 4-4 Hot or Cold Rolling ...... 4-6 Hot Rolling : Metallurgical Effects ...... 4-7 Cold Rolling: Metallurgical Effects ...... 4-7 Self-Test Questions ...... 4-9

SHEET ROLLING OPERATIONS Breakdown Mill Parameters ...... 5-1 5 Breakdown Coolant /Lubricant Applications ...... 5-2 Breakdown Rolling ...... 5-3 Intermediate Hot Rolling ...... 5-3 Sheet Hot Rolling : The Tandem Mill ...... 5-4 Coiling and Edge Trimming ...... 5-5 Annealing ...... 5-6 Purposes of Annealing ...... 5-6 Full Annealing ...... 5-6 Partial Annealing ...... 5-7 Stabilization Annealing ...... 5-7 Annealing Methods ...... 5-7 Batch Annealing /Treatment ...... 5-7 Sheet Annealing /Treatment ...... 5-7 Cold Rolling ...... 5-8 Gauge and Profile Control ...... 5-8 Texturing and Embossing ...... 5-10 Self-Test Questions ...... 5-11

SHEET FINISHING Solution Heat Treating ...... 6-1 6 Metallurgical Function of Solution Heat Treating ...... 6-1 Solution Heat Treatment : “Soaking” ...... 6-2 Quenching ...... 6-2 Natural Aging (Precipitation Hardening ) ...... 6-3 Artificial Aging (Precipitation Heat Treatment) ...... 6-3 Slitting ...... 6-4 Tension- Leveling ...... 6-4 Surface Finishes ...... 6-4 Oiling ...... 6-5 Degreasing ...... 6-5 Coatings and Markings ...... 6-5 Cutting to Length ...... 6-5 Stretcher- Leveling ...... 6-6 Packaging and Storage ...... 6-6 Self-Test Questions ...... 6-7 CONTENTS 7

PLATE ROLLING AND FINISHING Plate Rolling ...... 7-1 7 Slab Reheating ...... 7-1 Intermediate Edge Trimming ...... 7-1 Plate Finishing ...... 7-1 Solution Heat Treating and Quenching ...... 7-2 Plate Stretching ...... 7-2 Ultrasonic Inspection ...... 7-2 Artificial Aging ...... 7-3 Plate Edge Cutting ...... 7-3 Inspection , Superficial Defect Removal and Storage ...... 7-3 Self-Test Questions ...... 7-5

QUALITY AND PROCESS CONTROL Testing and Inspection ...... 8-1 8 Tensile Strength Testing ...... 8-1 Microscopic Inspection ...... 8-1 Porosity Testing ...... 8-1 Coolant / Lubrication Analysis ...... 8-2 Anodizing and Bright-Dipping Tests ...... 8-2 Dimensional Tolerance Control ...... 8-2 Surface Quality Characteristics ...... 8-2 Computerized and Centralized Controls ...... 8-3 Self-Test Questions ...... 8-5

GLOSSARY ...... 9-1 9 Self-Test Questions ...... 9-7

TECHNICAL APPENDICES Appendix A: Aluminum Alloy Designation System ...... 10A-1 10 Appendix B: Aluminum Temper Designation System ...... 10B-1 Appendix C: Typical Aluminum Alloy Properties ...... 10C-1 Appendix D: Aluminum Sheet & Plate Standards and Tolerances ...... 10D-1 Appendix E: Self-Test Questions (Technical Appendices) ...... 10E-1 Appendix F: Answers to All Self-Test Questions ...... 10F-1

REFERENCES ...... 11-1 11 INDEX ...... 12-1 12

Rolling Aluminum: From the Mine through the Mill 1 INTRODUCTION

APPLICATIONS In aircraft and spacecraft... in railcars, autos, trucks, trailers and boats... on skyscrapers and homes... in cans and cooking utensils... strong, lightweight aluminum plate, sheet and foil are vital materials of modern society.

I —Aluminum is an excel - Advantages of Aluminum Heat-conducting he properties of aluminum make it one of the lent heat conductor suitable for cooking ware and most advantageous and versatile materials in for heat exchangers; it is more efficient, pound for Tuse today. Aluminum is: pound, than copper. I I —Aluminum is also Lightweight —Aluminum and its alloys weigh Electrical conductivity only about one-third as much as equal volumes of an excellent conductor of electricity, commonly iron, steel or copper. used in such heavy-duty applications as high-volt - age transmission lines, bus bars and local and I Strong —Given appropriate tempers, some building distribution systems. aluminum alloys equal or surpass the strength of I some steels. Strong aluminum alloys can be as Corrosion resistant —Aluminum, exposed to much as two or three times stronger than steel for air, forms a transparent natural oxide film which the same weight . seals its surface against further reactions and protects it from corrosion from normal weather I Cryo-tolerant —In contrast to steel, titanium exposure. Specific aluminum alloys , treatments and many other materials that become brittle at and/or coatings may be selected to maximize very low ( cryogenic ) temperatures, aluminum corrosion resistance in particular applications. remains ductile and even gains strength as temper - I ature is reduced. This property makes aluminum Non-toxic —Rolled aluminum alloys are non- highly useful in very cold climates and for trans - toxic, easily cleaned, and non-absorbent. For these porting extremely cold materials such as liquefied reasons, they are widely used in food preparation natural gas (-260°F [-162°C]). and packaging . I I —Rolled aluminum does Ductile and workable —Aluminum alloys Non-combustible can be readily formed and fabricated by all stan - not burn, and it generates no hazardous emissions dard metalworking methods. when exposed to heat. It is safer than many other materials where fire is a potential hazard. I —Aluminum alloys can be joined by Joinable I all appropriate major methods, including welding, Recyclable —Aluminum’s resistance to cor- mechanical connections, and adhesive bonding. rosion and to reaction with most common materi - als keeps it in good condition throughout the life - I Reflective —Aluminum alloys with standard time of most products. Scrap aluminum is widely commercial finishes typically reflect more than 80 recycled, reducing demands for waste disposal percent of visible light and more than 90 percent and the environmental impacts of new material of infrared radiation, making aluminum an effec - production. tive reflector of, or shield against, light, radio waves and radiant heat. I INTRODUCTION 1-2

Flat-Rolled Aluminum Aluminum Plate Applications lat-rolled products — sheet, plate and foil — luminum plate can be formed directly into have, for many years, made up by far the strong shapes with uniform thickness. It can Flargest volume of aluminum products shipped aAlso serve as a “blank” from which complex large- annually in the United States, outstripping other area parts can be machined, such as the ribbed forms such as castings, extrusions, wire, rod and wing plates of advanced aircraft. It can be welded bar, forgings and impacts, and powders and paste. into large, strong, durable structures. Consumption of aluminum sheet and plate in Among many other applications, aluminum North America has generally increased over the plate is used to make railroad gondola and tank past 45 years. In 1960, sheet and plate consump - cars, battle armor for military tanks and vehicles, tion in domestic markets added up to 1.42 billion superstructures of large merchant and military pounds (645 million metric tons), or about 34.6% ships and offshore oil rigs, tanks for storing and of total aluminum product shipments. transporting super-cold liquefied natural gas, air - By 1980, in a rapidly growing market for alu - craft structural parts, and spacecraft components. minum, sheet and plate consumption was 5.56 bil - lion pounds (2,523 million MT) or 46.7%. Aluminum Foil Applications In 2005, domestic consumption of sheet and luminum foil is familiar to most people in the plate was 9.59 billion pounds (4,349 million MT), popular form of soft, very thin (0.00065 inch 41.5% of the total; including foil , flat- roll prod - [A0.0165 mm] thick) household kitchen foil : it’s ucts accounted for just under half (47.7%) of all easy to fold, impenetrable by water and vapor, fire aluminum products shipped that year. resistant, both heat-conductive and heat-reflective, and inhospitable to molds. But aluminum foil is also made of harder, Aluminum Sheet Applications luminum sheet is a remarkably versatile stronger alloys whose strength may approach that material, not only because of the custom- of steel. Atailored characteristics that it can be given in the The variety of properties available in aluminum rolling mill, but also because of its suitability to foils make them useful in applications ranging a wide range of finishing, fabrication and joining from the protective packaging of foods, pharma - processes. ceuticals and many other consumer products, to It can be given a wide variety of surfaces: pat- laminated vapor-barriers and insulation-backing terned, painted, plated, polished, colored, coated, in buildings, to artificial Christmas trees, sound laminated, anodized, etched or textured. It can be transducer/receiver diaphragms, rigid containers machined in different ways: sheared, sawed and and adhesive-bonded structural honeycomb. drilled. It can be easily formed: bent, corrugated, drawn or stamped. It can be readily joined to itself Specialty Products or to other materials: riveted, bolted, clinched, Special types of sheet and plate may be pro - brazed, soldered, welded and adhesively bonded. duced for particular applications. Some examples Its applications are too many to list completely. include: They include such familiar products as: light bulb Anodizing sheet Porcelain enameling bases, beverage and food cans, cooking utensils; Armor plate sheet home appliances; awnings and Venetian blinds; Brazing sheet Reflector sheet siding, roofing, flashing, gutters and curtainwall Decorative panel Rural roofing sheet panels for residential, commercial, industrial and sheet Tapered sheet and utility buildings; highway signs, license plates; Industrial roofing plate heat exchangers; automobile structures and exteri - sheet Tooling plate ors; truck, trailer and van panels; small boat hulls Lithography sheet Trailer roof sheet and aircraft skins. Painted sheet Tread plate Patterned sheet Vinyl-coated sheet I INTRODUCTION 1-3

Just a few of the hundreds of applications of rolled aluminum. I INTRODUCTION 1-4

DEFINITIONS All three are aluminum products that are rolled flat with a rectangular cross-section. They differ mainly in thickness. I Plate is aluminum rolled one-quarter inch produced in coiled or flat form, or in a (6.3 mm) thick or more. variety of special shapes or fabrications. Some Aluminum plate is a product that is rectangular in aluminum sheet producers can perform additional cross-section and form, and 0.250 inch (6.3 mm) processing or apply special surface treatments so or more thick. It may have sheared or sawed that the sheet product is suitable for the desired edges. It is usually produced in flat form (but can application. (Notes: When products are ordered be coiled) or in a variety of special shapes or to metric specifications using metric dimensions, fabrications. Some aluminum plate producers can sheet is defined as being > 0.20 mm to ≤ 6 mm perform additional processing or apply special thick. Sheet was previously defined as ≥ 0.006" surface treatments so that the plate product is (0.15 mm) through 0.249" (6.3 mm).) suitable for the desired application. (Note: When I products are ordered to metric specifications using Thinner than that, it’s “ foil .” Plain aluminum foil is a rolled product that is metric dimensions, plate is defined as being > 6 rectangular in cross section and ≤ to .0079 inch mm thick; however, the common US customary (0.20 mm) thick. It is available in coiled form or in reference thickness for 0.250" is 6.3 mm.) flat sheets. Some aluminum foil producers can per - I Under one-quarter inch (6.3 mm) down form additional processing or apply special surface to eight-thousandths of an inch (0.20 mm) treatments so that the foil product is suitable for the thick, it’s called “sheet.” desired application. (Notes: When products are Aluminum sheet is a product that is rectangular in ordered to metric specifications using metric cross-section and form, and of > 0.0079" (0.20 mm) dimensions, foil is defined as being ≤ 0.20 mm thickness through 0.249" (6.3 mm) thickness. It thick. Foil was previously defined as < 0.006" may have sheared, slit or sawed edges. It may be (0.15 mm) thick.)

ROLLING ALUMINUM: GENERAL DESCRIPTION Sheet, plate and foil are usually made by rolling thick aluminum between rolls that reduce the thickness and lengthen it, the way a baker rolls out pie crust. But rolling aluminum is a lot more complicated than rolling dough.

he actual passage of aluminum through a erties and other characteristics specified by each rolling mill is only one step — although the customer. cTentral one — in a comprehensive sequence. Each flat-rolled product owes its final properties not Aluminum Rolling: just to the rolling process itself but to its vital A Capsule History interactions with: the preparatory steps of alloy - luminum is a modern metal — discovered in ing, casting, scalping and pre-heating; intermedi - 1807, first isolated in 1825, produced in tiny ate annealing ; and such later finishing steps as aAmounts as a precious metal in 1845, and widely solution heat treatment or final annealing , stretch - commercialized only after the invention of the ing, leveling , slitting , edge trimming and aging . Hall-Heroult production process in 1886. Since Modern aluminum rolling plants conduct many, then, aluminum has rapidly grown to become the or all, of these operations, selecting, adjusting and second most heavily used metal in the world after coordinating them scientifically to produce flat- iron/steel. rolled products with the precise dimensions, prop - I INTRODUCTION 1-5

Floor plan, typical aluminum smelting plant

By the time aluminum arrived on the scene, early as 1917 (on the Junkers J-4 monoplane and mankind had thousands of years’ experience cast - the Dornier DO-1 biplane, forerunner of today’s ing and forging metals and several hundred years “stressed-skin” aircraft structures). of learning to roll them into sheets, plates and A practical method to produce Alclad sheet — even foils. Metal rolling may have been practiced strong aluminum alloy clad with a thin layer of a in developed countries as early as the beginning different aluminum alloy for enhanced corrosion of the 16th century. These familiar metal working resistance — was developed, in the United States, techniques were all adapted and applied to alu - in 1926. Since then, many other clad aluminum minum. products have been developed for such purposes The first aluminum stew pan was stamped in as corrosion protection, surface appearances, or 1890, and most of the aluminum produced before ease of brazing. 1900 was used in cooking utensils. Aluminum hulled boats were built in the 1890s, including the U.S. racing yacht “Defender”, with Technological Advances he fundamental principles and designs of metal aluminum plates, in 1895. rolling mills had been established by the end of By 1903, some 6.5 million pounds (3 million the 19th century, but improvements in their kg) of aluminum was consumed annually, about T one-third of it in the form of sheet. technology and metallurgy have continued In that same year aluminum foil was first rolled, throughout the 20th century. in France; aluminum foil -rolling in the United Aluminum rolling has gained steadily in both States began in 1913, for wrapping candy and quality and efficiency through advances in its own chewing gum specific technology as well as improvements Thin aluminum skins appeared on aircraft as applied to metal rolling in general. I INTRODUCTION 1-6

Floor plan, typical aluminum rolling plant.

Hot and cold continuous sheet rolling mills coolant /lubricant application; and many other came into operation in the United States in 1926. technical advances. The maximum speed of the first U.S. cold “ strip ” In recent years, aluminum rolling mills have mill was reported to be only about 200 feet per been introducing computerized process control , minute (60 m/min.); modern cold mills operate quality control and inventory tracking, and about 35 times faster! advanced gauge and shape controls, to achieve The rolling industry switched from steam even higher product quality and consistency. engines to electric power; it built specialty mills, Computerization, in turn, is pointing the way to and bigger multi-purpose mills. such further developments as Computer Integrated The standard “two-high” and “four-high” mill Manufacturing ( CIM ), Statistical Process Control configurations that were brought into early use, (SPC), and Just-In-Time (JIT ) production sched - with mill rolls “stacked” vertically, are still basic ules. These recent advances are designed to to the rolling industry. They were later supple - increase product quality and delivery reliability mented, however, by various “cluster” designs and to reduce production costs. with work rolls supported by two or more back-up rolls each, as explained in Section 4. Aluminum that starts out two feet (0.6 m) Over the decades, safety, efficiency, cost and thick may travel a mile (1.6 km) through product quality were improved by the introduction large rolling mills, furnaces, cutters and of automatic material handling devices, manipula- stretchers, to emerge as thin sheet only tors, guides, guards, lifting and tilting tables; auto- a few hundredths of an inch (a few matic roll changers, compact load-measuring cells tenths of millimeters) thick... And it’s had on roll bearings, gauge control feedbacks, load a long journey before it even reaches equalization and overload protection; programmed the rolling mill. I INTRODUCTION 1-7

SELF-TEST QUESTIONS 1.8 Name five applications of aluminum plate. SECTION 1: INTRODUCTION

1.1 Name any five important advantages of rolled aluminum products. 1.9a In US customary units “plate” means a rolled product… a. less than 6 inches thick. b. greater than one-tenth inch thick. c. greater than or equal to one-quarter 1.2 Aluminum resists atmospheric corrosion inch thick. because: d. exactly 0.250 inch thick. a. It is always painted or coated. b. It has a naturally stable oxide film. 1.9b In metric units “plate” means a rolled c. It is a good heat conductor. product… d. It is non-combustible. a. greater than 6 mm thick. b. greater than 2.5 mm thick. 1.3 Aluminum weighs about as much as an c. less than 150 mm thick. equal volume of iron, steel or copper. d. exactly 6 mm thick. a. Three-quarters. b. One-half. 1.10a In US customary units “sheet" means a c. One-third. rolled product... d. One-quarter. a. from .010 to .200 inch thick. b. from .008 to .249 inch thick. 1.4 High- strength aluminum alloy can be... c. from .001 to .249 inch thick. a. up to half as strong as d. from .006 to .490 inch thick. b. up to 90% as strong as c. just about as strong as 1.10b In metric units “sheet” means a rolled d. stronger than product... a. from 0.25 to 5 mm thick. …an equal weight of steel. b. from 0.025 through 6 mm thick. c. from 0.20 through 6 mm thick. 1.5 As temperature is reduced, the strength d. greater than 0.20 up to 12 mm thick. of aluminum... a. decreases. b. remains the same. 1.11 Air conditioner fin stock produced as a c. increases. coil product, for example, .0045-inch (0.115 mm) thick falls into the category 1.6 The largest volume of aluminum products of... shipped annually in the United States a. sheet. consists of… b. plate. a. castings. c. foil . b. rolled products. c. forgings and impacts. Why? d. wire, rod and bar.

1.7 Name five applications of aluminum sheet. I INTRODUCTION 1-8

1.12 The existence of aluminum as a metal 1.15 Aircraft skins made of aluminum was first discovered... sheet appeared as early as... a. in prehistoric times. a. 1903. b. around 700 B.C. b. 1917. c. in 1725 (A.D.). c. 1931. d. in 1807. d. 1942. e. in 1903. 1.16 The basic principles and designs of 1.13 The Hall-Heroult process was metal rolling mills had been invented... established by... a. in 1807. a. the end of the Roman Empire. b. in 1825. b. the end of the Renaissance. c. in 1845. c. the end of the 19th century. d. in 1886. d. the middle of the 20th century.

1.14 Most of the aluminum produced before 1900 was used in: a. Military armor. b. Vehicles. c. Cooking utensils. d. Architecture. e. Boat hulls. Rolling Aluminum: From the Mine through the Mill 2 PRODUCTION of Aluminum Alloys : From Mine to Mill BAUXITE MINING Aluminum ore, the mineral bauxite , is mined in many countries around the world, and is crushed and refined to yield alumina — nearly pure aluminum oxide .

luminum is one of the most abundant ele - which may contain 40 to 60 percent impure ments on earth. It is estimated that the solid hydrated aluminum oxide — that is, aluminum Aportion of the earth's crust to a depth of ten miles oxide to which water molecules have become is about 8% aluminum, surpassed only by oxygen attached. The other components of bauxite typi - (47%) and silicon (28%). Aluminum is a major cally include various amounts of iron oxide, sili - constituent of clay and almost all common rocks. con oxide, titanium oxide and water. Its texture Aluminum is never found as a pure metal in can range from crumbly to something like lime - nature, but only in chemical compounds with stone, and its color varies from off-white to rusty- other elements — and especially with oxygen, red, depending on its iron oxide (rust) content. with which it combines strongly. The richest and most economical bauxite ores Feldspars, micas and clay contain aluminum ox- are often found close to the earth’s surface in trop - ide (A1 203), also known as alumina , in concentra- ical and subtropical areas. Worldwide reserves of tions ranging roughly between 15 and 40 percent bauxite ore are estimated to be very large: enough by weight . high grade ore to last perhaps 300 to 500 years, and enough lower-grade ore for another 500 years at recent consumption rates. Clays and other min - erals could, if necessary, provide an almost limit - less source of alumina . Mining methods may vary, but most bauxite is mined in open pits by conventional digging machin- ery, and then is crushed, washed and dried in prepa- ration for separation of the alumina from the other, undesirable components. Subsequent to the mining operation, the aluminum industry spends consider - able effort to the restore the land and its flora and fauna back to their original condition.

ALUMINUM REFINING ost alumina is refined from bauxite by the Bayer process , patented in Germany by Karl Josef Bayer in 1888. This process is carried out in *Others includes 2.1% Magnesium, 2.6% Potassium, M 2.8% Sodium, 3.6% Calcium, 5% Iron, and 0.14% four steps: Titanium, Manganese, Nickel, Copper, Zinc and Lead. 1. The crushed, washed and dried bauxite is Main elements found in the earth’s crust. “digested” with caustic soda (sodium hydroxide) Most aluminum is produced from an ore called at high temperatures and under steam pressure, bauxite (named after the town of Les Baux in dissolving the alumina in a mixture with undis - southern France where it was discovered in 1821), solved impurities called “red mud.” I PRODUCTION 2-2

2. This mixture is fil - tered to remove the red mud, which is discard - ed. The clarified alumi - na solution is trans - ferred to tall tanks called “precipitators.” 3. In the precipitator tank, the hot solution is allowed to cool with the addition of a little aluminum hydroxide to “seed” —that is, stimu - lat e— the precipitation of solid crystals of alu - minum hydroxide and sodium hydroxide. The aluminum hydroxide settles to the bottom and is removed from Bauxite mining . the tank. granulated sugar but is hard enough to scratch glass. The widely-used abrasives corundum and 4. The separated aluminum hydroxide is washed emery are forms of alumina . to remove residues of caustic soda and then is heated to drive off excess water in long rotating Refined alumina consists of about equal weights kilns called “calciners.” Aluminum oxide (alumi - of aluminum and oxygen, which must be separat - na ) emerges as a fine white powder that looks like ed in order to produce aluminum metal.

ALUMINUM REDUCTION: THE HALL-HEROULT PROCESS A practical way of breaking down the aluminum oxide — the Hall-Heroult process — was invented in 1886. Another mineral, cryolite , is melted, and the aluminum oxide is dissolved in it. Electric current passed through the bath attracts the oxygen to carbon anodes. The carbon and oxygen form carbon dioxide, which bubbles out of the bath. Molten aluminum is left behind at the bottom of the reducing cell, or “ pot .” It is siphoned into a crucible for transport to the casting foundry. The process is continuous, and a typical pot may produce about 1400 pounds of aluminum daily. Hundreds of cells on the same electrical circuit form a potline .

luminum and oxygen form such a strong Chemical methods of breaking down aluminum chemical bond that it takes a very large oxide were developed in the mid-19th century but aAmount of energy to separate them by “brute were so expensive that metallic aluminum cost as force” methods like heating. Although aluminum much as silver. The small amounts of aluminum as a pure metal melts at about 1220°F (660°C); that were produced were used mainly for jewelry aluminum oxide requires a temperature of about and other luxury items. 3660°F (2015°C) before it will melt. Early researchers thought of using electricity to I PRODUCTION 2-3

separate aluminum from its oxide in solution but were frustrated by seemingly high energy require- ments; the inadequacy of their only sources of elec- tricity — batteries; and the insolubility of alumina in water. The invention of the rotary electric generator, the dynamo, in 1866 solved part of that problem. The other part was not solved until 1886 when Charles Martin Hall in the United States and Paul L.T. Heroult in France discovered the answer almost simultaneously. Hall and Heroult found that alumi - na would dissolve in a molten mineral called cryo - lite (a sodium aluminum fluoride salt) at about 1742°F (950°C). In solution, the aluminum oxide Charles Martin Hall (left) and Paul L.T. Heroult. is readily separated into aluminum and oxygen by They found the key to modern aluminum electric current. production. Other solvents might have worked in theory. Cry- the solution molten. olite , however, has the practical advantages of sta- Oxygen atoms, separated from aluminum oxide , bility under process conditions and a density lower carry a negative electrical charge and are attracted than that of aluminum, allowing the newly-forming to the positive poles in each pot . These poles, or metal to sink to the bottom of the “reduction cell.” anodes, are made of carbon which immediately The Hall-Heroult process takes a lot of electricity combines with the oxygen, forming the gases car - but only a low voltage, so it is practical to connect bon dioxide and carbon monoxide. These gases many reduction cells, or “pots”, in series along one bubble free of the melt, leaving behind the alu - long electrical circuit, forming a “ potline .” Modern minum which collects at the bottom of the pot . cells are operated with currents of around 250,000 The process, therefore, steadily consumes the amperes but at only four or five volts each. Such carbon anodes, which must be renewed either by cells use about six or seven kilowatts of electricity regular replacement or by continuous feeding of a per pound of aluminum produced. self baking paste (Soderberg anode ). About one- The heat generated by electrical resistance keeps half pound (225 g) of carbon is consumed for every pound (455 g) of aluminum produced. Most alu - minum reduction plants include their own facilities to manufacture carbon anodes, each of which may weigh 600 - 700 pounds (270 - 320 kg) and must be replaced after about 14 days of service. The negative electric pole, or cathode, forms the inner lining of each pot . It is also made of carbon. As a cathode it does not react with the melt, so it has a long service life. As alumina is reduced to aluminum and oxygen, fresh alumina is added to the molten bath to contin - ue the process. Aluminum fluoride is also added when necessary to maintain the bath's chemical composition, replacing aluminum fluoride lost by reactions with caustic soda residues and airborne moisture. Modern smelters capture and recycle flu - orides and other emissions. When sufficient molten aluminum has collected at the bottom of a pot , it is siphoned into a crucible for transport to alloying and c asting facilities. The aluminum produced by the Hall-Heroult process is more than 99 percent pure . Potline I PRODUCTION 2-4

Main steps in the Bayer alumina -refining process and the Hall-Heroult aluminum-reduction process. I PRODUCTION 2-5

ALLOYING In the melt house, the aluminum is poured into a remelt furnace for alloying and fluxing .

Adding small amounts of other elements to pure aluminum produces strong alloys , which can be further conditioned by heating, cooling and deformation treatments called “tempering.”

lloying requires the thorough mixing of Each alloy is assigned a four-digit number, in aluminum with other elements in liquid — which the first digit identifies a general class, mAolten — form. This may be done in different or “series”, characterized by its main alloying ways, depending on the sources of aluminum elements: used. I include aluminum of Newly-produced aluminum may be transferred, 1xxx Series alloys 99 percent or higher purity. They have excellent still liquid, from the Hall-Heroult reduction cells corrosion resistance and thermal and electrical into a “holder” or reservoir furnace where solid conductivity. alloying elements are added, to dissolve and mix I into the melt. 2xxx Series alloys have copper as their princi - Solid scrap aluminum, from fabrication opera- pal alloying element, often with smaller amounts tions or recycled products, must be melted in a of manganese and magnesium, and can be “remelt” furnace before its alloy composition is strengthened substantially by heat treatment. adjusted as necessary. Then the recycled, re- I 3xxx Series alloys have manganese as their alloyed scrap is transferred to a holder. major alloying element, sometimes with smaller Often, new aluminum is alloyed with scrap alu- amounts of magnesium, and are generally non- minum of known composition. The solid scrap is heat-treatable. added to the molten new aluminum, and then fur - I 4xxx Series alloys , alloyed mainly by silicon, ther alloying elements are added to the mixture as are usually non-heat-treatable. needed to adjust its final composition. I Most melting furnaces are large (capacity as 5xxx Series alloys contain magnesium as much as 200,000 pounds (90,000 kg) or more) their main alloying element, often with smaller and are oil- or gas-fired. They can accept molten amounts of manganese and/or chromium. These metal and alloying ingredients in addition to scrap alloys are generally non-heat-treatable. at a temperature around 1400°F (760°C). For I 6xxx Series alloys contain silicon and magne- certain melting needs, the furnace is smaller, has a sium in proportions that will form magnesium sili- lower melting rate and may be electrically heated cide and are heat-treatable. to minimize oxidation of light gauge (thin) scrap I alloys are alloyed mainly by zinc, or to control emissions. The molten metal is then 7xxx Series often with smaller amounts of magnesium and transferred to a holder. sometimes copper, resulting in heat-treatable After alloying, the molten metal is cleaned and alloys of very high strength . fluxed to remove impurities and hydrogen gas I before being transferred to the casting pit. The 8xxx Series of alloy numbers is reserved for alloys of various other compositions. Aluminum Alloy Series luminum alloys are registered according to The aluminum alloy designation system is ex- their composition. For most of the world, alu - plained in greater detail in Section 10, Appendix Aminum alloy formulations are registered with the A. Section 10, Appendix C contains tables of typi - Aluminum Association under a numerical classifi - cal mechanical properties, physical properties, and cation system. comparative characteristics and applications. I PRODUCTION 2-6

HEAT-TREATABLE ALLOYS Some alloys , usually in the 2xxx, 6xxx, and 7xxx series, are “solution heat treatable”. They can be strengthened by heat - ing and then quenching , or rapid cooling. They may be fur - ther strengthened by “cold working” controlled deformation at room temperature. ome aluminum alloys can be significantly solubility in aluminum with increasing temperature. hardened and strengthened by controlled heat - The increase of strength induced by heat treat- iSng and quenching sequences known as “heat ment can be dramatic. For example, in the fully treatment” followed by natural or artificial aging annealed O- temper , aluminum alloy 2024 has an (“ precipitation hardening ”). Such alloys are called ultimate yield strength of about 27,000 pounds per “heat-treatable.” square inch (185 MPa). Heat treatment and cold Most heat-treatable aluminum alloys contain working followed by natural aging (T3 temper ) magnesium, plus one or more other alloying ele - increases its strength 2 1/2 times, to 70,000 ments such as copper, silicon and zinc. In the pounds per square inch (480 MPa). As strength is presence of those elements, even small amounts increased by heat-treating, formability is affected of magnesium promote precipitation hardening . in the other direction: for example, alloy in the T3 These alloys respond to heat treatment because temper is less formable than “fully soft” alloy in their key alloying elements show increasing solid the O- temper .

NON- HEAT-TREATABLE ALLOYS “Non-heat-treatable” alloys can be tempered only by cold working and annealing operations. lloys which will not gain strength and hard - in non- heat-treatable alloys . For example, the ulti- ness from heat treatment are called “non-heat- mate tensile strength of alloy 3003 is increased Atreatable.” from about 16,000 pounds per square inch (110 The initial strength of these alloys , usually in MPa) in the O- temper to 29,000 pounds per the 1xxx, 3xxx, 4xxx, and 5xxx series, is provided square inch (200 MPa) in the H18 strain hardened by the hardening effect of their alloying elements. temper . The ultimate tensile strength of alloy 3004 Additional strengthening can be created by cold is increased from about 26,000 psi (180 MPa) in working — deformation which induces strain- its O-temper to about 41,000 psi (280 MPa)in the hardening , denoted by the “H” tempers. Strain- H38 temper (strain-hardened and stabilization hardened alloys containing appreciable amounts heated). of magnesium are usually given a final elevated Both heat-treatable and non- heat-treatable alloys temperature treatment to stabilize their properties. may be deliberately softened and made more Cold-working can increase strength significantly formable by annealing .

Aluminum for rolling must be alloyed to exacting specifications. It must be suitable for the planned rolling, for tempering, and for its intended end use.

Equally important is freedom from impurities that might weak en the alloy, cause mechanical defects, or damage mill rolls. I PRODUCTION 2-7

RECYCLED ALUMINUM SCRAP In the remelt furnace compatible aluminum scrap is added to the pure aluminum , from “charge buckets” moved by overhead cranes.

Recycled scrap makes up more than half of the aluminum alloy processed in the United States; and recycling uses 95 percent less energy than making new aluminum. ecycled beverage cans are not only a large Aluminum scrap generated within the rolling source of aluminum scrap but also a particular - plant itself is also returned to the melting hearths; Rly convenient one because of the known uniformi - this in-house scrap is also very convenient ty of their alloy composition. They can be recy - because its alloy composition is exactly known. cled right back into new sheet ingot for canstock, Similarly, scrap returned from fabricators often as well as other products. Some specialized plants consists of uniform loads of identified alloys . produce aluminum sheet ingot only from used alu - Other scrap from various recycled products is minum beverage cans, providing very efficient, also used for alloying, taking into account its alloy energy-saving “closed-loop” recycling . composition, determined by testing.

ADDITION OF ALLOYING ELEMENTS Next, selected elements — such as magnesium, silicon, manganese, zinc or copper — are mixed in to achieve the correct alloy composition. agnesium, silicon and zinc are usually added the melt. Copper is added in either pure (shot / as pure ingredients. Chromium, manganese chopped wire / etc.) or alloyed forms. Titanium aMnd iron are usually added as briquettes contain - and zirconium are typically added as either 5-10% ing up to 85% pure metal, balance being alu - alloy or as compacted, 95% pure “hockey pucks”. minum foil and binders, to facilitate mixing with I PRODUCTION 2-8

NOTES I PRODUCTION 2-9

SELF-TEST QUESTIONS 2.8 Pure aluminum melts at about… a. 660°F SECTION 2: PRODUCTION b. 660°C c.1220°F 2.1 Aluminum makes up about_____of the d.1220°C earth’s crust. a. 8%. 2.9 Aluminum oxide melts at about… b. 15% a. 212°F (100°C). c. 28% b. 660°F (350°C). d. 47% c. l000°F (540°C). d. 3660°F (2015°C). 2.2 Aluminum is_____found as a pure metal in nature. 2.10 The main factor which induces the a. always release of metallic aluminum from b. sometimes aluminum oxide is… c. never a. heat. b. electricity. 2.3 Economically mined bauxite contains c. water. what percentage of aluminum oxide ? d. None of the above. a. 40-60% b. 25-40% 2.11 The modern Hall-Heroult reduction c. 15-25% process utilizes... a. heat. 2.4 Most bauxite is mined... b. dissolving medium. a. in deep tunnels. c. electric current. b. in open pits. d. a, c c. in rock quarries. e. b, c d. in shallow river bottoms. f. a, b, and c. 2.5 “Alumina ” is another name for... 2.12 In the Hall-Heroult reduction process, a. aluminum. what substance combines with the b. bauxite . oxygen in Al O to leave molten c. aluminum oxide . 2 3 aluminum? d. aluminum alloy. a. Feldspar b. Cathode 2.6 Most alumina is refined by… c. Carbon a. the Karl process. d. Hydrogen b. the Hall process c. the Heroult process. 2.13 Cryolite is… d. the Hall-Heroult process . a. a popular aluminum alloy. e. the Bayer process . b. a sodium aluminum fluoride salt. c. the material of aluminum reduction 2.7 Refined alumina contains what propor - anodes. tion of aluminum by weight ? d. None of the above. a. about two-thirds b. about one-half 2.14 A typical modern Hall-Heroult cell uses c. about one-quarter about how many kilowatts of electricity d. None. to produce one pound (455 g) of alu - minum? a. One or two b. Six or seven c. Ten or twenty d. Trick question: no electricity. I PRODUCTION 2-10

2.15 The cathodic lining of an aluminum 2.22 “Solution heat-treatable” alloys are reduction pot has a long service life those which… because… a. can stand high temperatures without a. it is made of brick. melting. b. it is not in direct contact with the b. can be brightened by heating. melt. c. can be dissolved at high tempera - c. it does not react with the melt. tures. d. it plays no role in the reduction d. can be strengthened by heating and process. quenching .

2.16 Molten aluminum is removed from a 2.23 Solution heat-treatable alloys are usually reduction “ pot ” by… in the… a. siphoning. a. 2xxx, 6xxx and 7xxx series. b. pouring. b. 2xxx, 4xxx and 5xxx series. c. ladling. c. 1xxx, 5xxx and 6xxx series. d. pumping. d. 2xxx series only.

2.17 Aluminum produced by the Hall-Heroult 2.24 “Non-heat-treatable” alloys are those process is… which… a. a high- strength alloy. a. can be strengthened only by low b. about 75% pure aluminum . temperatures. c. exactly 89% pure aluminum . b. can be strengthened only by cold d. more than 99% pure aluminum . working. c. can be strengthened by annealing . 2.18 “The most important reason for having d. risk cracking when heated. remelt furnaces in a rolling facility is to recycle generated process scrap.” 2.25 Non- heat-treatable alloys are usually in This statement is: the… a. True. a. 1xxx series. b. False. b. 3xxx series. c. 4xxx series. 2.19 What is the approximate temperature in d. 5xxx series. a melting furnace? e. All of the above. a.1000°F (540°C). b.1400°F (760°C). 2.26 An element which never plays a major c.1800°F (980°C). part in the preciptiation hardening of heat-treatable aluminum alloys is… 2.20 Wrought aluminum alloy series numbers a. copper. always have how many digits? b. manganese. a. Three. c. zinc. b. Four. d. silicon. c. Five. e. magnesium. d. As many as necessary. 2.27 “Only solution- heat-treatable alloys can 2.21 The different aluminum alloy series are be made more formable by annealing .” characterized by… This statement is: a. alloy strength . a. True. b. aluminum content. b. False. c. alloy composition. d. (None of the above). I PRODUCTION 2-11

2.28 Remelting and alloying scrap aluminum 2.29 The melt is transferred into a holding uses about as much energy as smelting furnace before casting in order to… new aluminum. a. add more scrap. a. 5% b. adjust alloy composition. b. 50% c. remove hydrogen . c. 100% d. a and b. d. 150% e. b and c. f. a and c.

Rolling Aluminum: From the Mine through the Mill 3 PREPARATION of Aluminum Alloys for Rolling

METAL CLEANING: FLUXING AND FILTRATION Then the molten alloy is “fluxed”: nitrogen and chlorine gases are injected, and their bubbles bring impurities to the surface to be skimmed off by a furnace operator. aterials charged into an alloying furnace this purpose to avoid altering the chemical com - often carry with them some unavoidable for - position of the alloy. However, small amounts of Meign matter, and other non-metallic materials may chlorine or other reactive gases, typically less than be generated by chemical reactions. These sub - 10 percent, may be mixed with the inert gases stances, which could otherwise cause problems in in order to react with certain impurities such as later operations and impair product quality, are sodium, calcium or lithium and form compounds removed from the alloy by fluxing and filtration . which can be removed by skimming or filtration . Even though chlorine will have a tendency to Fluxing react and preferentially remove magnesium, it luxing ” refers primarily to the removal does offer the most efficient way to remove of dissolved hydrogen gas from molten hydrogen through a chemical reaction in contrast “Faluminum alloy by bubbling gases through it. to a much slower diffusion process inherent to However, the bubbling gases also “sweep” some inert gases. Due to environmental and other con - solid impurities to the surface where they collect cerns the use of chlorine is being reduced, and in as a frothy dross which is removed. some regions its use is prohibited. Hydrogen gas — derived from airborne water Typical fluxing techniques include porous plugs vapor, from materials added to the melt, or from located in the bottom of the furnace, spinning furnace walls, tools, or anything else that comes rotors and fluxing wands (ceramic c oated metal in contact with the melt — dissolves readily in tubes which incorporate porous plugs at the end of molten aluminum. But it is only about 5% as the tube). All of these techniques are designed to soluble in solid aluminum. If it were allowed to promote uniform distribution of fine bubbles which remain while the molten metal is cast, it would enhance diffusion and chemical reaction processes. emerge during solidification to form tiny bubbles: Fluxing may be done in the holding furnace or in blisters which mar the surface, or internal pores a special in-line device between the furnace and the which weaken the product. casting station, separately or in conjunction with Before casting, dissolved hydrogen is removed filtration . by bubbling dry, hydrogen -free gases through the In-line degassing can be used as the only means molten aluminum. Hydrogen dissolved in the alu - of hydrogen removal, or it can be a part of a com - minum diffuses into these other gases and is car - prehensive approach which includes furnace fluxing ried out of the melt by the rising bubbles. Inert and ceramic foam or other rigid media filtration . (nonreactive) gases, chiefly nitrogen, are used for

ALLOY SAMPLE ANALYSIS Now a small sample of the alloy is cast and is analyzed within minutes by the lab.

t the holding hearth and during casting, a solid disk about two inches (50mm) in diameter, small amount of molten alloy is scooped up called a “button”. wAith a ladle and poured into a small mold where it This “button” is identified with the number of cools and hardens in about 15 to 20 seconds into a its alloy batch and is sent to the plant laboratory I PREPARATION 3-2

for analysis. Laboratory analysis may be done The analyzer may be linked with a computer automatically by a device called a spectrometer which automatically registers the batch number or quantometer. The alloy button is placed in a and its specified alloy composition, compares it chamber in the device. Then a high-voltage spark with the actual sample analysis, and issues a instantly vaporizes a tiny amount of material from “pass” message when the alloy is within specifica - the surface of the sample and momentarily tions or an “off-analysis” message if it is not. excites, or energizes, the atoms in this alloy vapor. The results may be returned automatically to The excited atoms immediately radiate away the the hearth operator by instantaneous electronic excess energy, returning to their normal state. communication. Thus, a “rush” request for analy - Each atom radiates excess energy in a pattern, a sis can be answered within a few minutes from spectrum, unique to its element. By detecting and the time the button sample leaves the hearth area. measuring the emitted energy patterns, the spec - If the alloy is found to be “off analysis”, ele - trometer identifies each element present and its ments may be added to correct its composition. It proportion in the alloy sample. will then be retested for approval. If batch correc - A single “shot” in the high voltage spark spec - tion is not practical, off analysis alloy is recycled. trometer is usually completed in about 25 seconds including the set-up time. A series of four shots on If its composition is correct, the alloy one sample can be completed in two or three min - moves to a holding furnace for cast - utes. ing; if not, if is corrected and retested.

FILTRATION Before casting, aluminum flows through a filter to remove any remaining particles. ny foreign particles or inclusions that have They are typically 16" (400 mm), 20" (500 mm) escaped the fluxing process or have devel - or 24" (600 mm) square and approximately 2" Aoped afterward must be removed from the molten (50 mm) thick. These filters have pore sizes which aluminum alloy before it is cast into rolling ingot . range from 20 per inch (8 per cm) for capturing Inclusions , hard or soft, might weaken the final coarse impurities to 70 per inch (30 per cm) for product, show up as streaks or flaws in its surface, removal of very fine particulates. or damage work roll surfaces. Filtration is per - During the past 25 years another group of filters formed to remove these potentially harmful parti - was developed. They use spinning nozzle technol - cles. Filtration is sometimes performed in combi - ogy. Each of these filters consists of two or three nation with the fluxing step, within the same chambers. Each chamber is equipped with a process unit. spinning nozzle which delivers a fine dispersion Filtration may utilize deep bed filters which are of gas bubbles. It is very similar to the fluxing used for multiple casts and typically consist of process in the holding furnace except that argon 5 to 15" (125 – 380 mm) layers of media such as with up to approximately 3% chlorine is used for sintered high density alumina flakes or spheres flotation (removal) of small particulates and with diameters in the range of .25 to .75" (6 – 19 hydrogen . While the material is flowing through mm). Molten aluminum flows through the deep the chambers, particulates are captured and float bed which captures and retains nonmetallic and to the surface while at the same time hydrogen is similar fine particulates. also removed. Some of the more commonly used Another method utilizes disposable rigid media types are SNIF, ALPUR and LARS. filters which have the morphology of a sponge. I PREPARATION 3-3

ADDITIVES Along the way, additional elements may be fed in; titanium is often added to help prevent cracking during solidification or for grain refinement. ately before casting, and the most commonly used he addition of small amounts of titanium additive form is 3/8" (10 mm) diameter rod. (usually in combination with either boron Typical grain refiners are 5%Ti /0.3% Boron or or carbon) to molten aluminum alloy as a grain - T 5% Ti/0.15% C alloys . For example, a solid rod of refiner is widely practiced in the rolling industry. these grain refiners may be fed into the molten Dissolved in the alloy, titanium carbide or titani - stream of aluminum at a controlled rate en route um diboride particles provide numerous “ nucle - to casting. The addition levels are quite low, ation points” where solidification begins during typically less than 0.01 weight percent. cooling. This enhances uniformity, disperses Grain refiner is added “at the last minute” stresses throughout the solidifying aluminum, because it is most effective if its first five minutes and reduces stress-induced cracking. in the aluminum alloy take place during alloy From its holding hearth, molten aluminum is solidification. Longer residence in molten alloy poured through a trough into the ingot -casting would give the grain refiner time to coalesce into mold. The grain refiner is usually added immedi - larger particles, reducing its effectiveness.

CONTINUOUS CASTING OF SHEET OR PLATE Aluminum sheet can be continuously cast for a variety of applications. This production method reduces the steps to produce the sheet. The continuous casting process is used for a variety of common aluminum applications. Currently about 20% of the North American sheet and plate production is produced by this method. The reduction in hot working is a result of the ontinuous casting takes molten metal and reduced casting thicknesses seen in continuous solidifies it into a continuous strip . A vari - casting. Although actual thicknesses vary by eCty of methods are used to solidify the metal, method and producer, “as-cast” continuous cast including roll casters, belt casters and block cast - strip is less than 1 inch (25 mm) thick, compared ers. The common feature for all of these methods to the 30+ inch (760+ mm) thick ingot produced is that sheet is taken directly from molten metal, via the DC ingot process. solidified, and coiled in one operation. In many Because it is much thinner than ingot , continu - cases, the strip is run through a hot mill (which ously cast strip cools and solidifies much faster may have more than one stand). than DC ingot ; this may produce greater supersat - Three significant differences between continu - uration of alloying elements and less segregation ous casting and the more traditional DC ingot of these elements within metal grains. In effect, casting (see next section) are: continuously cast strip is partly pre-homogenized. I Significantly reduced hot working in continu - In addition, the rapid cooling of continuously ous casting compared to DC ingot casting. cast strip minimizes the tendency of alloying elements to concentrate at the surfaces and makes I No homogenization between casting and hot scalping unnecessary, so these products can move rolling . directly to rolling. I No scalping between casting and hot rolling . The lack of homogenization and reduced hot working does result in different metallurgical structures even in similar alloys . As a result, I PREPARATION 3-4

continuously cast alloys may have different Roll Casters capabilities than their DC counterparts. he roll caster is the most common form of strip Producers of continuous cast sheet have estab - casting: molten aluminum flows from nozzles lished practices to ensure comparable performance bTetween a pair of water-cooled rolls. In contact in their chosen markets. In some applications, with the rolls, it solidifies at a cooling rate however, efforts to make continuous cast products between 100 and 1,000°F per second (55 – as formable as their DC ingot counterparts may 555°C/sec.). In addition, the newly solidified significantly reduce the advantages of the continu - metal undergoes some hot deformation as it passes ous casting process. through the roll gap . There are many markets where continuous cast Typical roll casters can produce continuous products are found, including (but not limited to): sheet in the range of 30 to 80 inches (760 – 2030 I Building and Construction Applications mm) wide, at linear speeds ranging from about 6 to 10 feet per minute (2 – 3 m/min.). Their pro - I Foil and Fin Stock ductivity rates are generally in the range of 60 to I Food and Beverage Containers 100 pounds of product per hour, per inch of width (10 – 18 kg per hour per cm of width). I Truck and Trailer applications I General Distribution Slab Casters lab casters produce continuous aluminum prod - ucts in the plate thickness range. These prod - Types of Continuous Casters ontinuous casters are generally described by uScts do not undergo any hot deformation in the the type of product they yield (“ strip ” or caster. They emerge with as-cast metallurgical “Cslab ” casters), or by the type of equipment used characteristics and must be rolled by hot mills to (for example — roll , belt or block casters). achieve wrought aluminum properties and a sheet Both strip (continuous sheet) and slab (continu - gauge that can be coiled. ous plate) casters have been in use since the They produce slab typically between 10 and 80 1950s. They are less versatile in product thick - inches (255 – 2030 mm) wide, at linear speeds nesses and characteristics than conventional mills around 20 feet per minute (6 m/min.), yielding which flat- roll aluminum ingot , but they require productivities in the range of 1,000 to 1,300 lower capital investment and have found economi - pounds per hour, per inch of width (180-225 kg cal application primarily in conjunction with lim - per hour per cm of width). ited-purpose “minimills.” There, one of their main Slab casters cool and solidify molten aluminum advantages — particularly in slab casting — is the at rates ranging from 1 to 10°F per second (1/2 to ability to produce a continuous band, which can 5°C); solid slab emerges at a temperature of about move immediately through a hot-rolling mill for 1,000°F (540°C), requiring little or no reheating transformation into thinner wrought products in an before hot rolling . unbroken flow. The two main commercial types of slab casters Continuous casting processes are undergoing are belt and block casters. further technical development aimed at increasing their speed and versatility. Belt Casters n the belt caster, molten aluminum flows between two almost-horizontal, continuous, thin Strip (Continuous Sheet) Casters trip casters can produce continuous aluminum mIetal belts that are in constant motion. Metal side sheet thin enough to be coiled immediately dams moving with the belts contain the aluminum aSfter casting, without additional rolling. This while it solidifies. The belts are usually inclined at coiled sheet may be re-rolled later into thinner an angle of 5 to 9 degrees from horizontal, to min - sheet gauges. Alternatively, the cast sheet may imize turbulence in the pool of molten aluminum, be fed immediately through a hot-rolling mill for and belt speed is synchronized with the metal thickness reduction before the product is coiled. flow rate. The hot metal transfers its heat through films of I PREPARATION 3-5

lubricant to the metal belts, which are water-cooled As this loop belt rotates around its drive gears, on their outer sides, producing slabs typically in each block takes its turn lining up with its neigh - the range of 1/2 to one inch (12 – 25 mm) thick. bors to contain the flow of molten aluminum from This continuous slab is usually fed directly into a nozzle. The blocks above and below the alu - low-speed in-line rolling mills which reduce it to minum absorb enough heat to solidify the alloy as coils of thinner sheet stock for eventual re-rolling. they travel along with it. Then, as they reach the farther drive gears, each block lifts away from the aluminum and moves around to the far side of its loop where a cooling system removes the heat before the block swings back for another turn in the traveling mold wall. As with belt casters, the continuous slab pro - duced by the block caster is usually hot-rolled immediately into thinner sheet stock.

Belt Caster

Block Casters he block caster operates on the same general principle as the belt caster: that is, the alu - Tminum slab is formed between upper and lower traveling walls. In place of continuous flat belts, however, the block caster’s traveling walls consist of thick blocks of metal lined up side-by-side so that the exposed surfaces which contact the alu - minum form flat walls about six feet long. The sides of the blocks away from the aluminum are attached to a jointed loop belt, like “caterpillar” vehicle treads.

Block Caster I PREPARATION 3-6

DC INGOT CASTING But most sheet and plate is rolled from thick slabs called “Ingots”, cast by the “direct chill” or DC method. Aluminum is poured into a mold that is only about six inches (150 mm) deep. Progressive cooling while in contact with the mold and bottom block provides a solidified shell around the still-molten core of the ingot . Once this solid shell forms, the bottom block is lowered along with the aluminum shell, while more aluminum is poured in, hardening at the walls and extending the shell. The ingot emerges at about a speed of 1 1/2 to 4 inches per minute (40-100 mm/min.) and is chilled by a water spray to complete its cooling. This direct-chill method permits mold walls only six inches (150 mm) deep to produce a retangular ingot over 30 feet (9 m) long, seven-and-a-half feet (2300 mm) wide and over two-and-a-half feet (760 mm) thick, weighing about 30 tons(27 metric tons). ot metal” (molten aluminum alloy) is Direct-chill ingot casting takes place in a “DC stored before casting in a holding hearth casting pit” and each casting of ingot (s) is called a “at aH temperature ranging from ~1290 to 1345°F “drop ”. Modern casting operations utilize multiple, (~700 – 730°C). Its temperature decreases by commonly 4 – 6, rectangular DC molds typically about 40 to 50°F (22 – 28°C) upon transfer to the 16 to 30" (40 – 75 mm) thick and 45-80" (1.1 – casting pit or station. 2 m) wide. The walls of the mold collar are water cooled to speed the solidification of the ingot shell. The solid shell cools to a temperature in a range of about 570 to 930°F (300 – 500°C) and contracts as it cools, separating from the mold wall before it emerges. The cooling rate is sharply reduced where wall contact is interrupted by this separa - tion, called the shrinkage gap . This effect may permit an unwanted enrichment of alloying elements in a narrow zone near the surface. The enrichment zone is usually removed before rolling, a procedure called “ scalping .” As the bottom block is lowered and the solidify - ing ingot emerges from the mold, the surface is further cooled by water from openings around the inside of the mold. The water is recirculated through cooling towers to maintain a correct temperature for effective ingot cooling. Sensors linked to a computer coordinate the rate of water flow, molten metal levels, the rate of Direct-chill ingot casting (schematic) molten metal addition, and the bottom block speed. Casting speeds may range from one-and-a-half to four inches per minute (37 to 100 mm/min.), I PREPARATION 3-7

Temperature Distribution in an ingot during direct-chill casting. depending on the aluminum alloy and mold size Electromagnetic Casting involved. lectromagnetic casting (EMC ) is a DC ingot Since it is very important to provide a continu - casting variation in which a strong magnetic ous distribution of molten metal, fiberglass socks, fEield confines the molten aluminum while its shell screens and distribution bags are placed in the initially solidifies. Continuous cooling and elimi - ingot head within the confines of the mold. These nation of the liquated zone inherent to the DC provide uniform molten metal distribution and process eliminates the zone of enrichment thus temperature through the entire perimeter of the minimizing the need for scalping . The aluminum mold thus minimizing surfaces defects such as does not contact mold walls, so there is no cold folds or molten metal breakouts. “shrinkage gap ” effect and surface enrichment of At two inches per minute (50 mm/min.), it takes alloying elements is avoided about 2-1/2 hours to cast a 290-inch (7365 mm) Therefore, EMC casting can produce ingots long ingot . An aluminum ingot 24 inches thick, with smoother, metallurgically more homogenous 55 inches wide and 290 inches long (about 2 x 4.5 surfaces that need little or no scalping and/or edge x 24 feet [610 x 1400 x 7365 mm]) weighs about trimming on the hot line. A number of sheet prod - 20 tons (18 metric tons) and contains enough ucts, such as 3xxx and 5xxx beverage stock aluminum, for example, to produce more than alloys , have been cast and rolled without the need 1.5 million beverage can bodies. for scalping DC casting has been used to produce ingots as much as 37 feet (11.25 m) long or longer.

SCALPING To create high qualify surfaces for rolling, the broadest sides of the ingot are shaved by a machine with rotating blades called a “scalper.” Sometimes all four of the sides are scalped.

calping is performed on an ingot to remove any The scalper itself is a specialized milling irregularities or undesirable chemical composi - machine with horizontal blades spanning about five tSions, such as excess oxides or concentrated alloy - feet (1.5 m) or more and rotating on a vertical axle. ing elements, left in its surface by the casting The scalper generally mills the rolling faces of process. By providing smooth, metallurgically the ingot -that is, its widest surfaces, scalping one homogenous surfaces, scalping promotes high side and then turning the ingot over to scalp the quality rolling and avoids the rolling of “slivers” other side. Some operations utilize two sets of into the surface of plate or sheet. cutters permitting simultaneous scalping of both I PREPARATION 3-8

rolling surfaces. Edges and ends which are intermediate trimming. Therefore, based on ingot trimmed during the rolling operation need not be profile, edges may also be scalped, thus eliminat - scalped. Recently, more emphasis is being placed ing the need for intermediate trims or sawing on minimizing downstream operations such as operations.

PREHEATING The scalped ingot must be preheated for hot rolling . The temperature and time is controlled to promote specified ingot properties. There are a variety of methods of preheating ingots. These include “ walking -beam” or “pusher” furnaces, car-bottom furnaces and soaking pits.

Purrehpeoatsinegstheoifngport ebehfoerae thiont grolling serves Pnrgeohtseaaretpinregheamtedeitnhtoemdps erature-controlled several important purposes, including: furnaces. Several variations of preheating proce - P dIure are available to serve different ingot dimen - 1. Raising the alloy’s temperature above the sions or treatment requirements: recrystallization temperature to prevent cold- working ( strain-hardening ) from taking place dur - I Ingots may be stacked up, lying flat and sepa - ing rolling. This avoidance of strain-hardening is rated by spacers, on cars which convey them into the key characteristic which differentiates hot and out of the furnace (“car-bottom” furnace). rolling from cold rolling. I They may be stood on their long edge and 2. Homogenization — that is, putting all soluble pushed through the furnace on a slide (“pusher” alloy constituents into a more complete and uni - furnace) or carried through it by “ walking beams.” form solid solution . During direct-chill casting I They may be inserted, standing on end, into a solidification alloying elements tend to segregate furnace called a soaking pit . inside alloy grains, in low concentrations at grain centers and increasing concentrations toward grain The temperature inside the furnace follows a con - boundaries. This concentric stratification is also trolled cycle which governs the rate of tempera - known as “ coring .” At elevated pre-heating tem - ture increase; the stabilized temperature; the time peratures, these alloying elements redistribute spent at each temperature level; the rate of tem - themselves more uniformly within grains by diffu - perature decrease; and the final temperature at sion, reducing segregation and coring . which the ingot is delivered for rolling. 3. Spheroidizing insoluble constituents. Temperature cycles vary according to alloys and Homogenization pre-heating causes undissolved intended metallurgical results. For example, in precipitates to coalesce into fewer particles and to one case, ingot temperature may be raised directly lose their sharp comers and take on rounder, more to a rolling temperature of perhaps 850°F (455°C) compact shapes which significantly improve the and held at that level right through to ingot deliv - alloy’s formability. ery. In a different case, the temperature might be raised above rolling temperature, held there for a 4. Softening the ingot and thereby minimizing the specified time, and then reduced by the use of mechanical force necessary to reduce its thickness cooling fans to the rolling temperature. by rolling. 5. Relieving stresses in the ingot . Then the hot ingot is laid flat on a conveyor and checked. If its temperature is within the desired range, the carefully engineered ingot is sent to the rolling line. I PREPARATION 3-9

SELF-TEST QUESTIONS 3.8 Name a grain refining element used in SECTION 3: PREPARATION aluminum alloys .

3.1 “Fluxing ” means... a. pouring molten aluminum. 3.9 Grain refiner is added to aluminum b. removing impurities from molten aluminum. alloy… c. mixing in alloying elements. a. in the Hall-Heroult reduction cell. d. cleaning the walls of a reduction cell. b. with the other alloying elements. c. just before ingot casting. 3.2 The main target of fluxing is... d. during solution heat-treating. a. solid impurities. b. water vapor. 3.10 “Continuous casters”… c. dissolved hydrogen gas. a. produce ingots two feet (610 mm) d. undissolved aluminum particles. thick and 24 feet (7.3 m) long. b. operate 24 hours a day. 3.3 The gases usually used for fluxing are... c. produce unbroken slabs or strips. a. hydrogen and chlorine. d. are used to cast large volume parts. b. nitrogen, argon and chlorine. c. oxygen and carbon dioxide. 3.11 A roll caster … d. All of the above. a. produces high-precision work rolls . b. solidifies molten metal between 3.4 In a modern aluminum rolling plant, a chilled rolls. sample of alloy can be sent to the lab c. applies absolutely no hot deformation. and analyzed and the results reported d. None of the above. back to the mill operators within… a. a few seconds. 3.12 The product emerging from belt casters b. a few minutes. or block casters is usually… c. a few hours. a. set aside to cool slowly before rolling. d. a few days. b. used, as-is, in commercial products. c. chilled quickly for immediate cold 3.5 Aluminum alloy which is found to be rolling, “off analysis” is… d. hot-rolled immediately into sheet a. rolled into product more carefully. stock. b. thrown away, c. corrected or recycled. 3.13 In casting, the term DC or Direct Chill d. stored to await a matching customer refers to the fact that… order. a. the molten metal comes in contact with the mold directly. 3.6 If inclusions are not removed from b. there is water circulating inside the molten aluminum alloy before it is cast mold. and rolled, they might... c. water flows over the emerging slab or a. weaken the final product. billet. b. cause streaks or flaws in the product surface. 3.14 In DC casting, the mold… c. damage work roll surfaces. d. None of the above. a. is the size of a finished ingot cross e. All of the above. section. b. consists of two parts, one stationary 3.7 “Final filtration of molten metal is done and one moveable. only when the end user demands mini - c. must be discarded after one use. mal inclusions .” This statement is: d. a and b. a. True. e. b and c. b. False. f. a and c. I PREPARATION 3-10

3.15 “Electromagnetic casting is capable of 3.17 Scalping equipment can be described producing ingots which, for some prod - accurately as… ucts, need no scalping and no hot mill a. a grinder. edge trim.” This statement is: b. a lathe. a. True. c. a vertical or horizontal milling b. False. machine.

3.16 Scalping is applied… 3.18 Pre-heating ingot for hot rolling serves a. to remove the enrichment zone . several purposes. One is to soften the b. to remove surface irregularities. ingot for hot rolling . Another is… c. to obtain uniform slab thickness. a. to oxidize the surface. d. a and b b. to homogenize the alloy. e. a and c c. to anneal the metal. f. a, b and c. Rolling Aluminum: From the Mine through the Mill 4 THE ROLLING MILL DESCRIPTION AND FEATURES The rolling process must produce plate or sheet with not only accurate dimensions, but such other attributes as: flatness , edge quality and correct thickness profile; specified physical properties; and freedom from surface defects. So, before we follow an ingot down the rolling line, let’s take a look at the rolling mill itself. The most basic parts of a rolling mill are two motor-driven cylinders called “ work rolls .” These rotating rolls draw aluminum through, and reduce its thickness to the width of the gap between them. The gap is variable. A thick ingot can be reduced to thin sheet either by passing it repeatedly between the same work rolls and narrowing the gap each time, or by passing it through a series of rolls with progressively smaller gaps. I The work rolls , which actually contact and shape Gap adjustment machinery , to set the gap the aluminum, lie at the heart of a massive assem - between work rolls accurately and then to main - bly of scientifically designed and precision manu - tain it against the resistance of the alloy undergo - factured parts that make up a modem rolling mill. ing thickness reduct1on. I The mill’s main mechanical components also Coolant systems , to apply liquid include: coolant /lubricant to the rolls. I The mill stand : the strong structure which And, for sheet mills, coil and core handling supports various parts and withstands the enor mous machinery to install, remove and transport heavy tensions imposed by rolling. coils of rolled sheet. I Back-up rolls , whose function is to support The components which directly apply the mechan - the work rolls against excessive flexing and ical force that reduces the aluminum thickness vibration. must be both strong and precise, capable of apply - ing forces up to millions of pounds with uniform I , which provide the power that Drive motors accuracy of a few hundredths or thousandths of turns work rolls and forces aluminum through the an inch. roll gap . Rolls with appropriate diameters and surfaces I , which convert the rotation rates Gearboxes must be used. Automatic roll -changing machinery of the motors into the appropriate rotation rates makes it relatively easy to adapt a mill to chang - and torque (turning force) for the work rolls . ing product requirements. I , which transmit the turning Drive spindles No less important than the large mechanical com - force of the motors to the work rolls . ponents are the control systems, which sense I product thickness and shape, and the computers Roll bending machinery , capable of induc - ing slight, controlled flexing in the rolls to com - which analyze the data and control the mill’s pensate for thermal expansion or other distortion adjustment systems to maintain product tolerances and, thereby, control product flatness . while the mill is running. I THE ROLLING MILL 4-2

A number of rolling mill parameters are con - At many mills today, the operator may preset trolled, either by the operator or by computer . such parameters and then let the computer auto - They may include: roll gap , roll force, roll torque, matically run the mill through the prescribed roll cooling, roll bending, roll tilting and sheet process. tensions.

Main features of a four-high rolling mill. I THE ROLLING MILL 4-3

SINGLE-STAND AND TANDEM MILLS A mill with one set of work rolls is a “single-stand” rolling mill; several sets of work rolls in a coordinated series form a “multiple-stand” or “tandem” mill.

MILL ROLLS The hard steel rolls are precision-engineered. Depending on the product, roll surface may range from a dull “ mill finish ” to mirror bright. Roll diameter must not vary from specifications by more than two and a half ten-thousandths of an inch. To compensate for flexing and heat distortion, a work roll may be crowned or concaved — the roll being thicker or thinner by a few thousandths of an inch around the middle than at the ends.

mill roll is basically just a long smooth steel Because of such considerations, it is economi - cylinder with an axle shaped to be gripped cally important to use rolls with surfaces appropri - aAnd rotated by powerful motors. The apparent ate to the type of product to be produced. A cus - simplicity of its shape masks a lot of complex tomer who would be satisfied with mill finish alu - engineering. minum might be just as satisfied with a smooth It must be a near-perfect cylinder with a smooth finish. The unnecessarily smooth rolls, however, but hard surface. It must also be stiff enough not might impose equally unnecessary penalties on to bend excessively with the high force needed to the mill operation. flatten an ingot or plate of aluminum alloy. It is also important to maintain work roll surface The aluminum product receives its specified quality in service. On hot work rolls , even the surface directly from contact with the work rolls , smallest blemishes must be avoided, to prevent which must therefore have the intended type of aluminum from sticking locally and creating sur - surface. Roll surface finish is also very important face flaws in the rolled product. Hot work rolls both for rolling efficiency and for product quality. often pick up tiny amounts of aluminum oxide or Depending on specifications, flat rolled aluminum even aluminum metal, a phenomenon known as may be produced with a relatively rough “ mill fin - “roll coating.” Within limits, this can be advanta - ish ” surface, or with smoother surfaces up to and geous because it tends to increase friction and including “bright sheet” with a mirror-smoothness. make the rolls more efficient. Care must be taken At the same time, the roll ’s degree of roughness to avoid excessive build-up, which can result in largely determines how effectively it can “ bite ” product surface flaws through imprinting or oxide into the aluminum and, by friction, force it through detachment. the roll gap . A rougher roll applies more friction Work roll surface quality is closely monitored and a stronger bite than a smoother roll , so the for excessive wear, deterioration or damage, to rougher roll can apply greater thickness reduction assure high quality products. Chrome plating of per pass — an important factor in mill efficiency. the work rolls was adopted to improve surface In order to provide sufficient friction with a hardness , improve surface finish and extend the smooth roll surface, it may be necessary to reduce life of the work rolls . the application of coolant /lubricant. This, in turn, Rolling solution, roll coolants or oil emulsions reduces the rate of heat removal and necessitates is another closely controlled parameter. Computer compensating changes in the rolling plan. controls provide optimum addition of the coolant I THE ROLLING MILL 4-4

to the work rolls . Controlled application of only for specific rolling regimes with appropriate coolant improves control of the work roll temper - alloys and thickness reductions. It will not have ature, thus improving shape control and ultimately exactly the right shape for other rolling tasks. yielding a flatter plate or sheet. Moreover, it will fail to compensate or can even In addition, roll design is intimately connected distort the product, if roll deflection is allowed to with total mill design, because important trade-offs become greater or smaller than intended. occur when roll size and properties are varied. Alternatively, in some circumstances work rolls Roll diameter and roll stiffness are two of the may be “concaved” — made slightly smaller in most important factors. Other things being equal, diameter at the center than at the ends — to com - a mill’s efficiency in reducing product thickness pensate for anticipated thermal expansion which depends on work roll diameter. Product flatness would otherwise cause undesired crowning. depends largely on roll stiffness which, in turn, Smaller-diameter rolls are also more vulnerable depends on both the diameter of the roll and the to horizontal deflection in the pass-through direc - steel from which it is made. tion. The friction of the aluminum passing Work rolls with a relatively small diameter can between rolls tends to drag them in the same reduce aluminum thickness by a greater propor - direction and may cause a roll to deflect until its tion in one pass than rolls with a larger diameter. elasticity overcomes the friction and snaps it On the other hand, smaller-diameter rolls bend straight again. Such deflections must be prevented more easily than those with larger diameters, mak - by appropriate choice of roll size, and/or provision ing it harder to maintain uniform, accurate product of horizontally stabilizing back-up rolls. flatness . Overall roll flexibility increases with Because of their larger mass, larger work rolls length. The wider the rolled product must be, the can absorb or surrender a given amount of heat longer the roll must be and the more the roll is with less overall change in temperature than likely to deflect without support. smaller ones. Thus larger-diameter rolls have Roll deflection can be counteracted to some greater thermal stability. extent by “crowning" the roll : i.e., making it Larger, more massive work rolls also have more slightly larger in diameter by a few thousandths of physical inertia — more resistance to changes of an inch (tenths of a millimeter) at the middle than motion. Therefore, it takes more energy to accel - at the ends. Because crowning is a fixed dimen - erate and decelerate their rotation, a consideration sion, it can compensate accurately only for a that may substantially affect mill design and eco - matching, fixed amount of roll deflection. This nomics, especially for reversing mills and other implies that any one crowned roll is fully suitable start-stop rolling mills.

ROLL CONFIGURATIONS But most aluminum plate and sheet rolling requires so much force that it is difficult to avoid excessive flexing with only the two work rolls . So each work roll is backed up by a larger roll , pressing against it to keep it straight. Rolls are positioned one above the other. A stand with two rolls is called a “two-high” mill. A stand with two work rolls plus two back-up rolls is called a “four-high.” Some two-highs are used, mostly to roll foil or in laboratories. And mills with three-, five- or six- roll combinations are also operated. But the four-high mill is the most widely used for rolling aluminum. Some mills are designed to roll in only one direction; others, called “reversing mills” can roll aluminum back and forth. I THE ROLLING MILL 4-5

Common roll configurations: a) two-high, b) four high, c) cluster. I THE ROLLING MILL 4-6

n principle, it takes only two work rolls to tion is always its ability to control work roll reduce aluminum to any desired thickness. deflection. In commercial practice, however, work rolls are Backup rolls are also applied in other configura - usually supported by “back-up rolls” that press tions to combat horizontal work roll deflection as against the work rolls and turn with them but well as vertical deflection. This is accomplished never touch the product. Either the work roll or by positioning the back-up rolls off the vertical the back-up roll may be driven directly by the axis of the work roll stack, so that their force mill's motors. The other roll becomes an idler, against the work rolls is directed both vertically turned by the friction of the driven roll . and horizontally. The most common arrangement is the “four- Configurations using multiple back-up rolls are high” mill in which the two work rolls are placed generally termed “cluster mills” and are usually one above the other and each is supported by a used to roll thin products. backup roll , above the top work roll and below the The combination of work rolls and back-up rolls bottom one, in a vertically stacked configuration in forceful contact with each other introduces the “four (rolls) high.” possibility that the very small variations from per - In this configuration, the chief purpose of the fect roundness which would be acceptable in backup rolls is to maintain accurate, uniform either roll alone could add up to an unacceptable product flatness by preventing excessive vertical deviation for the entire stack. In addition, small deflection in the work rolls . Thus, the main acceptable amounts of “give” in the bearings requirement of a back-up roll is strength , achieved which support each roll can also add up to unac - by sufficient diameter to withstand the “separating ceptable deviations from perfect rotation as more force” applied by the aluminum’s resistance to rolls (and more bearings) are involved. deformation. So roll grinding and roll bearings must be pre - A larger-diameter back-up roll can permit the cise enough to keep the “eccentricity” (off center use of a smaller-diameter work roll and, at the deviations) of the entire roll stack, as a unit, with - same time, increase the thermal stability of the in the limits required for accurate, smooth product unit by acting as a heat sink or source for the thickness. work roll . However, a more massive backup roll Roll diameters must be accurate to within 2.5 also increases the inertia of the rolling mill and ten-thousandths of an inch (0.006 mm). Total roll - demands more energy for acceleration and decel - stack eccentricity may be held within limits as eration. small as 4 ten-thousandths of an inch (0.01 mm) Thermal stability and inertia may influence or less. backup roll selection, but the dominant considera -

HOT OR COLD ROLLING Rolling is done either “hot”— with hot, softened aluminum — or “cold”, with aluminum at room temperature. n aluminum rolling terms, “hot” and “cold” have It takes more energy, of course, to roll cold more technical definitions than their common metal than metal which is softened by a high mIeaning. “Hot” rolling means rolling at a metal enough temperature. Cold rolling can provide a temperature high enough to avoid strain-hardening smoother final surface and different tempers than (work-hardening) as the metal is deformed. hot rolling . The thinnest products must be cold “Cold” rolling means rolling the metal at a tem - rolled to their final thickness. perature low enough for strain-hardening to occur, Hot mills currently roll sheet at rates approaching even if the alloy would feel hot to human senses. 2,000 feet per minute (600 m/min). In practice, hot-rolling temperatures may Cold mills can roll sheet at rates up to 7,000 decline enough during rolling to permit some feet per minute (2135 m/min) or more. strain-hardening to occur. I THE ROLLING MILL 4-7

these “ glide planes ”; such “slip lines” are some - Hot Rolling – Metallurgical Effects ot rolling has at least two significant metallur - times visible on the metal surface. The lattice gical effects: planes are never ideal. There are breaks and off - H sets in them, called “dislocations”, which tend to 1. It welds pores left by casting, creating a denser, block slippage and so resist deformation. stronger metal. Rolling, or other cold deformation, tends to break 2. It breaks up and distributes hard constituents and offset the lattice planes, thereby increasing the of iron and silicon which have formed at grain number of dislocations which resist force and boundaries. This action transforms brittle cast making the metal stronger and harder. This effect alloy into ductile wrought alloy, because frag - is deliberately induced as “~ hardening” ( work mented and distributed constituents offer less hardening ) to strengthen aluminum alloy products. resistance to the internal metal flow necessary to Various applications of strain hardening are ductility . Reduction schedule or reduction per pass included in the “H-tempers” and some of the and directionality of rolling has a very important “T-tempers” of aluminum. impact on some of the damage characteristics of the high strength aircraft alloys . The same hardening effect can occur prematurely, before rolling is completed; it is undesirable if a soft product is ordered. In such cases, annealing is Rolling temperature also influences the appear - performed to undo the work hardening that has ance and structure of the final product. Lower hot- occurred. rolling temperatures yield relatively brighter prod - uct surfaces and elongated alloy grains, while Work hardening has a natural limit for each alloy because it is, in fact, straining the alloy toward its higher hot-rolling temperatures can induce recrys - strength limit. The number of dislocations which a tallization in the metal. The rolling temperature is crystal lattice can develop is limited and, there fore, selected according to the product properties that so is its maximum strength . As work hardening are to be achieved. increases, the metal can withstand increasing force Too high a temperature can weaken grain without breaking; but it retains less reserve boundaries and cause boundary cracking. against additional force. Consequently, rolling temperature is kept 20 to 90°F (10 to 50°C) below a certain limit — the Metal cold worked to its maximum limit can be “solidus” or solidification temperature — of each broken by only a slight additional deformation. alloy. Thus, cold working, or strain-hardening , is applied to the degree required by product specifications Cold Rolling – Metallurgical Effects which involves a trade-off between maximum n the atomic level, solid metals have a “crys - strength and maximum ductility . tal lattice ” structure: its atoms are arranged iOn a regular pattern which can be considered, The heat of annealing relieves the distorted, dislo - ideally, as a stack of flat planes. cated lattice structure and allows it to reform in relatively undislocated planes again, restoring When the metal is deformed, as it is in flat rolling, ductility at the cost of the acquired strength . regions of the crystal “slip” past each other along I THE ROLLING MILL 4-8

NOTES I THE ROLLING MILL 4-9

SELF-TEST QUESTIONS 4.8 “Hot rolling ” means rolling aluminum... a. when it is too hot to touch bare- SECTION 4: ROLLING MILL handed. b. with pre-heated work rolls . 4.1 The parts of a rolling mill that apply c. hot enough to avoid strain-hardening . thickness reductions by direct contact d. hot enough to induce full annealing . with the product are called… a. the mill stand . 4.9 Which, if any, of the following are signifi - b. the drive spindles . cant effects of hot rolling : c. the work rolls . a. making the metal smoother. d. the backup rolls. b. making the metal more dense. e. the gap adjustment machinery. c. making the metal more ductile. d. making the metal more weldable. 4.2 “The purpose of backup rolls is to permit e. none of the above. the use of smaller-diameter work rolls .” This statement is: 4.10 “Cold rolling” means rolling aluminum... a. true. a. at or near room temperature. b. false. b. after refrigeration. c. at any temperature which avoids 4.3 What type of work roll surface can be strain hardening. used efficiently for all rolled products and specifications? 4.11 In general, cold deformation of alu - a. mirror-smooth. minum... b. smooth. a. increases its strength . c. mill finish . b. decreases its strength . d. extra rough. c. does not affect its strength . e. none of the above. d. changes its strength unpredictably. e. causes it to break immediately. 4.4 Which of the following factors affect the amount of roll deflection during rolling? 4.12 Cold deformation of aluminum is effec - a. roll width. tive because... b. roll diameter. a. it twists the shape of the crystal c. product width. lattice . d. product ductility . b. it makes lattice planes slip past each e. amount of applied thickness other. reduction. c. it breaks and offsets lattice planes. f. all of the above. d. it rearranges alloying elements in the lattice . 4.5 The most common roll -configuration for rolling aluminum is the... 4.13 In general, as strain-hardening increas - a. two-high. es, a metal’s ductility ... b. four-high. a. increases. b. stays the same. 4.6 Which of the following affects the roll c. becomes unstable. gap ? d. decreases. a. roll crown. b. roll bending. 4.14 The amount of strain-hardening that can c. coolant /lubricant sprays. be achieved in aluminum alloy... d. all of the above. a. is the same for all alloys . b. is unlimited. 4.7 Roll bending is the equivalent of... c. has a natural limit depending on the a. smoother finish. alloy. b. changing the roll crown. d. has a limit depending on product c. more reduction. thickness.

Rolling Aluminum: From the Mine through the Mill 5 SHEET ROLLING OPERATIONS Now let’s follow that preheated ingot through the rolling and finishing processes that convert it into a coil of thin sheet. The first stage is the “ breakdown mill ,” a massive single- stand, four-high, reversing, hot-rolling mill.

he first rolling mill encountered by an alu - the work rolls . A typical breakdown mill may minum ingot entering the rolling line is called apply 5,000 horsepower (3730 kilowatts) to each Tthe “ breakdown mill .” It is usually a single-stand work roll , for a total of 10,000 working horsepow - four-high reversing hot rolling mill. er (7460 kilowatts) to drive the ingot through the Its main function is to “break down” the ingot , gap, where it undergoes a compression force of reducing its thickness to the dimensions of plate. about 8 million pounds (3,635 metric tons) along For some purposes the breakdown mill alone the contact line. can produce final product thickness. For others, Breakdown mills are often described by the the product of the breakdown mill is fed through length of the work rolls they can accommodate additional rolling mills (hot or cold) for further (and consequently the maximum width of product thickness reduction and/or surface finishing. they can roll ): for example, a “120-inch mill” In a breakdown mill , the work rolls are powered (“3-meter mill”) or a “168-inch mill” (“4.25-meter and their back-up rolls are turned by contact with mill”).

BREAKDOWN MILL PARAMETERS Its operator, in an elevated control room called the pulpit, raises the upper rolls from their last setting and sets the gap for the first pass — perhaps two or three inches (50-75mm) less than the ingot thickness. ince it must reduce an ingot as much as 30 inches thick (760 mm), the typical breakdown mSill is a large, powerful assembly. Its lower work roll and back-up roll are fixed in position. Its upper work roll and back-up roll are raised or lowered by screw-threaded or hydraulic mount - ings in the mill stand ’s side columns, so the opera - tor can continuously vary the gap between the working rolls. As indicated previously, the roll gap for each pass is only one of several mill parameters that are set to achieve the desired product properties. Rolls with appropriate diameters and surfaces must be in place. Roll acceleration and speed are controlled as required for the alloy and the intend - ed reduction. In many modern mills the entire rolling sequence is computer -controlled, once the An aluminum-rolling mill operator in the control pulpit. operator feeds in appropriate instructions. I SHEET ROLLING OPERATIONS 5-2

BREAKDOWN COOLANT /LUBRICANT APPLICATION He also sets an appropriate pattern for applying liquid coolant . It may seem odd to preheat an ingot to the right temperature, and then apply coolant when you roll it, but there are two good reasons for doing this. The coolant doubles as a lubricant to prevent aluminum from sticking to the rolls And the ingot undergoes both friction and a compression force of about 4,000 tons as the rolls reduce its thickness. Those forces generate extra heat which must be carried away to maintain a correct temperature. As we mentioned earlier, heating, cooling and reshaping all contribute to the final temper of rolled aluminum, and those factors are carefully controlled throughout the process.

prepared ingot is sent into the mill at a care - Both of these functions — heat removal and fully adjusted rolling temperature. The rolling lubrication — are performed in a breakdown mill pArocess itself generate s additional heat: from fric - by application of a single liquid coolant /lubricant, tion between the ingot and the work rolls ; and typically an emulsion of water with about five from the severe deformation of the metal — in percent oil which is continuously filtered and effect, internal friction — as its thickness is recirculated. reduced. Other types of rolling mills may use different This additional heat must be removed to main - coola nt /lubricant formulations suited to their tain temperature control. This is necessary not only functions and products. to prevent excessive thermal distor - tion of the mill rolls but also to con - trol alloy temper throughout the rolling sequence. In addition, the work rolls must be lubricated, to prevent the hot alu - minum from sticking to the rolls and causing surface flaws on the product. Both the quantity and application pat - tern of lubrication must be appropri - ately controlled. Therefore, a system of hoses feeds liquid coolant /lubricant through the nozzles of spray bars installed in front of the rolls. Lubricant is generally suppressed when the ingot enters the workroll gap, to promote a good friction “ bite ” by the rolls, and then is applied while the ingot passes through. There must be enough lubricant to prevent stick - ing but not too much. Either too little or too much lubricant can impair the product surface. A rolling mill coolant /lubricant system (schematic drawing). I SHEET ROLLING OPERATIONS 5-3

BREAKDOWN ROLLING Once the breakdown mill is “set up”, the operator manip- ulates th e table rolls — two sets of rollers independently controlled — to position the ingot and start it between the work rolls . Cross rolling is sometimes needed to achieve a specific width. The work rolls draw the ingot through and reduce its thickness. Then the operator narrows the gap a few more inches (centi- meters), reverses the mill, and sends the ingot back through it. The ingot is rolled back and forth until if becomes a long slab , four to five inches (100-125 mm) thick.

he ingot is positioned and fed to the work rolls and is reduced to perhaps 11 inches (280 mm). by a set of conveyor rollers in the “feed table” The gap is repeatedly narrowed for each pass until Tdivided into right and left segments ( table rolls ) the desired breakdown thickness is reached. which are independently powered and controlled. The operator in the control pulpit may read the By matching or varying the right and left convey - roll separation directly from a digital display or speeds, the mill operator can maintain ingot inside his booth, or he may monitor the roll gap alignment or turn the ingot to reposition it. Thus, settings from a large dial or indicator atop the ingot can be “cross-rolled”, i.e., run through the mill. In some modern mills the rolling sequences work rolls “sideways”, instead of in its normal are controlled automatically with sensors provid - lengthwise orientation, to roll it into a product ing feedback to the rolling program while the wider than the original ingot . operator monitors the operation. The table rolls push the ingot into contact with When the ingot is rolled in its usual lengthwise the work rolls , but it is the work rolls themselves position, the reduction in its thickness is compen - that “ bite ” the ingot by friction and force it sated almost entirely by a corresponding increase through their gap. in its length. Friction along the line of contact The ingot is reduced in a number of passes to a between the work rolls and the ingot is generally slab a few inches (centimeters) thick. For exam - enough to prevent the ingot from widening signif - ple, a 15-inch-thick (380 mm) ingot may be icantly. reduced to about 13 inches (330 mm) on the first The edges of the ingot may also be rolled by work pass. Then the roll gap is reset, the direction is rolls on vertical axles at one end of the roll tables, to reversed, and the ingot is passed through again prevent edge cracking and control width spread.

INTERMEDIATE HOT ROLLING If it is to be made into sheet, it is usually conveyed to another single-stand hot mill and is rolled down to a plate thickness of about one inch (25 mm).

ome rolling mills apply intermediate hot transfer plate-thickness slabs directly from the Srolling , but most of the newer rolling mills breakdown mill to a tandem sheet-rolling mill. I SHEET ROLLING OPERATIONS 5-4

and forth through the reversing mill . Once the SHEET HOT ROLLING : THE SINGLE strip is rolled to the desired thickness, generally STAND REVERSING MILL ome mills utilize a single stand reversing hot less than .500” (12 mm), the metal can then be mill. This type of hot mill also includes one or coiled. The mill has rewind capabilities on both tSwo coilers, one on each side of the mill. Starting sides, and the slab is generally coiled one or three with a standard size ingot , the metal is rolled back times before the rolling is completed.

SHEET HOT ROLLING : THE TANDEM MILL The plate is rolled down to sheet thickness in a tandem, or multiple-stand, hot-rolling mill. There, several thickness reductions take place simultaneously as the sheet passes between several sets of work rolls with smaller and smaller gaps. The stands of a tandem mill must be closely coordinated. From each stand, the sheet emerges thinner and longer — and so, faster — than it went in. Multiple-stand rolling speeds must be coordinated to accommodate sheet acceleration. In fact, some sets of rolls must have a little extra power and speed, to keep just the right amount of tension on the sheet. Too little tension would let the sheet buckle; too much would tear it. A modern multi-stand hot-rolling mill is computer -controlled to meet batch specifications. Sensors automatically measure sheet tensions, roll speeds and roll power relationships, and the computer adjusts them. n a multiple-stand mill, roll power relationships, essentially unchanged, any reduction in thickness roll gaps and sheet tension are all interrelated must be compensated by a proportional lengthen - Iand must be coordinated. ing to maintain constant volume. For example, if a When plate or sheet is reduced in thickness, the plate 1.2 inches (30 mm) thick is rolled down to total volume of metal, of course, remains the same sheet 0.2 inch (5 mm) thick, it is reduced in thick - but is redistributed. Since the width of the piece is ness by a factor of six. This product emerges from the rolls six times longer and, there - fore, six times faster than it entered. This principle applies to each stand in a tandem mill . Since each stand except the last feeds its output into the next stand, the roll speeds must be progressively higher from stand to stand,

A four-stand tandem rolling mill with take-up coil (schematic drawing). I SHEET ROLLING OPERATIONS 5-5

adjusted to maintain correct sheet tension. Since gap changes are rela - tively slow, tension is controlled more quickly by adjusting roll speed. Tension-measuring devices are located between the stands of a tan - dem mill . The rolled sheet passes over each device at a slight angle, generating a downward force which is measured by load-cells in the bear - ing supports. An automatic feedback system adjusts roll speeds and gaps as necessary to maintain correct sheet tension. A tandem aluminum-rolling mill. Proper composition and application to accommodate the accelerating sheet. Each of coolant /lubricant is also crucial to tandem mill speed increase must be large enough to keep ten - sheet-rolling to remove excess heat; avoid dulling sion on the sheet and prevent buckling, but not the product surface or causing undesirable reduc - large enough to tear the sheet. tion marks or “herringbone” and prevent alu - Furthermore, the larger the reduction of thick - minum from sticking to work rolls . Mill lubricants ness imposed by any single stand, the more turn - may include various additives which increase their ing power it requires. Power differentials between load-bearing capacity — their ability to prevent stands also affect sheet tension, so roll speeds and direct contact between the aluminum and the steel turning power must be coordinated. even under high pressures. The roll gap is another influence which can be Also, the coolant /lubricant formulation must remain chemically stable under rolling conditions.

COILING AND EDGE TRIMMING As sheet emerges from the hot mill, it is rolled up into a coil which may be as much as 8 feet (2.4 m) in diameter.

fter rolling, this sheet is edge-trimmed on its way to coiling . AA tension reel wraps the emerging sheet into a tight coil, typically with an inside diameter of about 20 or 24 inches (500-600 mm) and an out - side diameter in excess of 90 inches (2285 mm). Sometimes the ends of the sheet are secured by welding at the inside and outside of the coil. Otherwise, the coil is wrapped with a confining band. The mandrel on which the coil is wound contracts for removal of a full reel.

Coils of rolled aluminum awaiting further processing (right). I SHEET ROLLING OPERATIONS 5-6

ANNEALING If additional rolling is needed, it may be done at room tem - perature in single- or multiple-stand cold rolling mills. They operate on the same basic principles as hot rolling mills. Before, after, or between cold rolling operations, the sheet may be fully or partially annealed for various reasons by heating and slow cooling, to soften it and counteract the tempering that has already taken place. Applied before or between cold rolling operations, annealing prepares the metal for rolling. Partial annealing may be applied after rolling is completed, to stabilize some tempered properties. Full or partial annealing may be used to prepare the sheet for later mechanical forming in product fabrication. Or the annealed condition may simply be the final temper requested by the customer.

Purposes of Annealing Full Annealing luminum alloys may be hardened by hot or ull annealing heats the alloy hot enough, long cold rolling procedures to a degree that is not enough, to soften the product completely — dAesired in the finished product or that would inter - tFhat is, to achieve full recrystallization. fere with further rolling and the achievement of a “Recrystallization temperature ” is not a precise desired temper . term. Recrystallization does not occur suddenly at Heat-treatable alloys may be sufficiently heated a sharply defined temperature; instead, it begins and cooled during hot-rolling to undergo some gradually as the temperature rises into an effective partial solution heat treatment and precipitation range, and it progresses to completion over an hardening . extended time. The effective recrystallization tem - Cold rolling, on the other hand, elongates grains perature depends on the alloy and on the deforma - and sets up internal stresses and strain. These tion and treatment it has previously undergone, as changes create resistance to further deformation: well as the annealing “soak ” time. the cold-rolled plate or sheet is said to become Full annealing converts both heat-treatable and “work-hardened.” non-heat-treatable wrought alloys into their soft - Unwanted precipitation hardening or work hard - est, most ductile, most workable condition, desig - ening is removed before further rolling or product nated as the “O- temper .” finishing by annealing — that is, by heating the For full annealing of heat treatable wrought alu - aluminum alloy above its recrystallization temper - minum alloys , the metal is typically “soaked” for ature and holding it there long enough for the about two hours at a temperature in the range of grain structures created earlier to re-crystallize 635 to 700ºF (335-370ºC) to remove cold work, and relieve the internal stresses. or 750 to 800ºF (400-425ºC) to counteract heat Annealing can be applied at any stage in the treatment. rolling process. Then the metal is cooled slowly, at a closely controlled rate appropriate to the alloy. This per - I SHEET ROLLING OPERATIONS 5-7

mits maximum coalescence of precipitating parti - Annealing Methods cles, minimizing hardness . nnealing applies heat by convection through Non- heat-treatable alloys are annealed by heat - the atmosphere inside an annealing furnace. ing for one-half hour to two hours (most often TAo avoid oxidizing any unevaporated lubricant about one hour) at a temperature in the range of residues or forming magnesium oxide on magne - 635 to 765ºF (335-405ºC). Then they are cooled at sium-bearing alloys , annealing may be carried out a controlled rate. in a dry, inert (low-oxygen) atmosphere such as Annealing also provides the conditions for nitrogen gas. A large integrated aluminum rolling stress-relief and may even be applied specifically plant may have its own nitrogen generating plant for that purpose if furnace schedules and product for this purpose. requirements permit. Annealing methods may be divided broadly into The “H1” and “H3” aluminum alloy tempers are two general approaches: batch annealing and sheet created by applying specific amounts of strain- annealing . hardening to fully-annealed metal. These are called “ rolled-to- temper ” products. Batch Annealing /Treatment atch annealing means loading a furnace with a Partial Annealing batch of metal, usually coiled sheet, and hold - s its name suggests, partial annealing stops iBng it there until the annealing process is com - short of full annealing and, instead, applies plete. Coils of aluminum sheet are annealed as a pAatterns of temperature and time to strain-hard - single batch, depending on the size of the coils ened, non-heat-treatable wrought alloys in order to and the size and shape of the furnace. develop properties in between fully soft and fully In batch annealing , heat conveyed by the fur - work hardened. It is typically performed after the nace atmosphere to the outside surfaces of the completion of cold rolling. coils must be conducted through the metal to the These intermediate tempers are formally desig - innermost layers, and sufficient time must be nated as “H2X tempers”: strain-hardened and par - allowed for all parts of each coil to absorb enough tially annealed. heat to achieve the planned anneal. A quality partially-annealed product requires Batch annealing is an efficient approach and is sophisticated process control . the most commonly used method in high-produc - tion sheet mills. Stabilization Annealing ertain non-heat-treatable aluminum-magne - Sheet Annealing /Treatment sium alloys , such as 5052, 5456, 5083 and n sheet annealing , uncoiled sheet is passed 5C086 and also alloy 3004 develop high strengths through a furnace so that its entire surface con - because of their high internal stresses after rolling. tIacts and is heated by the hot furnace atmosphere. However, because of a tendency for magnesium to This heats the sheet rapidly, permitting the devel - come out of solid solution , the initial temper of opment of a finer alloy grain structure. these alloys is unstable and they may suffer “ age- Uncoiled sheet may be annealed either as con - softening ” — a gradual loss of some strength over tinuous sheet passed through the furnace from coil time, at room temperature. Such alloys may also to coil or as cut sheet transported through by a undergo dimensional changes, unless stabilized. conveyor. Further age-softening is prevented and the mechanical and dimensional properties of these alloys are stabilized by heating them to a relative - ly low temperature, usually about 350ºF (180ºC). After stabilization, the strength , hardness and dimensions do not change at room temperature. I SHEET ROLLING OPERATIONS 5-8

COLD ROLLING Cold rolling is used to give aluminum sheet a desired strength and temper ; or to provide a final surface finish; or to reduce sheet to very small thicknesses. For example, aluminum beverage can stock is cold-rolled from sheet about one-tenth of an inch (2.5 mm) thick down to about one-hundredth of an inch (.25 mm). This may be done in four or five passes through a single-stand mill or in one pass through a multiple-stand mill. luminum alloys can be cold rolled down to stand cold rolling. The tandem mill applies several thicknesses of around 0.002 inch (0.05 mm). thickness reductions in a single pass and readily APure (low-alloy) aluminum can be cold rolled into matches or surpasses the productivity of the foil as thin as 0.0001 inch (0.0025 mm). single-stand. The first pass through a single-stand cold rolling Lubricants used for cold rolling are usually mill may reduce the material thickness by about composed of a load bearing additive in a light 50 percent. Subsequent passes may reduce the petroleum distillate oil. Lower-viscosity oils trans - thickness by similar or smaller amounts. fer heat more efficiently and improve rolling per - Sheet destined for cold rolling to thicknesses formance. A lower limit on viscosity is imposed under about 0.040 inch (1 mm) is usually hot by oil evaporation, flash and fire points at rolling rolled to about 0.120 to 0.240 inch (3-6 mm) temperatures. Oil-water emulsions have been before cold rolling begins. developed for high speed cold rolling and have As the work hardening increases, it takes more been adopted at some mills. Rolling lubricants power to roll the sheet thinner. Beyond a certain are filtered to remove rolling wear debris, then degree of hardness , the metal may crack if it is recirculated. rolled again. This imposes practical limits on the The length of sheet wrapped in a single coil amount of cold rolled thickness reduction that can depends on the coil’s diameter and on the sheet be achieved in an uninterrupted series of passes. thickness. The 38 inches (965 mm) distance When further thickness reduction is necessary, the between an inner radius of 10 inches (255 mm) sheet must be annealed as described above to soft - and an outer radius of 48 inches (1220 mm) en the metal for further cold rolling. (20-96-inch [510-2440 mm] coil diameters), can The degree of cold rolling performed after accommodate 760 1ayers of sheet rolled to a typi - (or without) annealing is calculated to produce cal thickness of 0.05 inch (1.25 mm). One such desired properties in the rolled sheet: either its coil could hold a strip of aluminum sheet over two final temper or the condition required to achieve miles (3.25 kilometers) long which started from its final temper . 24 inch thick by 24-foot long (610 x 7315 mm) To produce a reflective surface on cold rolled ingot . sheet, smaller thickness reductions are rolled dur - (Flat-rolled metal more than one-quarter inch ing the final passes. The brightest surfaces are [6.3 mm] thick is not usually coiled but is deliv - produced by the use of highly polished work rolls . ered to a run-out table and is cut to specified A typical single-stand cold mill can roll sheet at lengths.) a rate of about 5,000 to 6,000 feet per minute (1525 to 1830 m/min) on each pass. Gauge and Profile Control Although the sheet enters the mill “cold”, at s technology has progressed, the requirements room temperature, the friction and pressure of placed on flat-rolled aluminum products for rolling may raise its temperature to about 180ºF aAccuracy of thickness (gauge), flatness and cross- (80ºC) or more. This excess heat must be removed sectional shape have become more demanding, by an appropriate coolant /lubricant. and rolling technology has advanced to keep pace. Cold rolling in a tandem (multiple-stand) mill is Initially, rolling technology concentrated mainly governed by the same general principles as single- on achieving uniform thickness throughout the I SHEET ROLLING OPERATIONS 5-9

length of the rolled product. In recent years, it has mill to make appropriate corrections while the added a more sophisticated ability to control rolling continues. Such measurement/control feed - transverse (cross-width) thickness. back loops make it possible to produce sheet and The cross-width thickness variation is called plate with more accurate profiles than ever before. profile, and it can be controlled during the hot In some cases, feedback loops may be augment - rolling process. Profile can be further described ed by “feed-forward” loops in which the product as having two main components, namely crown is measured both approaching and leaving the and wedge. work rolls , and the two measurements can signal For most alloys , the edges of the sheet will be automatic mill adjustments in time to correct the slightly thinner than the center (positive crown), rolling of the product as it enters the work rolls . as a result of slight bending or bowing of the Product thickness (gauge) may be measured work rolls as they work to reduce the slab thick - during rolling by contact rolls or by non-contact ness. The higher the rolling load, the greater the sensing of X-rays or other radiation beamed degree of bending of the work rolls , and the high - through the metal. er the crown. More dilute alloys (softer) are some - Surface flatness may be measured by segmented times prone to having thicker edges than center, contact rolls or by laser beams. or negative crown, a condition which can have an Instantaneous thickness corrections during adverse effect on flatness during subsequent cold rolling may be made by activating hydraulic rolling passes. pistons which move the rolls slightly upward Wedge is the difference in the thicknesses of the or downward to adjust the roll gap as needed. two edges where the sheet increases in thickness Thickness and profile considerations overlap across the strip , and can be caused either by work when the separating force applied by the rolled rolls that are not parallel or by an uneven temper - product causes work rolls to deflect. A variety of ature distribution across the roll gap . techniques (called “actuators”) are available to Many applications of sheet and plate require the control gauge and/or profile during rolling. They flattest possible cross-sectional profile, with con - include: stant thickness across the strip . On the other hand, I Work rolls may be tilted out of some applications require a positive profile, a lit - Roll tilting: parallel vertically to counteract and correct prod - tle thicker toward the middle than toward the uct surfaces which are non-parallel in the opposite edges. direction. The formation of a required strip profile is I most readily achieved on thick, hot metal: that is, Roll crossing: Work rolls may be “crossed” during single-stand hot rolling or in the entry and (made slightly non-parallel horizontally) by mov - middle rolls of a hot-rolling tandem mill . ing their end-mountings, to alter the distribution The flatness of the final product depends more of rolling forces. This type of adjustment is made heavily on the rolling applied by the last mill between rolling passes. stand it passes through, its exit stand. Achieving I Localized roll cooling: Controlled increases the best possible flatness is usually one of the or decreases of cooling application to localized main objectives of cold rolling. segments of rolls may be used to control thermal Thickness control, of course, is practiced at expansion and contraction, and so control roll every rolling step; but it is most critical in the last shape during rolling. This can be a significant reduction stand which gives the product its final control technique for cold rolling. thickness. I In order for thickness and profile to be effec - Roll -bending: Work rolls or backup rolls may be bent in either the vertical or the horizontal tively controlled, they must be both accurately plane, to compensate for rolling forces or to measured and accurately corrected. Modern com - correct an incoming profile. Roll -bending can be puterized rolling technology makes it possible to controlled dynamically, during rolling. measure the thickness, flatness and profile of a I product as it comes out of the mill stand , compare Stepped backup rolls: Backup rolls may be them with specified values, and adjust the rolling installed with larger-diameter cylindrical center I SHEET ROLLING OPERATIONS 5-10

sections and smaller-diameter ends, to concentrate work rolls are used together, the shape of the gap their pressure on the work rolls just over the width between them can be varied by shifting them axi - of the rolled product. The “step” width may be a ally in opposite directions. Moving the two con - ground-in fixed feature of the back-up roll , or it cave segments opposite each other allows the may be adjustable, created by shrink-fitting product passing between them to bulge in the removable outer sleeves or sleeve segments on the middle, either forming a crowned profile or core roll . Stepped rolls are installed or adjusted correcting an undesired concavity. Moving two between rolling passes. convex segments into opposition squeezes middle I of the product and forms a concave profile or Axial shifting of sleeved backup rolls: A corrects unwanted crowning. Placing convex sleeve fitted on a backup roll may be moved from and concave segments into opposition creates a side to side by sliding the sleeve along the roll , product with constant transverse thickness but a shifting the area of pressure against the work roll . “wavy” profile which may require flattening by The sleeves of upper and lower backup rolls may subsequent rolling. be moved in the same, or in opposite, directions I depending on the type of correction needed. Flexible backup rolls: Backup rolls have Because these sleeves are shrink-fitted on their been made available which can be expanded cores, they can be shifted only between rolling hydraulically at the center or at the ends to induce passes. crowning or concaving dynamically during I rolling, in response to sensor/ computer feed-back Axial shifting of cylindrical work rolls : loops. In addition, a “self compensating” backup Conventional cylindrical work rolls may, them - roll , more flexible at its ends than at its middle, selves, be shifted from side to side to redistribute combats unwanted product crowning by offering their pressure against the product. The upper and elastic resistance roughly in proportion to the vari - lower work rolls may be shifted in the same or in ous degrees of separating force all across the roll opposite directions. Shifting is carried out gap . Flexible backup rolls also extend the effec - between rolling passes. tive range of work roll bending. I Axial shifting of non-cylindrical work rolls : Some of these techniques may be applied in com - Instead of the conventional straight cylinder, work bination with others. The choice of measurement rolls may be made with a wave-shaped profile systems, feedback loops, and actuator systems for from end to end; that is, a slightly convex form any specific rolling mill depends on that mill’s toward one end, changing smoothly into a slightly own products and operating conditions. concave form toward the other. When two such

TEXTURING AND EMBOSSING Some products — such as the aluminum tread plates of decks and steps — call for texturing or embossing during the final rolling. Instead of the usual smooth surfaces, one or both work rolls will have a pattern which is transferred to the sheet as it passes through, during rolling or subsequent finishing operations, and often by the last stand of a tandem mill . I Embossing: Coiled sheet is run through set of metal, embossing does not appreciably reduce the rolls with the purpose of transferring a special pat - metal thickness. Embossed aluminum sheet with tern from engraved rolls onto surface of the coil. specific patterns such as “wood grain” or “dia - Unlike during the fabricating of tread plate where mond” is widely used in architectural applications. a deeper pattern is extruded on one side of the I SHEET ROLLING OPERATIONS 5-11

SELF-TEST QUESTIONS 5.6 If an ingot is rolled to 1/2 of its original thickness, its length... SECTION 5: SHEET ROLLING a. becomes half the original length. 5.1 A breakdown mill … b. remains unchanged. a. is of a vastly different design from c. becomes 50% longer than the original non-breakdown mills. length. b. is the first mill to apply rolling where d. becomes twice as long as the original there are more mills than one. length.

5.2 The purpose of a coolant /lubricant 5.7 “Cross-rolling ” means rolling an ingot ... spray system is to: a. faster. a. remove excess heat generated during b. sideways. the thickness reduction. c. thinner. b. control flatness . c. minimize variation in the roll gap 5.8 Cross-rolling rolling is done to increase... along its length. a. productivity. d. all of the above. b. speed. c. width. 5.3 During ingot breakdown, a reduction in thickness of ____ per pass is not extraor - 5.9 A group of two or more mill stands or dinary. ranged so that the aluminum plate or a. 0.02" (0.5 mm) sheet is successively rolled by each b. 0.2" (5 mm) stand during the same pass is called... c. 2.0" (50 mm) a. a cold mill. b. a hot mill. 5.4 In a breakdown mill , the ingot or slab is c. a cluster mill . positioned for rolling by the… d. a tandem mill . a. work rolls . e. a breakdown mill . b. backup rolls. c. table rolls . 5.10 Which, if any, of these factors affects d. roll gap . sheet tension between the stands of a tandem mill ? 5.5 When a slab is rolled normally, a. Sheet thickness. its width… b. Roll power relationships. a. increases by about 10x. c. Take-up coil diameter. b. changes little. d. Roll gaps. c. decreases. e. None of the above.

Why? 5.11 Annealing is performed for which, if any, of these reasons? a. To remove precipitation hardening . b. To strengthen the alloy. c. To remove impurities. d. To remove work hardening . e. To remove recrystallization. f. None of the above. I SHEET ROLLING OPERATIONS 5-12

5.12 Recrystallization occurs… 5.20 The main purpose of the coolant system a. suddenly at a precise temperature. in the cold rolling mill is to... b. gradually over an effective tempera - a. maintain the work roll dimensions. ture range. b. achieve the temper in the sheet. c. in sharp steps at several different tem - c. both. peratures. d. neither. d. only after remelting. 5.21 Llist five product characteristics that are 5.13 What is the term used to signify that affected by cold rolling. metal has been heated above its recrystallization temperature ?

5.14 “Some recrystallization or annealing can take place during hot rolling .” This state - 5.22 The fastest cold rolling mills reach ment is: speeds of more than… a. true. a. 3000 ft./min. (915 m) b. false. b. 5000 ft./min. (1525 m) c. 7000 ft./min. (2135 m) 5.15 “Full anneal”, “partial anneal”, and “stabilize” are the thermal process terms 5.23 Name at least four techniques or related to… “actuators” available to control gauge a. the alloy. and/or profile during rolling. b. the type of furnace. c. the purpose and practice.

5.16 The purpose of controlled atmosphere annealing is to avoid... a. oxidation of the residual oils. b. oxidation of the Mg in some alloys . 5.24 Tread plate is usually produced by… c. a and b. a. hot rolling . d. Neither. b. cold rolling. c. a finishing operation. 5.17 The primary reason for stabilizing 5xxx- series alloys is to… a. prevent age softening. b. improve corrosion resistance . c, optimize finishing characteristics. d. all of the above.

5.18 Some heat-treatable alloys are sold in O- temper because... a. the government requires it. b. forming requirement is severe. c. the cost is lower.

5.19 Brightness of final as-rolled surface finish is most affected by… a. the amount of reduction. b. the alloy. c. the finish of the work roll . Rolling Aluminum: From the Mine through the Mill 6 SHEET FINISHING When rolling is completed, the coiled sheet goes through selected finishing processes.

SOLUTION HEAT TREATING Heat-treatable alloys may, at this point, be solution heat- treated. The sheet is conveyed through a furnace at the right temperature, for the right amount of time, to dissolve alloying elements more completely. At the exit of the furnace, the sheet is rapidly cooled i.e. “quenched” to retain the microstructure that existed at the high temperature. Solution heat treating should not be confused with annealing . Although both processes apply heat, annealing softens the metal; solution heat treating and quenching strengthens it. But a dislocation itself, if it is not locked in Metallurgical Function place, can be pushed along its plane by an applied of Solution Heat Treating he atoms of every solid metal are naturally force, like a hump in a rug that simply moves arranged in regular, repeating patterns that form someplace else if you step on it. A dislocation can cTrystals. Aluminum atoms tend to form repeated block plane slippage only if it stays in place and joined cubes that share their boundaries, just as resists the slip instead of moving along with it. rooms in an apartment building share walls, floors When a molten aluminum alloy solidifies during and ceilings. This arrangement of joined cubes is casting, the atoms of its dissolved alloying ele - called the crystal’s “ lattice .” Cube walls that line ments tend to cluster (precipitate) into relatively up with one another in any direction are said to lie large particles visible under a microscope. in the same lattice plane. Large particles are essentially separate from the When the shape of solid metal is changed by metal’s crystal lattice . Dislocations can travel force — that is, deformed — its atomic lattice is around them, much as waves in water can detour rearranged. Normally, this means that parallel around an isolated rock and continue past it. lattice planes are forced to slip past each other. Smaller, submicroscopic particles or individual Any condition that resists the slipping of lattice alloying atoms, however, become closely integrat - planes stiffens the whole lattice and makes the ed with the aluminum crystal lattice . Their pres - metal mechanically stronger. ence tends to “pin down” lattice dislocations in In practical metal products, crystal lattices are two ways. never perfect and their planes are not smooth and Because they don’t fit in as neatly as the crys - unbroken. Here and there, the repeated pattern tal’s natural element, aluminum, other elements gets out of step and the plane is “dislocated.” create stressed areas that resist the movement of Dislocations hinder lattice planes from slipping dislocations, because it takes more energy to past each other, creating resistance to deformation move dislocations around stressed areas. in the bulk metal. Alloying elements are introduced It also takes more energy to force a dislocation to create just that effect, strengthening the alloy through a stressed area instead of around it. Both by further distorting the crystallographic lattice . ways, dislocation migration is strongly impeded, and the metal is strengthened against deformation. I SHEET FINISHING 6-2

The purpose of solution heat treating, then, is to dissolve large particles and disperse them as Quenching smaller precipitates or dissolved atoms capable of issolved elements can move more freely pinning down dislocations and strengthening the through an alloy when its lattice structure is product. aDbsent (in the molten state), incomplete or weak, at high temperatures, than they can once the lat - Solution Heat Treatment : “Soaking” tice is fully formed, cool and rigid. olution heat treatment ” usually refers to a If a solutionaized alloy were allowed to cool three-stage process in which solution heat - slowly, its dissolved, dispersed elements would be “Sing is the first step. That is followed by quenching partially squeezed out of the forming crystal lat - and then aging . tice and would cluster together in large particles Solution heating consists of raising the alloy to with little strengthening influence. the desired temperature and then holding it at that This is prevented by “ quenching ” the hot alloy; temperature — “soaking” it — for the necessary that is, cooling it in a time too short for the dis - amount of time to dissolve alloying elements. solved elements to migrate. This, in effect, freezes This dissolving (solutionizing) must take place dissolved elements where they are, still dispersed in solid metal. Melting the alloy would only repeat in what becomes a “supersaturated” solid solution the casting conditions that form large particles. holding more alloying elements in solution at The degree to which solid aluminum can hold room temperature than would otherwise occur unprecipitated elements in solution is called its with a slow cool down. “solid solubility ”. When solid aluminum is heated, To achieve this condition, the alloy must be the solid solubility of important alloying elements cooled very quickly through the temperature range in it is increased and precipitated elements can in which particle precipitation would otherwise redissolve. occur. The aim is to retain the “supersaturated” solid Therefore, the alloy is held at a temperature solution all the way down to room temperature. Quenching is usually accomplished by plunging below its melting point but high enough to produce heat-soaked metal into cold water or flushing a nearly homogenous solid solution . The solution water over it at high flow rates. heat treating temperature must be selected and Milder quenching methods, such as water spray, carefully controlled for each aluminum alloy, hot or boiling water, air blast or water-mist “fog”, because the range between the solution may be used on some alloys whose heat treated temperature and the melting point may be quite properties are less sensitive to the quenching rate. narrow, as illustrated by these examples of three Milder quenching may minimize distortion and alloys , all in the 2xxx series: residual stress in the metal, reducing the need for Alloy Solution Treating Eutectic Melting straightening operations. Temperature, °F (°C) Temperature, °F (°C) Immediately after quenching , when alloying ele - 2014 925-945 (496-507) 945 (507) ments are still in solution and have not had time 2017 925-950 (496-510) 955 (513) to form small dislocation- pinning precipitates , 2024 910-930 (488-499) 935 (502) most aluminum alloys are almost as ductile as in the annealed condition. Therefore, straightening In these examples, the lowest effective solution operations are often carried out as soon as possi - temperature is only 20 to 25°F (11-14°C) short of ble after quenching to take advantage of this soft - the melting point . One of these alloys soaked at a ened condition. temperature in the middle of its solution range Rolling or other cold working in this condition would be only 15°F (8°C) below the melting tem - may further improve the properties of some heat perature. Thus, temperatures must be strictly con - treated alloys . trolled during solution heat treatment . Modern mills use “continuous strip ” heating and The “ soak time” required for adequate solution quenching . In this system, uncut sheet runs con - varies depending on the thickness of the metal and tinuously through a tunnel-type furnace and an its initial microstructure. It can range from min - adjacent quenching station. utes to hours after the metal has reached solution temperature. I SHEET FINISHING 6-3

Natural Aging Artificial Aging (Precipitation Hardening ) (Precipitation Heat Treatment) he increased strength which is the usual pur - any other alloys , however, harden slowly at pose of solution heat treating develops only room temperature, continuing to strengthen Tduring its final step, aging or “ precipitation aMppreciably for years. Those alloys are treated to hardening .” accelerate precipitation by “artificial aging ”: The elements dissolved in a supersaturated, holding them for a limited time at a mo derately solid solution can still migrate through cool metal, raised temperature, which increases the mobility even at room temperature, but not as fast or as far of dissolved elements and allows them to precipi - as they could at high temperatures. As a result, tate more rapidly than at room temperature. atoms of dissolved alloying elements can slowly This process is also called “precipitation heat gather to form tiny precipitates with relatively treatment”. short distances between them, but not large, wide - Even alloys which naturally age rapidly may ly-spaced particles. The large number and high be artificially aged to assure the development of density of small dislocation- pinning precipitates maximum strength . The strength of some alloys gives the alloy its strength and hardness . can be maximized by applying a combination of Aging means allowing enough time for this to treatments: a small amount of cold working, fol - happen before the metal is used for its intended lowed by artificial aging . applications. Solution heat-treatment and quench - Precipitation heat treatment temperatures gener - ing have established the necessary conditions for ally range between 240 to 375°F (115-190°C), and dislocation pinning to occur; aging allows it to soak times vary from about 5 hours to 48 hours. take place. The time/temperature cycle for each alloy is This may occur during “ natural aging ” at room selected to achieve the most suitable compromise temperature. Some alloys , particularly those in the between the conflicting demands of product copper-alloyed 2xxx series, reach virtually maxi - strength and ductility , and other required charac - mum strength by natural aging in a short time—a teristics such as corrosion resistance . few days or weeks—while others continue to gain Artificial aging can be deliberately carried strength appreciably by precipitation hardening beyond the point of maximum alloy strength . By for years. In alloy 2024, for example, precipitation promoting the controlled growth of somewhat hardening is essentially complete after about four larger precipitates and thus reducing strength and days at room temperature, achieving the T3 or T4 hardness , certain specified product properties are temper . Alloys 2014 and 6061, sometimes used in achieved. This procedure is called “ over- aging .” the T4 temper , reach fairly stable precipitation These variations in treatment are reflected in the conditions after about one month at room different definitions of the T3, T4, T6, T7, T8 and temperature. T9 aluminum alloy tempers, and the progressively aging “W” tempers. It should be noted that precipitation hardening can also be slowed down to some extent by reduc - ing temperature. For some purposes and in some alloys , aging can be slowed or delayed for several days by refrigerating the metal at zero°F (-18°C) or lower. Forming or straightening may induce desirable property changes if performed before significant aging (precipitation) has occurred. When these procedures cannot be carried out immediately after quenching , the alloy may be refrigerated to retard aging until the metal can be worked more conveniently. I SHEET FINISHING 6-4

SLITTING Coiled sheet is then run through a high-speed slitter, whose circular knives trim the edges straight. The slitter may also divide wide sheet into narrower coils of specified widths. he slitter may be used not only to trim the emerges from the slitter. edges of wide sheet, but it may also cut sheet A high-speed slitter applying a surface lubricant Tinto narrower strips down to widths as small as electrostatically may process sheet at a rate up to 1/4 inch (6.3 mm) according to the customer's 4000 feet per minute (1220 m/min.). A laser scan - specifications. The slit sheet is recoiled as it ner simultaneously checks for surface defects.

TENSION- LEVELING Before or after slitting , the sheet may also go through a tension-leveler . There, it passes over sets of rolls that flex and stretch the metal to remove any buckling and give it a uniform flatness . he tension-leveler flattens rolled strip by Surface Finishes stretching it to a predetermined, exactly con - Aluminum sheet and plate emerge from rolling tTrolled percentage of elongation. The sheet is kept with a surface largely determined by the smooth - in tension by the grip of entry and exit bridle rolls. ness of the work rolls employed. Various other In between the entry and exit bridle rolls, the surface finishing operations may be performed sheet passes over and under a series of steel rolls. after rolling is completed, to enhance product This bends and works the sheet beyond its elastic appearance, improve surface characteristics, or limit and produces permanent elongation which increase corrosion resistance . counteracts any remaining curvature and com - Most surface finishing methods fall under one pletes the straightening process, producing an of three general categories: mechanical finishes, alloy strip which is flat and stress-equalized. chemical finishes, and coatings.

Configuration of tension leveler rolls (schematic drawing). I SHEET FINISHING 6-5

Mechanical Finishes for sheet and plate include: Oiling Buffing heet and plate products may be coated with Polishing oil to prevent oxidation, water staining and Sanding sScratching during handling, storage and shipping Scratching (unless they have been given a specific surface Grinding finish which should not be oiled). Sheet and plate Burnishing products destined for overseas shipment are usual - Embossing ly oiled. Customers purchasing sheet and plate Chemical Finishes for sheet and plate include: sometimes request that it be given a uniform Etching coating of oil which will ease later metal forming Anodizing operations. The oils used for these purposes usual - Chemical brightening ly have a mineral oil base and are formulated to Conversion coating provide high resistance to water while avoiding Zincate coating skin irritation among handlers.

Coatings for sheet and plate include: Degreasing Priming ust the opposite procedure, degreasing , Painting is applied to remove any oils remaining Porcelain enameling Jon sheet or plate from the rolling operation, when a customer orders an oil-free product. Finishes and coatings may be applied singly or in combination as required for the intended product.

COATINGS AND MARKINGS Coatings or decorations may also be applied. Paint, enamel or other liquids are usually sprayed or rolled on. Paper, plas tic or other films may be applied using adhesives, pressure and heat. Some aluminum rolling mills have their own coating lines, but this type of finishing is often done elsewhere.

also be required by federal or military Stenciling hen ready identification of finished sheet is specifications. essential, codes identifying the product’s In recent years, systems have been developed sWpecifications, alloy, temper , gauge, and manufac - for marking aluminum sheet and plate with bar turer may be stenciled on it by inked rollers or codes that can be read automatically by computer - other marking devices. Stenciled markings may linked laser scanners.

CUTTING TO LENGTH When separate flat sheets are required, coiled sheet is sent to a “cut-to-length” line. There, it is uncoiled and cut to the specified lengths. 2. It may unroll from the coil and be cut to length oiled sheet may be cut to length in one of two by “ flying shears ” that travel with the moving ways: sheet while they cut it. C A mechanical stacker using forced air or vacuum 1. Sheet unrolled from a coil may be momentarily lifters lowers cut sheets onto the stack gently, to stopped and cut to a pre-set length by stationary avoid scratching. shears. I SHEET FINISHING 6-6

STRETCHER- LEVELING If necessary, cut sheets are stretched to flatten them. ut sheet may be further flattened by a sheet stretcher. This device clamps the ends of the sCheet between pneumatically activated jaws. Then these stretcher heads are hydraulically separated, stretching the sheet to a preset amount. Stretcher- leveled sheet is important to many applications, such as smooth truck body panels whose wide expanses would make any irregularity more noticeable.

PACKAGING AND STORAGE Finally, the finished sheet is packaged and stored for shipping. The ends of coiled sheet are sometimes welded to the inside and outside of the coil to prevent uncoiling. Then the coils are wrapped in plastic to keep out moisture and are banded.

oiled sheet is usually wrapped and sealed readily removed by hand or by air blown between against moisture as a unit. Flat sheet is also the coating and the metal surface. This film pCrotected, usually by separating stacked sheets should be removed within ~90 days or as recom - (“interleaving”) with an anti-tarnish, noncorrosive mended by the supplier. Leaving the film on for craft paper. longer periods can result in problems with its Flat sheet surfaces may also be protected removal. temporarily by gummed tape, which should be Flat sheet may be packaged for shipping in a removed within 90 days after its application. variety of ways, such as: bare metal in a strapped Another protection method for some sheet prod - bundle; a paper-wrapped bundle; or inside a fiber ucts is a thin transparent vinyl film which can be or wood box or a reusable shipping container. I SHEET FINISHING 6-7

SELF-TEST QUESTIONS 6.6 Maximum strength is not achieved in a heat treatable alloy unless it is... SECTION 6: SHEET FINISHING a. formed. b. artificially aged. 6.1 Solution heat treating involves dissolving... c. naturally aged. a. copper. b. lattice dislocations. 6.7 Tension leveling uses both tension and c. alloying elements. bending or flexing for flattening and to a. prevent scratches. 6.2 In solution heat treating, “soaking” b. equalize stresses. means... c. remove coil set. a. wetting the alloy before heat-treat - ment . 6.8 Most aluminum surface finishing meth - b. heating the alloy long enough to ods fall under one of three general cat - dissolve its alloying elements. egories. Name them. c. quenching heated alloy in cold water. d. remelting the alloy to add new elements.

6.3 Solution heat treatment temperature 6.9 In recent years, systems have been may be critical because... developed to mark aluminum sheet and a. precipitation may occur. plate with… b. melting temperature is close. a. photo-engraved symbols. c. solid solubility is limited. b. coded magnetic stripes. c. laser-scanned bar codes. 6.4 The purpose of quenching is… d. laser-burned engraving. a. to freeze dissolved elements where they are. b. to make dissolved elements cluster into large particles. c. to cool heat-treated metal to room temperature for ease of handling. d. to establish the right temperature for further rolling.

6.5 The purpose of aging after solution- treating and quenching is... a. to achieve specific length and width dimensions. b. to achieve stable precipitation conditions. c. to thicken aluminum's natural oxide film. d. to produce a specified surface finish.

Rolling Aluminum: From the Mine through the Mill 7 PLATE ROLLING & FINISHING Aluminum plate and sheet products are rolled and finished by essentially similar procedures. PLATE ROLLING A slab rolled in the breakdown mill to four to five inches (100- 125 mm) is already thick plate. For some applications it is sent straight to the finishing line. Thick plate is machined by customers into more elaborate shapes. Otherwise, the breakdown mill may continue rolling thick plate down to a thinner gauge. Final thickness may be achieved in a second hot-rolling stand, for closer control or simply for efficiency. Sometimes plate is also cold-rolled to increase its strength or improve flatness . Plate for boat structures or military armor may be reduced 30 percent in thickness by cold-rolling, to increase its strength . Plate remains uncoiled and flat all through its processing. It is often transported between work stations by a crane equipped with vacuum pads.

Slab Reheating Intermediate Edge Trimming fter its initial breakdown reduction, the slab is lates of some alloys may crack along the edges advanced on a run-out table where its ends during rolling. Such cracks would invade the aAre trimmed square. Occasionally, slabs destined pProduct during subsequent rolling if they were for further rolling into plate are then transferred to allowed to remain. Therefore, after intermediate a furnace for reheating which may take from two rolling the plate’s edges are trimmed to remove to 24 hours, depending on the alloy. Restored to such cracks, leaving it wide enough for trimming rolling temperature, they are moved to the inter - to final size when rolling is completed. Both ends mediate rolling mill. are also trimmed square.

PLATE FINISHING Alter rolling, heat-treatable plate goes through a horizontal or vertical furnace for solution heat treating and quenching . I PLATE ROLLING & FINISHING 7-2

surface of hot plate to reach its center. During that Solution Heat Treating time large temperature differences can develop, and Quenching he solution heat treating, quenching , and pre - setting up mechanical expansion/contraction cipitation hardening of aluminum plate follows stresses between surface and core which become tThe same physical laws and practical procedures frozen into the cooled plate and are permanent as for aluminum sheet. The procedures may have unless relieved by further operations. to be adapted to take into account the greater Tests on two-inch-thick (50 mm) plate (alloy thickness of plate. 7075) have found as much as 350ºF (195ºC) dif - Because the rate of heat transfer through metal ference between surface and core, four seconds is limited, it takes time for cooling applied at the after the start of quenching .

PLATE STRETCHING Thick plate is stretched between the gripping jaws of a hydraulic machine, to flatten it, work-harden it, and relieve stresses created by rolling and heat-treating. A large stretch - er can apply as much as 15,000 tons (133 meganewtons) or more of tension! Thinner heat-treated plate is often stretched as well. But non-heat-treated thin plate is not usually stretched unless it’s necessary for flatness . Plate may be stretched by as little as one percent, or as much as 15 percent of its original length. The stretcher’s grip imprints the ends of the plate, so they are sawed off and recycled. tretching has proven to be an effective means A stretcher applying 6 million pounds (27 of relieving stresses introduced into plate by meganewtons) of tension can relieve and level Squenching . aluminum plate up to three inches (75 mm) thick. For the alloys , tempers and applications that A stretcher with 30 million pounds (133 account for almost all rolled plate production, meganewtons) capacity can stress-relieve alu - stretching is typically within the range of one to minum plate up to six inches (150 mm) thick or three percent. In some specialized cases, such as larger. alloys 2024 and 2219 in the T86 and T87 work- Stress-relief stretching has made it possible to hardened tempers produced to meet demanding machine thick plate into complex structural air - aerospace requirements, stretching of as much as craft parts with integral stiffeners, without the 15 percent may be applied. distortion that might occur if the stresses were not first relieved.

ULTRASONIC INSPECTION At this point, aluminum plate may be ultrasonically inspect - ed. It is submerged in water and sound waves are beamed into it. They will bounce back from hidden flaws, revealing their presence and their location. Flawed plate, of course, is not shipped but is held back for correction or recycling . I PLATE ROLLING & FINISHING 7-3

ltrasonic testing may be required for some The ultrasonic waves are reflected back to a products, particularly under certain military detector from both surfaces of the plate. Since the sUpecifications. On less critical products it may be speed of sound through the aluminum alloy is used to spot-check samples for production quality. known, the time difference between the arrival of For ultrasonic testing, a slab or plate is sub - reflected waves from the two surfaces can be used merged in water in a large shallow tank nick - to calculate the distance between them and the named the “swimming pool.” The water serves as thickness of the plate. an efficient coupling agent which aids in transmit - Hidden flaws within the metal will distort or ting sound waves at frequencies above human reflect the sound waves as well. These flaws can hearing (ultrasonic) from a transducer into the be revealed and even located by the reflected tested metal. patterns.

ARTIFICIAL AGING After stretching and inspection , some plate is further hard - ened by undergoing a moderately raised temperature to accelerate its natural aging . The process is called “artificial aging .”

he natural aging and artificial aging of aluminum are the same for sheet and plate and the procedures alloys are discussed above in the “Solution Heat and temperature/time cycles are governed primarily Treating” section under “Sheet Finishing.” by alloy composition and property spec ifications The principles of aging (precipitation hardening ) rather than product form.

Plate edges are usually trimmed square and PLATE EDGE CUTTING flat. Customers may, however, specify special At some convenient stage, plate edges are trimmed straight by edge preparations such as: rabbeted, routed, circular saws. machined or anodized.

PLATE INSPECTION , SUPERFICIAL DEFECT REMOVAL AND STORAGE Finally, the finished plate is inspected; any minor surface defects are removed, and the plate is stacked and stored for shipment—protected by plasticized paper and often separat - ed by wooden spacers. I PLATE ROLLING & FINISHING 7-4

NOTES I PLATE ROLLING & FINISHING 7-5

SELF-TEST QUESTIONS 7.5 Plate is typically stretched… a. less than one percent. SECTION 7: PLATE ROLLING AND b. 1-3% FINISHING c. 5-1O% d. 12-16% 7.1 Plate is cold rolled in order to… a. increase its strength . 7.6 A hydraulic stretcher… b. achieve special thickness tolerance. a. leaves no marks on stretched plate. c. improve its flatness . b. makes the plate ends smoother than d. all of the above. the rest. c. leaves end imprints which become 7.2 Plate solution heat treating is normally part of the finished product. done... d. leaves end imprints which are sawed a. in a horizontal or vertical furnace. off. b. to improve flatness . c. using air quench. 7.7 In some products, trimming is done before final rolling in order to… 7.3 The quenching of solution-heated plate a. make the final trim easier to can set up internal stresses because the dispose of. plate… b. remove edge cracks. a. cools faster on one side than the c. inspect the product as early as other. possible. b. cools faster at the interior than at the surfaces. 7.8 Ultrasonic testing is done to… c. cools faster at the surfaces than at a. detect inclusions . the interior. b. satisfy OSHA requirements. d. cools faster at the ends than at the c. check hardness or strength . middle. 7.9 The principles of natural and artificial 7.4 Stretching relieves stresses by… aging of aluminum plate… a. allowing all the grains to line up. a. are essentially the same as for sheet. b. raising unequal stresses to a higher, b. are entirely different than for sheet. more equal level. c. depend on the shape of the finished c. cold working the metal. product. d. None of the above.

Rolling Aluminum: From the Mine through the Mill 8 QUALITY & PROCESS CONTROL TESTING AND INSPECTION At every major step of aluminum sheet and plate rolling , product quality is checked—not only in general, but against the specifications required for each batch. Orders are rolled to each customer's specification… that is, custom made. A large aluminum rolling mill will have a well-equipped laboratory which can routinely analyze alloy composition within minutes… Test the strength of product samples… Inspect metallurgical structure microscopically… Detect porosity with a dye that glows under ultraviolet tight… And analyze rolling coolants and lubricants.

heet and plate products are routinely tested and computer , which immediately compares the tested inspected in accordance with certain govern - strength with the specifications. If the sample is Sment and society specifications and good business within specifications, the computer automatically practice. The testing routinely performed is transmits an alloy clearance to the appropriate frequently sufficient to ensure the quality required plant operator. If not, it reports that the sample is by the customer. out of specifications. Additional tests or inspections may be arranged by agreement between the customer and the Microscopic Inspection producer. he surface of an alloy sample is polished, chem - Some of the additional tests which may be ically etched to enhance grain boundaries and ordered include: oTther metallurgical features, and then inspected I Squareness inspection visually under a light microscope. Such inspection I Electrical conductivity testing can reveal grain sizes, inclusions , defect identifi - I Fracture toughness testing cation and other features of alloy structure, and cladding thickness. And, for plate: If necessary, samples can be subjected to magni - I Ultrasonic inspection I Ballistic testing fications as high as 100,000 times or more by electron microscopy at appropriate facilities.

Tensile Strength Testing Porosity Testing n the rolling mill laboratory, the tensile strength orosity can be observed and estimated by of an aluminum alloy is tested by stretching a applying to the surface of an alloy sample sIample, of standard thickness and shape, in a aPpenetrating liquid dye which concentrates in machine which measures the force required to pores. This dye contains chemicals which fluo - deform and then break it. A computer automatical - resce — that is, emit visible light — when ly records these measured yield and tensile exposed to invisible ultraviolet light. Thus, the strengths and reports the results. In a computer - treated sample reveals its porosity when inspected ized rolling mill, the control center may already under UV light in a darkroom. have entered the alloy batch specifications into the I QUALITY & PROCESS CONTROL 8-2

(1000 mm) wide, up to 59.06 inches (1500 mm), Coolant / Lubricant Analysis he liquid coolants / lubricants used in rolling the standard tolerance is increased to a permitted aluminum can be chemically analyzed automat - thickness deviation of no more than .0025 inch iTcally. In as little as five to ten minutes, such (0.06 mm) . devices can detect and measure the presence of esters, acids, soaps and contaminants. They can Surface Quality Characteristics provide information about conditions prevalent in lat-rolled aluminum may be produced with one the rolling process. In addition, viscosity and dis - of a number of common types of surface quali - tillation curves can be determined. Such factors tFies, including: exert important influences on rolling speed and product surface quality . Mill finish : The general-purpose surface finish, which meets most customer needs, produced by work rolls sur - Anodizing and Bright-Dipping Tests f a batch of flat-rolled aluminum is eventually to faced mainly for effective thickness reduction. be anodized or bright-dipped, samples may be gIiven these treatments in small laboratory facili - Skin-quality finish : ties to confirm that the metal will perform as High surface quality on one side of the flat-rolled intended. product, with mill finish on the other side.

Dimensional Tolerance Control One-side-bright mill finish : tandard dimensional tolerances for aluminum Moderately “bright” (reflective) surface on one sheet and plate are promulgated by the side, with mill finish on the other side. SAmerican National Standards Institute and pub - lished in ANSI H35.2 (and H35.2M, the metric Standard one-side-bright finish: version). Uniformly bright surface on one side, with mill ANSI H35.2 includes dimensional tolerances for finish on the other side. thickness, width, length, lateral bow, squareness and flatness , and other tolerances applicable to Standard bright finish : specific types of products. A relatively bright surface on both sides. Sheet and plate are produced within these ANSI tolerances unless other tolerances are specified. Other aspects of flat-rolled aluminum surfaces Producers may publish their own standard toler - are discussed and illustrated in The Aluminum ances , which govern where they differ from the Association's publication, “Visual Quality ANSI tolerances . Characteristics of Aluminum Sheet and Plate” Nonstandard tolerance specifications may be (QCA-1;2002). adopted by mutual agreement between the cus - This booklet identifies more than 90 characteris - tomer and the producer. tics of bare and Alclad sheet and plate, grouped The ANSI tolerances usually applied impose under five general headings: limits on dimensional deviations, which vary with Flatness Characteristics alloy and with specified product thickness and Metallurgical Characteristics width Surface Characteristics For example, sheet rolled from alloy 5052 or a Other Characteristics number of other specific alloys to a specified Coated Sheet Characteristics. thickness of 0.030 inch (0.75 mm) at a sheet width up through 39.37 inches (1000 mm) may The booklet describes and illustrates the visual deviate from its nominal thickness by no more appearances of various flaws which may be than 0.0020 inch (0.045 mm) under the ANSI caused by deviations from optimal rolling condi - Standard Tolerance table. tions or by handling and storage conditions. If the same sheet is more than 39.37 inches I QUALITY & PROCESS CONTROL 8-3

COMPUTERIZED AND CENTRALIZED CONTROLS In a modern mill, each rolling stand and many finishing operations may be computer -controlled for high quality and uniformity. And operators at a control center direct alloying on the basis of lab tests, and coordinate movements of scrap, alloy, and rolled products throughout the plant. The aluminum rolling industry is moving increasingly toward computerized process coordination and the tracking of materials and products by automatic bar-code reading.

s computerization spreads and develops, Just-In-Time (JIT ) systems coordinate plant uti - modern aluminum rolling plants are increas - lization and production schedules with customer Aingly adopting such techniques as “ computer -inte - orders and product delivery timetables to reduce grated manufacturing”, “just-in-time production”, or eliminate unnecessary stockpiling and unantici - and “ statistical process control ” to improve effi - pated production changes, and guarantee product ciency, customer service and product quality. delivery when the customer needs it.

Statistical Process Control (SPC) systems regu - Computer -Integrated Manufacturing ( CIM ) larly measure key product and process characteris - systems use the computer , connected to sensors tics; automatically analyze them in relation to and other information-inputs, to organize and con - product specifications; identify trends if changes trol the flow of materials through the rolling plant start to occur; and feed back these findings to and to automate rolling operations, improving process controllers which make the necessary plant efficiency and product uniformity. adjustments to keep processes and products within specifications.

Aluminum plate, sheet and foil look so simple—and it’s so easy to make so many things out of them—that it’s hard to imagine how much technology, power, and care has gone into them. The modern rolling mill applies massive physical force with fine precision, producing flat aluminum products with accu - rate dimensions and with properties tailor-made to meet the customer's needs. In the race for product versatility, durability, performance, economy, and ease of fabrication, it’s hard to beat aluminum plate, sheet and foil —they’re really rolling! I QUALITY & PROCESS CONTROL 8-4

NOTES I QUALITY & PROCESS CONTROL 8-5

SELF-TEST QUESTIONS 8.4 Among recent rolling mill developments, the acronym “ CIM ” stands for; SECTION 8: QUALITY AND PROCESS a. Comprehensive Inventory CONTROL Management. 8.1 Every ingot “drop ”, when finished into b. Computer -Intensive Mechanics. rolled product, is tested for dimensions, c. Complex-Intelligence Machines. mechanical properties, and… d. Computer -Integrated Manufacturing. a. anisotropy. b. hardness . 8.5 A “JIT” system… c. alloy composition. a. coordinates production and delivery d. all of the above. time tables. e. b and c. b. stockpiles product for potential future orders. 8.2 “Analysis of used coolant / lubricant c. automatically audits employee can detect contaminants, but it can not work-hours. reveal anything about the rolling d. forecasts market trends for rolled process itself.” This statement is: products. a. true. b. false. 8.6 “Statistical Process Control ” (SPC)… c. a “trick question”. a. improves the accuracy of company record-keeping. 8.3 “Standard dimensional tolerances ” are b. monitors rolling industry business applied to aluminum sheet and plate statistics. products… c. heads off potential rolling-process a. in all cases. problems. b. only when required by government d. matches ingot production with orders specifications. for rolled products c. only when required by individual purchasers. d. unless special tolerances are specified. Rolling Aluminum: From the Mine through the Mill 9 GLOSSARY

Aging —Precipitation from solid solution result - Products”, published by the Aluminum ing in a change in properties of an alloy, usually Association; also published as ANSI -H35.2(M) in occurring slowly at room temperature ( natural metric units. aging ) or more rapidly at elevated temperatures —Precipitation from solid solu - (artificial aging ). Artificial aging tion resulting in a change in properties of an alloy, Alclad sheet —Composite sheet consisting of an accelerated by application of a moderately elevat - aluminum alloy core having on both surfaces (if ed temperature. on one side only, Alclad One Side Sheet) a metal - —In a rolling mill, supporting rolls lurgically bonded aluminum or aluminum alloy Backup rolls which press against the work rolls to counteract layer that is anodic to the core, thus electrolytical - deflection forces. ly protecting the core against corrosion. —Aluminum ore: a mineral first discov - —Aluminum to which metallic Bauxite Alloy, aluminum ered at Les Baux, France, containing about 40- additions, known as alloying elements, have been 55% alumina (aluminum oxide ), with impurities made to impart certain properties. The most such as iron oxide, silicon oxide, titanium oxide important alloying elements for aluminum include and water. magnesium, copper, silicon, manganese and zinc. —The process, patented in 1888, —Aluminum oxide , A1 0 , an interme - Bayer process Alumina 2 3 commonly used to extract alumina from bauxite diate product extracted from bauxite and from as an intermediate stage in the production of alu - which aluminum metal is separated by the Hall- minum metal. Heroult reduction process; aluminum oxide , a very hard material, is also widely used as an abra - Belt caster —A device which casts metal directly sive. and continuously into the form of plate or sheet by allowing molten metal to solidify between —A thermal treatment to soften metal Annealing cooled traveling belts which serve as local mold by removal of stress resulting from cold working walls. or by coalescing precipitates from solid solution . See also “Full Annealing ”, “ Partial Annealing ” Bite —The initial contact friction from work rolls and “Stabilization Annealing .” which draws the material being rolled into the roll gap . Anode —A positive electrical pole: in the Hall- Heroult process , the positively-charged carbon Block caster —A device which casts metal pole which attracts and reacts with the oxygen directly in the form of plate or sheet by allowing from dissolved aluminum oxide . molten metal to solidify in contact with traveling cold blocks which serve as heat-sinks and as local —A process for artificially increasing Anodizing mold walls. the thickness of the oxide layer on aluminum by applying a direct current while the piece is sus - Breakdown mill —A rolling mill which first pended in an electrolyte. The aluminum work - reduces aluminum ingot to slab , plate or sheet piece itself serves as the electrical anode ; hence, thickness. the name “ anodizing .” Bright-dipping —Chemical treatment of alu - ANSI —American National Standards Institute; minum in a special dip solution to produce diffuse verifies industry standard-setting procedures and bright or highly specular (mirror-bright) finishes. accredits industry-adopted standards. Casting —Allowing a liquid material to solidify ANSI -H35.2 —“American National Standard inside a shaping form; a product formed by cast - Dimensional Tolerances for Aluminum Mill ing. I GLOSSARY 9-2

Cold rolling —Rolling performed on metal at a Drop —The shop term for the direct-chill casting temperature sufficiently low that strain-hardening of one or more rolling ingots in a set; that is, the (work hardening ) occurs. Cold rolling may be per - result of one lowering or “ drop ” of the hydraulic formed at room temperature or at a moderately cylinder in the casting pit. raised temperature. Ductility —The degree to which a metal or other Cold working —Plastic deformation of metal at material may be deformed without breaking, a such temperature and rate that strain hardening property important for forming during fabrication occurs. and for impact resistance in service; the opposite of brittleness. Concaved roll —A work roll made to be of slight - ly smaller diameter toward the center than toward Electromagnetic casting —Metal casting in its ends at room temperature, to compensate for which an electromagnetic field is applied to con - anticipated thermal expansion during rolling. tain molten metal and prevent it from physically touching mold walls while it solidifies; sometimes Continuous casting —Any process capable of used in conjunction with “ Direct-Chill Casting” to casting a material into a continuously elongating produce ingots with particularly smooth, uniform - form without interruptions as long as the process ly alloyed surfaces. is continued. See, also, Direct Casting. Flat rolling —A general term for the rolling of all Controlled-atmosphere annealing — flat products with uniform thickness, including Annealing carried out in a dry inert atmosphere, plate, sheet and foil . often nitrogen gas. Foil —A flat-rolled product rectangular in cross Cross rolling —Rolling ingot by feeding it into section and form of thickness ≤ 0.0079 inch the roll gap with its longest dimension parallel to (<0.20 mm). (Note: Foil was previously defined the roll axes; sometimes performed to widen the as being <0.006 inch (0.15 mm thick.)) material before rolling it to its intended thickness and length. Four-high mill —A rolling mill which employs four rolls: two work rolls , each supported by a Crowned roll —A work roll made to be of slight - backup roll . ly larger diameter toward the center than toward the ends, to compensate for anticipated roll deflection Full annealing —Annealing performed above the during rolling. recrystallization temperature for a long enough time to convert an alloy into its softest, most Cryolite —The main component and solvent of ductile, most workable condition, designated the the electrolytic bath in which aluminum oxide is “O- temper .” dissolved in the Hall-Heroult aluminum produc - tion process; a mineral containing sodium alu - Grain —A small region of solid metal within minum fluoride (Na 3AlF 6). It occurs naturally in which the atoms are arranged in a continuous Greenland, but most of the cryolite in commercial uniform “ lattice .” use is produced synthetically. “As-cast” grains form during crystallization Direct casting —In the context of plate and sheet when molten metal solidifies. production, any process in which molten metal is cast directly into a flat form, of sheet or plate “Deformed” grains , usually elongated, thickness; see also, “ Roll Casting”, “Belt Casting” are formed during hot or cold working. and “Block Casting.” Also known as “continuous “Recrystallized” grains form during casting.” annealing . —A process for cast - Direct-chill (D-C) casting Hall-Heroult reduction process —The common ing ingots by pouring molten metal into a water- commercial method of separating aluminum metal cooled mold collar whose floor is slowly with - from its oxide ( alumina ). Invented in 1886 by drawn as the metal forms a solid shell, permitting Charles Martin Hall in the United States and Paul the casting of large, elongated ingots without the L.T. Heroult in France, it is based on the principle complete enclosure of a full-sized mold. of dissolving aluminum oxide in molten cryolite I GLOSSARY 9-3

and separating the aluminum from oxygen by Partial annealing —Thermal treatment given application of electric current. cold worked metal to reduce strain-hardening to a controlled level. Heat-treating —Heating and cooling a solid metal or alloy in such a way as to obtain desired Plate —A rolled product rectangular in cross sec - conditions or properties. Commonly used as a tion and form of thickness 0.250 inch (6.3 mm) or shop term to denote a thermal treatment to more, with either sheared or sawed edges. (Note: increase strength . Heating for the sole purpose When products are ordered to metric specifica - of hot working (preheating) is excluded from the tions using metric dimensions, plate is defined meaning of this definition. (See also, “ Aging ”, as being > 6 mm thick.) “Annealing ”, “ Partial Annealing ”, “Stress Relief” and “Solution Heat Treating.” Pot —A single Hall-Heroult process “cell”: a refractory container holding alumina dissolved in Heat-treatable alloy —An alloy which may be molten cryolite , through which electric current is strengthened by a suitable thermal treatment . passed to produce aluminum metal.

Hot rolling —Rolling performed on metal at a Potline —A number of Hall-Heroult “pots” temperature high enough to avoid strain- connected in series on the same electrical circuit. hardening . Precipitation hardening —See “ Aging .” Hot working —Plastic deformation of metal at such temperature and rate that strain hardening Pre-heating —A high temperature soaking treat - does not occur. ment to provide a desired metallurgical structure in preparation for rolling. Homogenizing is a form Inclusion —Foreign material in the metal or of preheating. impressed into the surface. Pure aluminum —In common industry parlance, Ingot , rolling —A thick cast form suitable for “pure ” aluminum refers to metal which is at least rolling. 99.00 percent aluminum, as produced by standard commercial methods. Aluminum of higher purity —The application of controlled mechan - Leveling can be produced by special processes. ical force to remove edge waves, pockets or other flatness irregularities, yielding plate or sheet Quenching —Cooling of a metal from an elevat - which is essentially flat. ed temperature by contact with a liquid, a gas, or a solid. Mill finish —The general-purpose surface finish, which meets most customer needs, produced by Recrystallization —The transformation of a cold - work rolls surfaced mainly for effective thickness worked grain structure, at sufficiently high tem - reduction. peratures, into a soft metal structure with new grains. Mill, rolling —An installation consisting of a roll stand and its rolls and related equipment. Recrystallization temperature —A temperature above which the formation of new grains within a —Precipitation from solid solution Natural aging deformed structure takes place; it is dependent on at room temperature, resulting in a change in both the amount of previous cold working and on properties of an alloy. the annealing time. —An alloy which can Non-heat-treatable alloy —Aluminum of very high be strengthened only by cold work. Refined aluminum purity (99.950 percent or higher) obtained by special metallurgical treatments. Nucleation —The formation of aggregates of atoms which are stable enough to grow and form —Heating metal to hot-working tem - new grains upon heating following deformation; Reheating perature. In general no changes in metallurgical the first stage in the process of recrystallization. structure are intended by simple reheating . I GLOSSARY 9-4

Reversing mill —A rolling mill which can roll cross-section hot rolled from ingot to about four plate or sheet on both directions by reversing the inches thickness, suitable for further rolling. rotation of its rolls between passes. Soak —In metallurgy , to maintain metal at a con - Roll caster —A device which directly produces trolled elevated temperature for a sufficient time plate or sheet by pouring molten metal into the to achieve the purposes of a thermal treatment . gap between two cooled rolls where it solidifies —Heating an alloy at a before emerging as a flat product. Some hot work - Solution heat-treating suitable elevated temperature for sufficient time to ing takes place as the solidified metal is rolled allow soluble constituents to enter into solid solu - through the gap, but the product thickness is tion where they are retained in a supersaturated achieved mainly by the casting, not the rolling, state after quenching . process. —A tolerance other than —The space between work rolls which Special tolerance Roll gap “Standard.” determines the thickness of the rolled product. —Moderate-temperature —Passing a solid, ductile material between Stabilization annealing Rolling heating of certain non-heat-treatable aluminum- two work rolls to reduce its thickness and/or magnesium alloys to stabilize their cold-worked impart a desired surface finish. mechanical and dimensional properties. Rolls —The round metal cylinders used for rolling. Stand, rolling —A structure which supports and Scalping —Machining the surface of an ingot to controls a set of rolls. remove physical and/or metallurgical irregulari - —Tolerances broadly ties. Standard Tolerances accepted by the aluminum industry and users of Series, alloy —In most of the world, aluminum aluminum products as limits on acceptable devia - alloys are assigned four-digit identifying numbers tions from nominal dimensions or other parame - which group them in “series” according to their ters. Standard tolerances are routinely applied main alloying elements. Each series is identified unless non-standard tolerances are specified by by the first digit of the alloy number. For exam - agreement between supplier and purchaser. ple, the “1xxx” (or “1000”) series includes alu - Standard tolerances for aluminum rolled products minum of 99 percent or higher purity; the “2xxx” are presented in ANSI -H35.2, “American National series includes aluminum alloys in which copper Standard Dimensional Tolerances for Aluminum is the principal alloying element; and so on. Mill Products”, and in “Aluminum Standards and The alloy series are explained in “Aluminum Data”, both published by The Aluminum Standards and Data”, published by The Aluminum Association. (See also Technical Appendix D.) Association. Other alloy identification systems —A measure of the change in size or shape may be used in some other countries. (See also, Strain of a body under stress, referred to its original size Technical Appendix A.) or shape. —A rolled product rectangular in cross Sheet —Modification of a metal section and form of thickness >0.0079 inch Strain-hardening structure by cold working resulting in an increase (over 0.20 mm) through 0.249 inch (6.3 mm), with in strength and hardness with a corresponding loss sheared, slit or sawed edges. (Notes: When products of ductility . are ordered to metric specifications using metric dimensions, sheet is defined as being > 0.20 mm Stress —Force per unit of area. to ≤ 6 mm thick. Sheet was previously defined as being .006 to .249 inch (.15 to 6.3 mm) in thick - Stress relief —The reduction, by thermal or ness.) mechanical means, of internal residual stresses. —Flattening sheet or plate by Single-stand mill —A rolling mill with only one Stretcher- leveling “stand” of rolls. mechanically gripping its ends and applying a controlled amount of stretching. Slab —A semifinished product of rectangular Strip —Continuous sheet. I GLOSSARY 9-5

Table rolls —motor-driven horizontal rollers which position an aluminum ingot or slab and transport it to a mill’s work rolls .

Tandem mill —Multiple rolling stands arranged in sequence and coordinated to apply successive thickness reductions to aluminum sheet during a single pass through.

Temper —The combination of mechanical proper - ties, particularly strength , hardness and ductility , induced in a metal product by the thermal and/or mechanical treatments applied during its prepara - tion.

Tension leveling —Flattening sheet by controlled flexing: usually by passing it in tension over an adjustable roll .

Thermal treatment —A very general term mean - ing any treatment in which heat is applied, usually to alter the mechanical properties of solid metal; it includes homogenizing or precipitation treatment of ingots to affect finished grain size or some other property.

Tolerance —Allowable deviation from a nominal or specified dimension or other parameter: the maximum deviation that may be expected in any individual piece.

Two-high mill —A rolling mill employing only its two work rolls .

Ultrasonic inspection —The non-destructive testing of rolled plate (or other products) by trans - mitting ultrasonic sound waves (frequencies above human hearing) through the tested product. Electronic comparison of the time differences between reflected waves can reveal internal flaws.

Work-harden —See “Strain-harden.” Work rolls —In a rolling mill, the metal cylinders which grip the product, roll it between them and reduce its thickness.

Work —In metallurgy , to deform metal sufficient - ly to alter its metallurgical structure and conse - quently its mechanical properties.

Wrought product —A product which has been subjected to mechanical working. Rolling produces wro ught products. I GLOSSARY 9-6

NOTES I GLOSSARY 9-7

SELF-TEST QUESTIONS 9.6 In rolling, “ mill finish ” is… a. the final condition of all rolled prod - SECTION 9: GLOSSARY ucts. b. a general-purpose surface that meets 9.1 An anode is… most needs. a. a negative electrical pole. c. a special surface finish requiring extra b. a positive electric pole. steps. c. a type of natural mineral formation. d. rolling by a five-stand tandem mill . d. an alloy which has been annealed. 9.7 “Strain” means… 9.2 In aluminum rolling, “ bite ” means… a. amount of force applied. a. the clamping action of a stretcher - b. percentage of thickness reduction. leveler. c. percentage of elongation. b. the cutting action of a slitter. d. amount of change in shape per unit c. the action of work rolls pulling metal of stress. into the roll gap . d. the amount of thickness reduction 9.8 “Stress” means… applied by a single mill stand . a. total amount of force applied. b. maximum force applied at any point. 9.3 “Controlled-atmosphere” annealing c. force applied per unit of area. means carrying out the process… d. force applied in tension. a. in a filtered natural-air atmosphere. e. twisting force. b. in an oxygen-rich atmosphere. c. in a corrosive-gas atmosphere. 9.9 “Wrought” aluminum means a product d. in an inert-gas atmosphere. which has been… a. cast under high pressure. 9.4 “Ductility ” means, roughly… b. solution heat treated and quenched. a. tensile strength . c. annealed in a controlled atmosphere. b. ease of deformation. d. subjected to mechanical working. c. corrosion resistance . e. none of the above. d. scratch-resistance.

9.5 In metallurgy , “ grain ” means… a. a hard particle trapped in an alloy. b. a rough pattern produced by improper rolling. c. a small region of uniform crystalline structure. d. a speck of metal that sticks to a work roll . I GLOSSARY 9-8 I GLOSSARY 9-9 I GLOSSARY 9-10 Rolling Aluminum: From the Mine through the Mill 10 Appendix A: Alloy and Temper Designation System Alloy and Temper Designation Systems for Aluminum ( ANSI H35.1-2006)

mined by the alloying element (Mg Si for 6xxx 1. Scope 2 This standard provides systems for designating alloys ) present in the greatest mean percentage, wrought aluminum and wrought aluminum alloys , except in cases in which the alloy being registered aluminum and aluminum alloys in the form of cast qualifi es as a modification or national variation of ings and foundry ingot , and the tempers in which a previously registered alloy. If the greatest mean aluminum and aluminum alloy wrought products and percentage is common to more than one alloying aluminum alloy castings are pro duced. Specific lim - element, choice of group will be in order of group its for chemical compositions and for mechanical and sequence Cu, Mn, Si, Mg, Mg 2Si, Zn or others. physical properties to which conformance is required The last two digits identify the aluminum alloy or are provided by applicable product standards. indicate the aluminum purity. The second digit indi NOTE: A numerical designation assigned in con - cates modifications of the original alloy or impurity formance with this stan dard should only be used to limits. indicate an aluminum or an aluminum alloy having chemical composition limits identical to those regis - tered with The Aluminum Association and, for wrought aluminum and wrought aluminum alloys , with the signatories of the Declaration of Accord 1 Chemical composition limits and designations conforming to this standard for wrought aluminum and wrought aluminum alloys , and aluminum and on an International Alloy Designation System for aluminum alloy castings and foundry ingot may be registered with The 1 Aluminum Association provided: (1) the aluminum or aluminum alloy is offered Wrought Aluminum and Wrought Aluminum Alloys . for sale, (2) the complete chemical composition limits are registered, and (3) the composition is signifi cantly different from that of any aluminum or aluminum alloy for which a numerical designation already has been assigned. 2. Wrought Aluminum and Aluminum 2 For codification purposes an alloying element is any element that is inten - 1 tionally added for any purpose other than grain refi nement and for which Alloy Designation System minimum and maximum limits are specifi ed. A system of four-digit numerical designations is 3 Standard limits for alloying elements and impurities are expressed to the following places: used to identify wrought aluminum and wrought Less than .001 percent ...... 0.000X aluminum alloys . The first digit indicates the alloy .001 but less than .01 percent ...... 0.00X .01 but less than .10 percent group as follows: Unalloyed aluminum made by a refi ning process . . . . . 0.0XX Alloys and unalloyed aluminum not made by a Aluminum, 99.00 percent and greater ...... 1xxx refining process ...... 0.0X Aluminum alloys grouped by .10 through .55 percent ...... 0.XX 2 3 4 (It is customary to express limits of 0.30 percent through 0.55 percent as 0.X0 or major alloying elements 0.X5) Copper ...... 2xxx Over .55 percent 0.X, X.X, etc. Manganese ...... 3xxx (except that combined Si + Fe limits for 1xxx designations must be expressed as 0.XX or 1.XX) Silicon ...... 4xxx 4 Standard limits for alloying elements and impurities are expressed in the fol - Magnesium ...... 5xxx lowing sequence: Silicon; Iron; Copper; Manganese; Magnesium; Chromium; Magnesium and silicon ...... 6xxx Nickel; Zinc; Titanium (see Note 1); Other (see Note 2) Elements, Each; Other (see Note 2) Elements, Total; Aluminum (see Note 3). Zinc ...... 7xxx Note 1—Additional specifi ed elements having limits are inserted in alphabeti - Other element ...... 8xxx cal order according to their chemical symbols between Titanium and Other Unused series ...... 9xxx Elements, Each, or are listed in footnotes. Note 2—“Other” includes listed elements for which no specifi c limit is shown as well as unlisted metallic elements. The producer may analyze samples for trace elements not specifi ed in the registration or specification. However, The designation assigned shall be in the 1xxx such analysis is not required and may not cover all metallic “other” elements. Should any analysis by the producer or the purchaser establish that an “other” group whenever the minimum aluminum content is element exceeds the limit of “Each” or that the aggregate of several “other” specified as 99.00 percent or higher. The alloy desig - elements exceeds the limit of “Total”, the material shall be considered non- conforming.Note 3—Aluminum is specifi ed as minimum for unalloyed alu - nation in the 2xxx through 8xxx groups is deter - minum, and as a remainder for aluminum alloys . I APPENDIX A 10A-2

To determine compliance when maximum and mini - 2.1 Aluminum mum limits are specifi ed for a combination of two In the 1xxx group for minimum aluminum purities or more elements in one alloy composition, the arith - of 99.00 percent and greater, the last two of the four metic mean of such a combination is compared to the digits in the designation indicate the minimum alu - sum of the mean values of the same individual ele - minumpercentage. 5 These digits are the same as the ments, or any combination thereof, in another alloy two digits to the right of the decimal point in the composition. minimum aluminum percentage when it is expressed to the nearest 0.01 perce nt. The second digit in the (b) Addition or deletion of not more than one alloy - designation indicates modifications in impurity limits ing element with limits having an arithmetic mean or alloying elements. If the second digit in the designa - of not more than 0.30 percent or addition or deletion tion is zero, it indicates unalloyed aluminum having of not more than one combination of elements natural impurity limits; integers 1 through 9, which are expressed as an alloying element with limits having assigned con secutively as needed, indicate special a combined arithmetic mean of not more than 0.40 control of one or more individual impurities or alloy - percent. ing ele ments. (c) Substitution of one alloying element for another 2.2 Aluminum Alloys element serving the same purpose. In the 2xxx through 8xxx alloy groups the last two of (d) Change in limits for impurities expressed singly the four digits in the designation have no special sig - or as a combination. nificance but serve only to identify the different alu minum alloys in the group. The second digit in the (e) Change in limits for grain refi ning elements. alloy designation indicates alloy modifications. If the (f ) Maximum iron or silicon limits of 0.12 percent second digit in the designation is zero, it indicates the and 0.10 percent, or less, respectively, reflecting use original alloy; integers 1 through 9, which are as of high purity base metal. signed consecutively, indicate alloy modifications. A modification of the original alloy is limited to any An alloy shall not be registered as a modification if it one or a combination of the following: meets the requirements for a nat ional variation. (a) Change of not more than the following amounts in arithmetic mean of the limits for an individual 2.3 Experimental Alloys alloying element or combination of elements Experimental alloys are also designated in accor - expressed as an alloying element or both. dance with this system, but they are indicated by the prefix X. The prefix is dropped when the alloy is no Arithmetic Mean of longer experimental. Limits for Alloying Maximum Elements in Original Alloy Change During development and before they are designated Up thru 1.0 percent ...... 0.15 as experimental, new alloys are identifi ed by serial Over 1.0 thru 2.0 percent ...... 0.20 numbers assigned by their originators. Use of the Over 2.0 thru 3.0 percent ...... 0.25 serial number is discontinued when the X number Over 3.0 thru 4.0 percent ...... 0.30 is assigned. Over 4.0 thru 5.0 percent ...... 0.35 Over 5.0 thru 6.0 percent ...... 0.40 2.4 National Variations Over 6.0 percent ...... 0.50 National variations of wrought aluminum and

5 The aluminum content for unalloyed aluminum made by a refining process wrought aluminum alloys registered by another coun is the difference between 100.00 percent and the sum of all other metallic try in accordance with this system are identified by a elements plus silicon present in amounts of 0.0010 percent or more, each expressed to the third decimal before determining the sum, which is round - serial letter following the numerical designation. The ed to the second decimal before subtracting; for unalloyed aluminum not made by a refi ning process it is the difference between 100.00 percent and serial letters are assigned internationally in alphabet the sum of all other analyzed metallic elements plus silicon present in amounts of 0.010 percent or more, each expressed to the second decimal ical sequence starting with A but omitting I, O and Q. before determining the sum. For unalloyed aluminum made by a refi ning process, when the specifi ed maximum limit is 0.0XX, an observed value or a A national variation has composition limits that are calculated value greater than 0.0005 but less than 0.0010% is rounded off and shown as “less than 0.001”; for alloys and unalloyed aluminum not similar but not identical to those registered by an made by a refi ning process, when the specifi ed maximum limit is 0.XX, an observed value or a calculated value greater than 0.005 but less than other country, with differences such as: 0.010% is rounded off and shown as “less than 0.01”. I APPENDIX A 10A-3

(a) Change of not more than the following amounts Aluminum, 99.00 percent minimum and greater . . . 1xx.x in arithmetic mean of the limits for an individual Aluminum alloys grouped by major alloying element or combination of elements alloying elements 2 3 4 expressed as an alloying element, or both: Copper ...... 2xx.x Silicon, with added copper and/or magnesium . 3xx.x Silicon ...... 4xx.x Arithmetic Mean of Magnesium ...... 5xx.x Limits for Alloying Zinc ...... 7xx.x Elements in Original Maximum Tin ...... 8xx.x Alloy or Modification Change Other element...... 9xx.x Unused series ...... 6xx.x Up thru 1.0 percent ...... 0.15 Up thru 1.0 percent...... 0.15 The alloy group in the 2xx.x through 9xx.x exclud - Over 1.0 thru 2.0 percent ...... 0.20 ing 6xx.x alloys is determined by the alloying ele - ment present in the greatest mean percentage, except Over 2.0 thru 3.0 percent ...... 0.25 in cases in which the alloy being registered qualifi Over 3.0 thru 4.0 percent ...... 0.30 ed as a modifi cation of a previously registered Over 4.0 thru 5.0 percent ...... 0.35 alloy. If the greatest mean percentage is common to Over 5.0 thru 6.0 percent ...... 0.40 more than one alloying element, the alloy group will Over 6.0 percent ...... 0.50 be deter mined by the sequence shown above. To determine compliance when maximum and mini - The second two digits identify the aluminum alloy mum limits are specifi ed for a combination of two or indicate the aluminum purity. The last digit, or more elements in one alloy composition, the which is separated from the others by a decimal arithmetic mean of such a combination is compared point, indicates the product form: that is, castings or to the sum of the mean values of the same individual ingot . A modification of the original alloy or impuri - elements, or any combination thereof, in another ty limits is indicated by a serial letter before the alloy compo sition. numerical designation. The serial letters are assigned (b) Substitution of one alloying element for another in alphabet ical sequence starting with A but omit - element serving the same purpose. ting I, O, Q and X, the X being reserved for experi mental alloys . (c) Different limits on impurities except for low iron. Iron maximum of 0.12 percent, or less, reflecting A modification of the original alloy is limited to any high purity base metal, should be considered as an one or a combination of the following: alloy modification. (a) Change of not more than the following amounts (d) Different limits on grain refining elements. in the arithmetic mean of the limits for an individual alloying element or combination of elements (e) Inclusion of a minimum limit for iron or silicon, expressed as an alloying element or both: or both. Wrought aluminum and wrought aluminum alloys Arithmetic Mean of meeting these requirements shall not be registered as Limits for Alloying Maximum a new alloy or alloy modification. Elements in Original Alloy Change Up thru 1.0 percent ...... 0.15 3. Cast Aluminum and Aluminum Over 1.0 thru 2.0 percent ...... 0.20 1 Over 2.0 thru 3.0 percent ...... 0.25 Alloy Designation System Over 3.0 thru 4.0 percent ...... 0.30 A system of four digit numerical designations is Over 4.0 thru 5.0 percent ...... 0.35 used to identify aluminum and aluminum alloys in Over 5.0 thru 6.0 percent ...... 0.40 the form of castings and foundry ingot . The first Over 6.0 percent ...... 0.50 digit indicates the alloy group as follows: To determine compliance when maximum and mini mum limits are specifi ed for a combination of two or more elements in one alloy composition, the arithmetic mean of such a combination is compared I APPENDIX A 10A-4

to the sum of the mean values of the same individual 3.2.1 Limits for alloying elements and impurities elements, or any combination thereof, in another for xxx.1 ingot are the same as for the alloy in the alloy composition. form of castings, except for the following: (b) Addition or deletion of not more than one alloy - Maximum Iron Percentage: ing element with limits having an arithmetic mean For Sand and Permanent of not more than 0.30 percent or addition or deletion Mold Castings For Ingot of not more than one combination of elements Up thru 0.15 ...... 0.03 less than castings expressed as an alloying element with limits having Over 0.15 thru 0.25 . . . . . 0.05 less than castings a combined arithmetic mean of not more than 0.40 Over 0.25 thru 0.6 ...... 0.10 less than castings per cent. Over 0.6 thru 1.0 ...... 0.2 less than castings (c) Substitution of one alloying element for another Over 1.0 ...... 0.3 less than castings element serving the same purpose. For Die Castings For Ingot (d) Change in limits for impurities expressed singly Up thru 1.3 ...... 0.3 less than castings or as a combination. Over 1.3 ...... 1.1 maximum (e) Change in limits for grain refining elements. Minimum Magnesium Percentage: For All Castings For Ingot (f ) Iron or silicon maximum limits of 0.12 percent Less than 0.50 ...... 0.05 more than castings* and 0.10 percent, or less, respectively, reflecting use 0.50 and greater ...... 0.1 more than castings* of high purity base metal. Maximum Zinc Percentage: For Die Castings For Ingot 3.1 Aluminum Castings and Ingot Over 0.25 thru 0.6 ...... 0.10 less than castings In the 1xx.x group for minimum aluminum purities Over 0.6 ...... 0.1 less than castings of 99.00 percent and greater, the second two of the *Applicable only if the resulting magnesium range is 0.15 percent or four digits in the designation indicate the minimum greater. aluminum percentage. 5 These digits are the same as the two digits to the right of the decimal point in the 3.3 Experimental Alloys minimum aluminum percentage when it is expressed Experimental alloys are also designated in accor to the nearest 0.01 percent. The last digit, which is to dance with this system, but they are indicated by the the right of the decimal point, indicates the product prefix X. The prefix is dropped when the alloy is no form: 1xx.0 indicates castings, and 1xx.1 indicates longer experimental. ingot . During development and before they are designat - ed as experimental, new alloys are identified by seri - 3.2 Aluminum Alloy Castings and Ingot al numbers assigned by their originators. Use of the In the 2xx.x through 9xx.x alloy groups the second serial number is discontinued when the X number is two of the four digits in the designation have no spe assigned. cial significance but serve only to identify the differ - ent aluminum alloys in the group. The last digit, which is to the right of the decimal point, indicates the product form: xxx.0 indicates castings, xxx.1 indicates ingot that has chemical composition limits conforming to 3.2.1, and xxx.2 indicates ingot that has chemical composition limits that differ but fall within the limits of xxx.1 ingot . I APPENDIX A 10A-5 I APPENDIX A 10A-6 Rolling Aluminum: From the Mine through the Mill 10 Appendix B Aluminum Temper Designation System

6 applicable only to alloys that spontaneously age 4. Temper Designation System at room temperature after solution heat- The temper designation system is used for all forms treatment . This designation is specific only when of wrought and cast aluminum and aluminum alloys the period of natural aging is indicated; for except ingot . It is based on the sequences of basic example: W 1/2 hr. treatments used to produce the various tempers. The temper designation follows the alloy designation, the T thermally treated to produce stable two being separated by a hyphen. Basic temper desig - tempers other than F, O, or H. Applies to nations consist of letters. Subdivisions of the basic products that are thermally treated, with or without tempers, where required, are indicated by one or more supplementary strain-hardening , to produce stable digits following the letter. These designate specific tempers. The T is always followed by one or sequences of basic treatments, but only operations more digits. recognized as significantly influencing the character - istics of the product are indicated. Should some other 4.2 Subdivisions of Basic Tempers variation of the same sequence of basic operations be applied to the same alloy, resulting in different char - 4.2.1 Subdivision of H Temper : Strain- acteristics, then additional digits are added to the hardened designation. 4.2.1.1 The first digit following the H indi - cates the specific combination of basic 4.1 Basic Temper Designations operations, as follows: Applies to the products of shap - F as fabricated. H1 strain-hardened only. Applies to products ing processes in which no special control over that are strain-hardened to obtain the desired thermal conditions or strain hardening is strength without supplementary thermal treat - employed. For wrought products, there are no ment . The number following this designation mechanical property limits. indicates the degree of strain-hardening . Applies to wrought products that are O annealed. H2 strain-hardened and partially annealed. annealed to obtain the lowest strength temper , Applies to products that are strain-hardened more and to cast products that are annealed to improve than the desired final amount and then reduced in ductility and dimensional stability. The O may be strength to the desired level by partial annealing . followed by a digit other than zero. For alloys that age-soften at room temperature, the H2 tempers have the same minimum ultimate H strain-hardened (wrought products only). Applies to products that have their strength tensile strength as the corresponding H3 tempers. increased by strain-hardening , with or without For other alloys , the H2 tempers have the same supplementary thermal treatments to produce minimum ultimate tensile strength as the corre - some reduction in strength . The H is always sponding H1 tempers and slightly higher elonga - followed by two or more digits. tion. The number following this designation indi - cates the degree of strain-hardening remaining W solution heat-treated. An unstable temper after the product has been partially annealed.

6 Temper designations conforming to this standard for wrought aluminum H3 strain-hardened and stabilized. Applies and wrought aluminum alloys , and aluminum alloy castings may be regis - tered with the Aluminum Association provided: (1) the temper is used or is to products that are strain-hardened and whose avail able for use by more than one user, (2) mechanical property limits are mechanical properties are stabilized either by a regis tered, (3) the characteristics of the temper are significantly different from those of all other tempers that have the same sequence of basic treat - low temperature thermal treatment or as a result ments and for which designations already have been assigned for the same alloy and product, and (4) the following are also registered if characteristics of heat introduced during fabrication. other than mechanical properties are considered significant: (a) test meth - Stabilization usually improves ductility . This ods and limits for the characteristics or (b) the specific practices used to pro - duce the temper . I APPENDIX B 10B-2

designation is applicable only to those alloys Metric Units that, unless stabilized, gradually age-soften at Minimum tensile strength Increase in tensile strength room temperature. The number following this in annealed temper to HX8 temper designation indicates the degree of strainhardening MPa MPa remaining after the stabilization treatment. up to 40 55 45 to 60 65 H4 strain-hardened and lacquered or paint - 65 to 80 75 ed. Applies to products which are strain-hard - 85 to 100 85 ened and which are subjected to some thermal 105 to 120 90 operation during the subsequent painting or lac - 125 to 160 95 quering operation. The number following this 165 to 200 100 designation indicates the degree of strain-harden - 205 to 240 105 ing remaining after the product has been thermal - 245 to 280 110 ly treated, as part of painting/lacquering cure 285 to 320 115 operation. The corresponding H2X or H3X 325 and over 120 mechanical property limits apply. Tempers between O (annealed) and HX8 are desig - The digit following the designation H1, H2, 4.2.1.2 nated by numerals 1 through 7. H3, and H4 indicates the degree of strain-hardening as identified by the minimum value of the ultimate —Numeral 4 designates tempers whose ultimate tensile strength . Numeral 8 has been assigned to the tensile strength is approximately midway hardest tempers normally produced. The minimum between that of the O temper and that of the tensile strength of tempers HX8 may be determined HX8 tempers; from Table 1 and is based on the minimum tensile —Numeral 2 designates tempers whose ultimate strength of the alloy in the annealed temper . tensile strength is approximately midway However, temper registrations prior to 1992 that do between that of the O temper and that of the not conform to the requirements of Table 1 shall not HX4 tempers; be revised and registrations of intermediate or modi - fied tempers for such alloy/ temper systems shall —Numeral 6 designates tempers whose ultimate conform to the registration requirements that existed tensile strength is approximately midway prior to 1992. between that of the HX4 tempers and that of the HX8 tempers; Table 1 —Numerals 1, 3, 5 and 7 designate, similarly, US Customary Units tempers intermediate between those defined Minimum tensile strength Increase in tensile strength above. in annealed temper to HX8 temper ksi ksi —Numeral 9 designates tempers whose mini - up to 6 8 mum ultimate tensile strength exceeds that of the 7 to 9 9 HX8 tempers by 2 ksi or more. (For Metric Units 10 to 12 10 by 10 MPa or more). 13 to 15 11 16 to 18 12 The ultimate tensile strength of the odd numbered 19 to 24 13 intermediate (-HX1, -HX3, -HX5, and HX7) tem - 25 to 30 14 pers, determined as described above, shall be round - 31 to 36 15 ed to the nearest multiple of 0.5 ksi. (For Metric 37 to 42 16 Units when not ending in 0 or 5, shall be rounded to 43 and over 17 the next higher 0 or 5 MPa.)

7 4.2.1.3 The third digit, when used, indicates a vari - ation of a two-digit temper . It is used when the de gree of control of temper or the mechanical proper ties or both differ from, but are close to, that (or those) for the two-digit H temper designation to I APPENDIX B 10B-3

which it is added, or when some other characteristic ture shaping process, or in which the effect of is signifi cantly affected. (See Appendix for assigned cold work in flattening or straightening may not three-digit H tempers.) NOTE: The minimum ulti - be recognized in mechanical property limits. mate tensile strength of a three-digit H temper must 9 and then artificially be at least as close to that of the corresponding two- T6 solution heat-treated aged. Applies to products that are not cold digit H temper as it is to the adjacent two-digit H worked after solution heat-treatment , or in which tempers. Products in the H temper whose mechani - the effect of cold work in flattening or straight - cal properties are below H__1 shall be variations of ening may not be recognized in mechanical H__1. property limits.

T7 solution heat-treated 9 and overaged/stabi - 4.2.2 Subdivision of T Temper : lized. Applies to wrought products that are artifi Thermally Treated cially aged after solution heat treatment to carry 4.2.2.1 Numerals 1 through 10 following the T them beyond a point of maximum strength to indicate specific sequences of basic treatments, provide control of some significant as follows: 8 characteristic 10 . Applies to cast products that are artifi cially aged after solution heat-treatment to T1 cooled from an elevated temperature provide dimensional and strength stability. shaping process and nat urally aged to 9 a substantially stable condition. Applies to T8 solution heat-treated, cold worked, and prod ucts that are not cold worked after cooling then artificially aged. Applies to products from an elevated temperature shaping process, or that are cold worked to improve strength , or in in which the effect of cold work in flattening or which the effect of cold work in flattening or straightening may not be recognized in mechani - straightening is recognized in mechanical prop - cal property limits. erty limits.

9 T2 cooled from an elevated temperature T9 solution heat-treated, artificially aged, shaping process, cold worked, and nat - and then cold worked. Applies to products urally aged to a substantially stable con - that are cold worked to improve strength . dition. Applies to products that are cold worked to improve strength after cooling from an elevat - T10 cooled from an elevated tempera ture ed temperature shaping process, or in which the shaping process, cold worked, and then Applies to products that are effect of cold work in flattening or straightening artificially aged. cold worked to improve strength , or in which the is recognized in mechanical property limits. effect of cold work in flattening or straightening T3 solution heat-treated, 9 cold worked, and is recognized in mechanical property limits. naturally aged to a substantially stable condition. Applies to products that are cold worked to improve strength after solution heat- treatment , or in which the effect of cold work in flattening or straightening is recognized in 7 Numerals 1 through 9 may be arbitrarily assigned as the third digit and reg - mechanical property limits. istered with the Aluminum Association for an alloy and product to indicate a variation of a two-digit H temper (see note Y). 9 T4 solution heat-treated and naturally aged 8 A period of natural aging at room temperature may occur between or to a substantially stable condition. Applies after the operations listed for the T tempers. Control of this period is exercised to products that are not cold worked after solu - when it is metallurgically important. tion heat-treatment , or in which the effect of cold 9 Solution heat treatment is achieved by heating cast or wrought products to a suitable temperature, holding at that temperature long enough to allow work in flattening or straightening may not be constituents to enter into solid solution and cooling rapidly enough to hold the con stituents in solution. Some 6xxx series alloys attain the same specified recognized in mechanical property limits. mechanical properties whether furnace solution heat treated or cooled from an elevated temperature shaping process at a rate rapid enough to hold con stituents in solution. In such cases the temper designa tions T3, T4, T6, T7, T5 cooled from an elevated temperature T8, and T9 are used to apply to either process and are appropriate designa - shaping process and then artificially tions. Applies to products that are not cold aged. 10 For this purpose, characteristic is something other than mechanical prop - worked after cooling from an elevated tempera - erties. The test method and limit used to evaluate material for this character - istic are specifi ed at the time of the temper registration I APPENDIX B 10B-4

11 4.2.2.2 Additional digits, the first of which shall A1.3 The following three-digit H temper designa - not be zero, may be added to designations T1 tions have been assigned only for wrought prod - through T10 to indicate a variation in treatment ucts in the 5xxx series, for which the magnesium that significantly alters the product characteristics content is 3% nominal or more: that are or would be obtained using the basic H116 Applies to products manufactured from alloys treatment. (See Appendix for specific additional in the 5xxx series, for which the magnesium digits for T tempers.) content is 3% nominal or more. Products are strain hardened at the last operation to specifi ed stable tensile property limits and meet 4.3 Variations of O Temper : Annealed specified levels of corrosion resistance in accelerated type corrosion tests. They are suit - 4.3.1 A digit following the O, when used, indi - cates a product in the annealed condition having able for continuous service at temperature no greater than 150°F (66°C). Corrosion tests special characteristics. include inter-granular and exfoliation. NOTE: As the O temper is not part of the strain- H321 Applies to products from alloys in the 5xxx hardened (H) series, variations of O temper shall series, for which the magnesium content is 3% not apply to products that are strain-hardened after nominal or more. Products are thermally stabi - annealing and in which the effect of strain-harden - lized at the last operation to specified stable ing is recognized in the mechanical properties or tensile property limits and meet specified lev - other characteristics. els of corrosion resistance in accelerated type corrosion tests. They are suitable for continu - ous service at temperatures no greater than 150°F (66°C). Corrosion tests include inter- A1 Three-Digit H Tempers granular and exfoliation. A1.1 The following three-digit H temper designa - tions have been assigned for wrought products in all alloys : A2 Additional Digits for T Tempers Applies to products that incur sufficient strain H_11 A2.1 The following specific additional digits have hardening after the final anneal that they fail been assigned for stress-relieved tempers of to qualify as annealed but not so much or so consistent an amount of strain hardening that wrought products: they qualify as H_1. Stress relieved by stretching. Applies to plate and rolled or cold-finished H112 Applies to products that may acquire some T_51 temper from working at an elevated tempera - rod or bar, die or ring forgings and rolled rings ture and for which there are mechanical prop - when stretched the indicated amounts after erty limits. solution heat treatment or after cooling from an elevated temperature shaping process. The products receive no further straightening after A1.2 The following three-digit H temper designa - tions have been assigned for stretching. Plate ...... 1.5% to 3% permanent set. pattern or Rolled or embossed sheet fabricated from H114 O temper Cold-Finished H124, H224, H324 H11, H21, H31 temper , respectively Rod and Bar ...... 1% to 3% permanent set. H134, H234, H334 H12, H22, H32 temper , respectively Die or Ring H144, H244, H344 H13, H23, H33 temper , respectively Forgings and H154, H254, H354 H14, H24, H34 temper , respectively Rolled Rings ...... 1% to 5% permanent set. H164, H264, H364 H15, H25, H35 temper , respectively H174, H274, H374 H16, H26, H36 temper , respectively Applies to extruded rod, bar, profiles (shapes) H184, H284, H384 H17, H27, H37 temper , respectively T_510 H194, H294, H394 H18, H28, H38 temper , respectively and tube and to drawn tube when stretched the H195, H295, H395 H19, H29, H39 temper , respectively indicated amounts after solution heat treatment or after cooling from an elevated temperature shaping process. These products receive no fur - ther straightening after stretching. Extruded Rod 11 Additional digits may be arbitrarily assigned and registered with The Aluminum Association for an alloy and product to indicate a variation of Bar, Profiles (Shapes) tempers T1 through T10 even though the temper representing the basic treat - and Tube ...... 1% to 3% permanent set. ment has not been registered (see note 6). Variations in treatment that do not alter the characteristics of the product are considered alternate treat - Drawn Tube . . . . . 1/2% to 3% permanent set. ments for which additional digits are not assigned. I APPENDIX B 10B-5

T_511 Applies to extruded rod, bar, profiles (shapes) and tube and to drawn tube when stretched the A2.3 Temper Designations for indicated amounts after solution heat treat - Producer/Supplier Demonstration of ment or after cooling from an elevated tem - Response to Temper Conversion: perature shaping process. These products may receive minor straightening after stretching to Temper designation T2 shall be used to indicate comply with standard tolerances . wrought product test material, which has under - Extruded Rod, gone furnace heat-treatment for capability demon - Bar, Profiles (Shapes) stration of temper conversion. When the purchaser and Tube ...... 1% to 3% permanent set. requires capability demonstrations from T- temper , Drawn Tube . . . . . 1/2% to 3% permanent set. the seller shall note “Capabilitiy Demonstration” adjacent to the specified and ending tempers. Stress relieved by compressing. Some examples are: T_52 Applies to products that are stress-relieved by com pressing after solution heat treatment or • “-T3 to -T82 Capability Demonstration for cooling from an elevated temperature shaping response to aging ”; process to produce a per manent set of 1 per - cent to 5 percent. • “-T4 to -T62 Capability Demonstration for response to aging ”; Stress relieved by combined stretching and compressing. • “-T4 to -T762 Capability Demonstration for response to overaging”; T_54 Applies to die forgings that are stress relieved by restriking cold in the finish die. • “-T6 to -T732 Capability Demonstration for NOTE: The same digits (51, 510, 511, 52, 54) may be response to overaging”; added to the designation W to indicate unsta - ble solution heat-treated and stress-relieved • “-T351 to -T42 Capability Demonstration for tempers. response to re-solution heat-treatment ”.

A2.2 Temper Designations for A2.4 Temper Designation for Producer/Supplier Laboratory Purchaser/User Heat-treatment Demonstration of Response to Temper designation T2 should also be applied to Heat-treatment : wrought products heat-treated by the purchaser/ The following temper designations have been as user, in accordance with the applicable heat signed for wrought products test material, furnace treatment specification, to achieve the properties heat-treated from annealed (O, O1, etc.) or F tem - applicable to the final temper . per , to demonstrate response to heat-treatment .

T42 Solution heat-treated from annealed or F A3 Assigned O Temper Variations temper and naturally aged to a substantial - A3.1 The following temper designation has been ly stable condition. assigned for wrought products high temperature annealed to accentuate ultrasonic response and T62 Solution heat-treated from annealed or F temper and artificially aged. provide dimensional stability. Thermally treated at approximately same time T7_2 Solution heat-treated from annealed or F O1 temper and artificially overaged to meet and temperature required for solution heat treatment the mechanical properties and corrosion and slow cooled to room temperature. Applicable resistance limits of the T7_ temper . to products that are to be machined prior to solution heat treatment by the user. Mechanical property limits are not applicable. I APPENDIX B 10B-6

A4 Designation of Unregistered Tempers A4.1 The letter P has been assigned to denote H, T and O temper variations that are negotiated between manufacturer and purchaser. The letter P immediately follows the temper designation that most nearly pertains. Specific examples where such designation may be applied include the fol - lowing:

A4.1.1 The use of the temper is sufficiently limit - ed so as to preclude its registration. (Negotiated H temper variations were formerly indicated by the third digit zero.)

A4.1.2 The test conditions (sampling location, number of samples, test specimen configuration, etc.) are different from those required for registra - tion with The Aluminum Association.

A4.1.3 The mechanical property limits are not established on the same basis as required for reg - istration with The Aluminum Association.

A4.1.4 For products such as Aluminum Metal Matrix Composites which are not included in any registration records. I APPENDIX A 10B-7 I APPENDIX A 10B-8 Rolling Aluminum: From the Mine through the Mill 10 Appendix C: Typical Aluminum Alloy Properties

tion begins. After a period of several days at room Metallurgical Aspects temperature, termed aging or room-temperature In high-purity form aluminum is soft and ductile. precipita tion, the alloy is considerably stronger. Most commercial uses, however, require greater Many alloys approach a stable condition at room strength than pure aluminum affords. This is temperature, but some alloys , particularly those achieved in aluminum first by the addition of containing magnesium and silicon or magnesium other elements to produce various alloys , which and zinc, continue to age-harden for long periods singly or in combination impart strength to the of time at room temperature. metal. Further strength ening is possible by means that classify the alloys roughly into two cate - By heating for a controlled time at slightly elevat - gories, non-heattreatable and heat-treatable. ed temperatures, even further strengthening is pos - sible and properties are stabilized. This process is Non- heat-treatable alloys —The initial called artificial aging or precipitation hardening . strength of alloys in this group depends upon the By the proper combina tion of solution heat treat - hardening effect of elements such as manganese, ment , quenching , cold working and artificial silicon, iron and mag nesium, singly or in various aging , the highest strengths are obtained. combinations. The non- heat-treatable alloys are usually designated, there fore, in the 1xxx, 3xxx, Clad alloys —The heat-treatable alloys in which 4xxx, or 5xxx series. Since these alloys are work- copper or zinc are major alloying constituents are hard enable, further strength ening is made possi - less resistant to corrosive attack than the majority ble by various degrees of cold working, denoted of non- heat-treatable alloys . To increase the corro - by the “H” series of tempers. Alloys containing sion resis tance of these alloys in sheet and plate appreciable amounts of magnesium when supplied form, they are often clad with highpurity alu - in strain-hardened tempers are usually given a minum, a low magnesium-silicon alloy, or an final elevated-temperature treatment called stabi - alloy containing 1 percent zinc. The cladding, lizing to ensure stability of properties. usually from 2.5 percent to 5 percent of the total thickness on each side, not only protects the com - Heat-treatable alloys —The initial strength of posite due to its own inherently excellent corro - alloys in this group is enhanced by the addition sion resistance but also exerts a galvanic effect, of alloying elements such as copper, magnesium, which further protects the core material. zinc, and silicon. Since these elements singly or in various combinations show increasing solid solu - Special composites may be obtained such as bility in aluminum with increasing temperature, clad nonheat-treatable alloys for extra corrosion it is possible to subject them to thermal treatments protection, for brazing purposes, or for special that will impart pronounced strengthening. surface finishes . Some alloys in wire and tubular form are clad for similar reasons, and on an exper - The first step, called heat treatment or solution imental basis extrusions also have been clad. heat treatment , is an elevated-temperature process de signed to put the soluble element or elements Annealing characteristics —All wrought alu - in solid solution . This is followed by rapid minum alloys are available in annealed form. In quenching , usually in water, which momentarily addition, it may be desirable to anneal an alloy “freezes” the structure and for a short time renders from any other initial temper , after working, or the alloy very workable. It is at this stage that between successive stages of working such as in some fabricators retain this more workable struc - deep drawing. ture by storing the alloys at be low freezing tem - peratures until they are ready to form them. At room or elevated temperatures the alloys are not Effect of Alloying Elements stable after quenching , however, and precipitation 1xxx series —Aluminum of 99 percent or higher of the constituents from the super-saturated solu - purity has many applications, especially in the APPENDIX C 10C-2

electrical and chemical fields. These compositions alloying constituents of the latter and so respond are characterized by excellent corrosion to heat treatment to a limited extent. The alloys resistance , high thermal and electrical conductivi - containing appreciable amounts of silicon become ty, low mechanical properties and excellent work - dark grey when anodic oxide finishes are applied, ability . Moderate increases in strength may be and hence are in demand for architectural applica - obtained by strain-hardening . Iron and silicon are tions. the major impurities. 5xxx series —Magnesium is one of the most 2xxx series —Copper is the principal alloying effective and widely used alloying elements for element in this group. These alloys require solu - aluminum. When it is used as the major alloying tion heat-treatment to obtain optimum properties; element or with manganese, the result is a moder - in the heat treated condition mechanical properties ate to high strength non-heat-treatable alloy. are similar to, and sometimes exceed, those of Magnesium is considerably more effective than mild steel. In some instances artificial aging is manganese as a hardener, about 0.8 percent mag - employed to further increase the mechanical prop - nesium being equal to 1.25 percent manganese, erties. This treatment materially increases yield and it can be added in considerably higher quanti - strength , with attendant loss in elongation; its ties. Alloys in this series possess good welding effect on tensile (ultimate) strength is not so great. characteristics and good resistance to corrosion in The alloys in the 2xxx series do not have as good marine atmosphere. However, certain limitations corrosion resistance as most other aluminum should be placed on the amount of cold work and alloys , and under certain conditions they may be on the safe operating temperatures permissible for subject to intergranular corrosion. Therefore, these the higher magnesium content alloys (over about alloys in the form of sheet are usually clad with a 3.5 percent for operating temperatures above high-purity alloy or a magnesium-silicon alloy of about 150°F) to avoid susceptibility to stress the 6xxx series, which provides galvanic protec - corrosion. tion to the core material and thus greatly increases resistance to corrosion. Alloy 2024 is perhaps the 6xxx series —Alloys in this group contain silicon best known and most widely used aircraft alloy. and magnesium in approximate proportions to form magnesium silicide, thus making them heat- 3xxx series —Manganese is the major alloying treatable. The major alloy in this series is 6061, ele ment of alloys in this group, which are gener - one of the most versatile of the heat-treatable ally non-heattreatable. Because only a limited alloys . Though less strong than most of the 2xxx percentage of manganese, up to about 1.5 percent, or 7xxx alloys , the magnesium-silicon (or magne - can be effectively added to aluminum, it is used as sium-silicide) alloys possess good formability and a major element in only a few instances. One of corrosion resistance , with medium strength . these, however, is the popular 3003, which is Alloys in this heat-treatable group may be formed widely used as a general purpose alloy for moder - in the T4 temper (solution heat-treated but not ate- strength applications re quiring good worka - artificially aged) and then reach full T6 properties bility . by artificial aging .

4xxx series —The major alloying element of this 7xxx series —Zinc is the major alloying element group is silicon, which can be added in sufficient in this group, and when coupled with a smaller quantities to cause substantial lowering of the percentage of magnesium results in heat-treatable melting point without producing brittleness in the alloys of very high strength . Usually other ele - resulting alloys . For these reasons aluminum-sili - ments such as copper and chromium are also con alloys are used in welding wire and as brazing added in small quantities. The outstanding mem - alloys where a lower melting point than that of the ber of this group is 7075, which is among the parent metal is required. Most alloys in this series highest strength alloys available and is used in are non-heat-treatable, but when used in welding air-frame structures and for highly stressed parts. heattreatable alloys they will pick up some of the I APPENDIX C 10C-3

2. Typical Properties The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

TABLE 2.1 Typical U.S. Mechanical Properties 1,2

For all numbered footnotes, see page 10C-6. I APPENDIX C 10C-4

TABLE 2.1 Typical U.S. Mechanical Properties 1,2 (continued) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-6. I APPENDIX A 10C-5 I I APPENDIX A 10C-6 APPENDIX C 10C-6

TABLE 2.1 Typical U.S. Mechanical Properties 1,2 (continued) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-6. I I APPENDIX C 10C-7 APPENDIX A 10C-7

TABLE 2.1 Typical Mechanical Properties 1,2 (concluded) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes. I I APPENDIX A 10C-8 APPENDIX C 10C-8

TABLE 2.3 Typical Physical Properties The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-8. I I APPENDIX C 10C-9 APPENDIX A 10C-9

TABLE 2.3 Typical Physical Properties (concluded) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes. I I APPENDIX A 10C-10 APPENDIX C 10C-10

TABLE 2.1m Typical Metric Mechanical Properties 1,2 The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-12. I I APPENDIX C 10C-11 APPENDIX A 10C-11

TABLE 2.1m Typical Metric Mechanical Properties 1,2 (continued) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-12. I I APPENDIX A 10C-12 APPENDIX C 10C-12

TABLE 2.1m Typical Metric Mechanical Properties 1,2 (continued) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-12. I I APPENDIX C 10C-13 APPENDIX A 10C-13

TABLE 2.1m Typical Metric Mechanical Properties 1,2 (continued) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes. I APPENDIX A 10C-14

TABLE 2.3m Typical Metric Physical Properties 1,2 The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes.

For all numbered footnotes, see page 10C-14. I APPENDIX A 10C-15

TABLE 2.3m Typical Metric Physical Properties 1,2 (concluded) The following typical properties are not guaran - any particular product or size. These data are teed, since in most cases they are averages for intended only as a basis for comparing alloys and various sizes, product forms and methods of man - tempers and should not be specified as engineer - ufacture and may not be exactly representative of ing requirements or used for design purposes. I APPENDIX A 10C-16

TABLE 3.3 Comparative Characteristics and Applications

For all numbered footnotes, see page 10C-18. I APPENDIX A 10C-17

TABLE 3.3 Comparative Characteristics and Applications (continued)

For all numbered footnotes, see page 10C-18. I APPENDIX A 10C-18

TABLE 3.3 Comparative Characteristics and Applications (continued)

For all numbered footnotes, see page 10C-18. I APPENDIX A 10C-19

TABLE 3.3 Comparative Characteristics and Applications (concluded) Rolling Aluminum: From the Mine through the Mill 10 APPENDIX D: Aluminum Sheet & Plate Tolerances

o ensure high-quality products with dependable I Length, sheared flat sheet and plate. properties and dimensions, the aluminum indus - I Width, slit coiled sheet. tTry has developed and adheres to standard limits I and tolerances which are routinely applied to alu - Lateral bow, coiled sheet. minum plate, sheet and foil (and other wrought I Lateral bow, flat sheet and plate. products). I Squareness, flat sheet and plate. These standards represent, for each of the I Diameter, sheared or blanked sheet and tolerance d characteristics, the range within which plate circles. the relevant product is to be produced. In most instances, actual deviation from nominal dimen - I Diameter, sawed sheet and plate circles. sions is even smaller than the standard tolerances I Flatness , flat sheet. would allow. I Flatness , sawed or sheared plate. If non-standard tolerances are desired, they I must be negotiated specifically between vendor Thickness, for sheet and plate for aerospace and purchaser. alloys . Adherence to these product standards is volun - tary, but they are broadly accepted by both the alu - Standard tolerances are also provided for minum industry and its customers and often form aluminum duct sheet, commercial roofing and the basis of tolerances incorporated in government, siding, tread plate, and foil . technical society and other specifications. These tolerance tables are presented in: “American National Standard Dimensional Standard Dimensional Tolerances Tolerances for Aluminum Mill Products”, he Aluminum Association developed the indus - ANSI -H35.2 and “American National Standard try's first standard dimensional tolerances , for Dimensional Tolerances for Aluminum Mill Textruded and tubular products, in 1949 and then Products (Metric)”, ANSI -H35.2M, The expanded its efforts, publishing its first standards Aluminum Association. for aluminum mill products in 1955. In 1970, at the request of the Aluminum Association, the American National Standards Standard limits on Non-Dimensional Institute ( ANSI ) authorized establishment of Properties Standards Committee H35 on Aluminum and he Aluminum Association also issues “Standard Aluminum Alloys , which was redesignated in Limits” applied voluntarily to non-dimensional 1983 as the Accredited Standards Committee on pTroperties of aluminum sheet, plate, and other Aluminum and Aluminum Alloys H35. It includes wrought products, in its publications “Aluminum representatives of various branches of the alu - Standards and Data” and “Aluminum Standards minum industry, aluminum-using industries and and Data Metric SI”(Technical Publication #1). the United States Government. ANSI itself does not develop or interpret such These standards include: standards; it accredits standards and revisions I Chemical composition limits of wrought after verifying that they have been developed aluminum alloys . through appropriate consensus procedures. I Ultrasonic discontinuity limits. The standard dimensional tolerances applied to aluminum sheet and plate include: I Lot acceptance criteria for corrosion resistant tempers. I Thickness. I Location for electrical conductivity measure I Width, sheared flat sheet and plate. ments. I Width and length, sawed flat sheet and plate. I APPENDIX D 10D-2

I Fracture toughness limits. Always Refer to I Corrosion resistance test criteria. Most Recent Revisions I Mechanical property limits- non- heat-treatable oth the US customary and metric editions of alloys (sheet and plate). “Aluminum Standards and Data” (ASD) are I Mechanical property limits- heat-treatable pBeriodically updated, revised and republished by alloys (sheet and plate). The Aluminum Association. In addition to The Aluminum Association’s non-dimensional stan - I Mechanical property limits- brazing sheet. dards for wrought aluminum, ASD reprints the I Weights per square foot (by sheet thickness). ANSI standard dimensional tolerances which may, I Weight (/density) conversion factors (by alloy) however, be revised between updates of ASD; in I Recommended minimum bend radii for 90- those circumstances, the latest official ANSI -H35 degree cold forming of sheet and plate. standards take precedence over any earlier ver - sions still in circulation. Therefore, readers who wish to make use of the standards currently in effect are advised to refer to the most recent editions of “American National Standard Dimensional Tolerances for Aluminum Mill Products ( ANSI -H35.2)” (or the metric ver - sion ANSI -H35.2M) for sheet, plate and foil dimensional tolerances ; and “Aluminum Standards and Data” for non-dimensional wrought aluminum standards. These publications are available from The Aluminum Association’s on-linebookstore at www.aluminum.org . Rolling Aluminum: From the Mine through the Mill 10 APPENDIX E: SELF-TEST Questions for Technical Appendices

10.1 “Wrought aluminum alloys and cast 10.4 Alloy 1199 contains a minimum of… aluminum alloys share the same alloy a. 99.00% aluminum. designation numbering system.” This b. 99.90% aluminum. statement is: c. 99.99% aluminum. a. true. b. false. 10.5 Typical yield strength of alloy 2024-O is… a. 11 ksi (76 MPa) 10.2 The aluminum temper designation b. 20 ksi (138 MPa) system uses… c. 26 ksi (179 MPa) a. only letters of the alphabet. b. only numbers. 10.6 Name five Standard Dimensional c. letters followed by numbers. Tolerances applied to aluminum sheet d. numbers followed by letters. and plate.

10.3 The initial symbols of aluminum temper designations are… a. 1, 2, 3, 4, 5 b. A, B, C,D,E c. A,S,D,F,G d. F,O,H,W,T e. the last line of a doctor’s eye chart. Rolling Aluminum: From the Mine through the Mill 10 APPENDIX F: ANSWERS To Self-Test Question SECTION 1: INTRODUCTION 2.11 f. 1.1 Lightweight; strong; cold-resistant; 2.12 c. ductile and workable; joinable; reflec - 2.13 b. tive; heat-conducting; electrically conducting; corrosion resistant; non- 2.14 b. toxic; noncombustible; recyclable. 2.15 c. 1.2 b. 2.16 a. 1.3 c. 2.17 d. 1.4 d. 2.18 a. 1.5 c. 2.19 b. 1.6 b. 2.20 b. 1.7 See Sec.1 2.21 c. 1.8 See Sec.1 2.22 d. 1.9a c. 2.23 a. 1.9b a. 2.24 b. 1.10a b. 2.25 e. 1.10b c. 2.26 b. 1.11 c.Because flat-rolled aluminum 2.27 b. products less than .008-inch thick are defined as foil . 2.28 a. 1.12 d. 2.29 e. 1.13 d. 1,14 c. SECTION 3: PREPARATION 3.1 b. 1.15 b. 3.2 c. 1.16 c. 3.3 b. SECTION 2: PRODUCTION 3.4 b. 2.1 a. 3.5 c. 2.2 c. 3.6 e. 2.3 a. 3.7 b. 2.4 b. 3.8 Titanium, or boron salts. 2.5 c. 3.9 c. 2.6 c. 3.10 c. 2.7 b. 3.11 b. 2.8 b and/or c. 3.12 d. 2.9 d. 3.13 c. 2.10 b. 3.14 d. I APPENDIX F 10F-2

3.15 a. 5.18 b. 3.16 f. 5.19 c. 3.17 c. 5.20 a. 3.18 b. 5.21 Strength , temper , thickness, finish, flatness , and profile. SECTION 4: ROLLING MILL 5.22 c. 4.1 c. 5.23 Roll tilting; roll crossing; localized roll 4.2 a. cooling; roll -bending; stepped backup rolls; axial shifting of sleeved backup 4.3 e. rolls; axial shifting of cylindrical work 4.4 f. rolls ; axial shifting of non-cylindrical work rolls ; flexible backup rolls. 4.5 b. 5.24 a. 4.6 d. 4.7 b. 4.8 c. SECTION 6: SHEET FINISHING 6.1 c. 4.9 b and c. 6.2 b. 4.10 a. 6.3 b. 4.11 a. 6.4 a. 4.12 c. 6.5 b. 4.13 d. 6.6 b. 4.14 c. 6.7 b. 6.8 Mechanical finishes, chemical finishes, SECTION 5: SHEET ROLLING and coatings. 5.1 b. 6.9 c. 5.2 d. 5.3 c. SECTION 7: PLATE ROLLING AND 5.4 c. FINISHING 5.5 b. Because friction in the roll gap 7.1 d. prevents the slab from spreading. 7.2 a. 5.6 d. 7.3 c. 5.7 b. 7.4 b. 5.8 c. 7.5 b. 5.9 d. 7.6 d. 5.10 b and d. 7.7 b. 5.11 a and d. 7.8 a. 5.12 b. 7.9 a. 5.13 Annealed. 5.14 a. SECTION 8: QUALITY AND PROCESS 5.15 c. CONTROL 5.16 c. 8.1 c. 5.17 a. 8.2 b. I APPENDIX F 10F-3

8.3 d. 8.4 d. 8.5 a. 8.6 c.

SECTION 9: GLOSSARY 9.1 b. 9.2 c. 9.3 d. 9.4 b. 9.5 c. 9.6 b. 9.7 d. 9.8 e. 9.9 d.

SECTION 10:TECHNICAL APPENDICES 10.1 b. 10.2 c. 10.3 d. 10.4 c. 10.5 a. 10.6 See Appendix D. Rolling Aluminum: From the Mine through the Mill 11 REFERENCES Altenpohl, D., “Aluminum: Technology, Barten, Axel E. (Achenbach Buschhutten Applications and Environment”, 1998. Gmbh, Achenbach American, Inc., Nashville, TN), “100 Years of Aluminum Rolling Mills”, “Aluminum Statistical Review for 2005”, The Light Metal Age, April 1989. Aluminum Association, Arlington, VA, 2005. Barten, A.E., “Aluminum Strip & Foil Rolling – “Aluminum Standards and Data 2006”, The Leading Technologies on the Market”, Aluminum Association, Arlington, VA, 2006. Aluminum 2002 – Proceedings of the TMS 2002 “Aluminum Standards and Data 2006 Metric Annual Meeting: Automotive Alloys and SI”, The Aluminum Association, Arlington, VA, Aluminum Sheet and Plate Rolling and 2006. Finishing Technology Symposia, TMS, 2002 ® “American National Standard Dimensional Barten, A.E., “Optipure Integrative Tolerances for Aluminum Mill Products”, Technology for Economical and Ecological ANSI -H35.2-2006, The Aluminum Association, Efficiency”, Aluminum 2002 – Proceedings of Arlington, VA. the TMS 2002 Annual Meeting: Automotive Alloys and Aluminum Sheet and Plate Rolling “American National Standard Dimensional and Finishing Technology Symposia, TMS, 2002 Tolerances for Aluminum Mill Products (Metric)”, ANSI -H35.2M-2006, The Aluminum Basson, F., Menet, P-Y., Maiwald, K., and Association, Arlington, VA. Bosch, M., “ Strip Casting Technology – A Key to Product Quality”, Aluminum 2002 – Anderson, M., Bruski, R., Groszkiewicz, D. and Proceedings of the TMS 2002 Annual Meeting: Wagstaff, R.B., “NetCast Shape Casting tech - Automotive Alloys and Aluminum Sheet and nology: A Technological Breakthrough that Plate Rolling and Finishing Technology Enhances the Cost Effectiveness of Aluminum Symposia, TMS, 2002. Forgings,” Light Metals 2001, TMS, pp. 847-853. Black, Philip B., “Laser Flatness Gauging Hot ASM, Metals Handbook, 9th ed., 1981, and Cold Mills”, Proceedings of the Seminar vol. 4, pp. 675... on Rolling Mill Gauge/Shape Profile, June 8- ASM, Metals Handbook, 8th ed., 1964, 9,1988, Atlanta, Ga., The Aluminum vol. 2, pp. 277-278 Association. ASM, Metals Handbook, 9th ed., 1981, Boulot, D., and Christoffel, J.C., “The vol. 4. Shaperoll, An Actuator for Shape and Profile Control in Hot and Cold Aluminum Rolling Atack, P.A., Round, P.F., and Wright, L.C., “An Mills”, Proceedings of the Seminar on Rolling Adaptive Scheduling and Control System for Mill Gauge/Shape Profile, June 8-9,1988, a Single Stand Reversing Mill for Hot Rolling of Atlanta, Ga., The Aluminum Association. Aluminum”, Proceedings of the Seminar on Burnett, C., Carmichael, G., and Jardina, D., Rolling Mill Gauge Shape/Profile, June 8-9, “Truly Universal Non-Contact Thickness 1988, Atlanta, Ga., The Aluminum Association. Sensor”, Aluminum 2002 – Proceedings of the Bachowiski, Ronald; O' Mally, R.J.; and TMS 2002 Annual Meeting: Automotive Alloys Mohajery, M.M., “Continuous Casters for and Aluminum Sheet and Plate Rolling and Aluminum Mini-Sheet Mills-an Alcoa Finishing Technology Symposia, TMS, 2002. Perspective”, Light Metal Age, August 1989. Butler, W.R., “Commercial Forms of Aluminum Alloys ”, in “Aluminum”, Vol. 2, ed. Kent R. Van Barten, Axel E., “Experience With Optiroll Mill Horn, American Society for Metals, 1967. Control Systems”, Proceedings of the Seminar on Rolling Mill Gauge Shape/Profile, June 8- C.M. Taylor, “Impact of AirSlip Technology on 9,1988, Atlanta, GA, The Aluminum Billet Production and Quality of Dubai Association. Aluminum Company Limited,” Proceedings of I REFERENCES 11-2

the Fourth Int’l Aluminum Extrusion Technology Distribution,” Light Metals 2001, pp. 805-811. Seminar, 1988, pp. 79-84. Grealy, G.P., Davis, J.L., Jensen, K., Tøndel, Church, Fred L., “Rolling mill improvements P.A. and Moritz, J., “ Advances for DC Ingot groomed for quality not tons”, Modern Casting: Part 2 – Heat Transfer and Casting Metals, April 1989. Results,” Light Metals 2001, pp. 813-821. Davis, J.L., and Levy, S.A., “Sub-Surface Hegmann, W., “Aluminum Workshop Structure of As-Cast LHC Slabs,” Alumitech Practice”, English ed., edited and revised by 1997, pp. 730-744, The Aluminum Association. A.W. Brace; Techicopy Limited, Gloucester, Davis, J.L., Wagstaff, R.B. and Shaber, C., England, 1978. “Developments in LHC Casting of Wrought “Kaiser Aluminum Sheet and Plate Product Alloys ,” Proceedings of the Fifth Australasian Information”, 2nd ed., 1953; Kaiser Aluminum Pacific Conference on Aluminum Cast House & Chemical Sales, Inc., Chicago, Ill. Technology, Theory and Practice, 1997, pp. Keevil, David J., “Aluminum”, World 253-269. Resources, 1980. Dunn, J. H., and Sewell, L.S., Jr., “Historical Kumar, Surinder, “Overview of a Rolling Mill”, Development of Aluminum Production and in Proceedings, Workshop on Application”, in “Aluminum”, vol. 2, ed. Dent Characterization and Control of Aluminum R. Van Horn, American Society for Metals, Cold Rolling Mill Emissions, Nov. 16-17, 1983, 1967. Clarksville, IN, The Aluminum Association. Emond, C., and Weaver, C., “An Aluminum Nirtanda, Masao: “High Crown Control Mill Plug with Multiple Holes for Self-Draining Sheet with Taper Piston Roll ”, Proceedings of the Ingot Stoolcaps,” Light Metals 1994, pp. 821- Seminar on Rolling Mill Gauge/Shape Profile, 825. June 8-9,1988, Atlanta, GA, The Aluminum Farley, T.W.D., Nardini, D., Rogers, S. and Association. Wright, D.S., “An Approach to Understanding Odok, Adnan M., and Gyongyos, Ivan: Mill Vibrations”, Aluminum 2002 – Proceedings “Alusuisse Caster I and Caster II”, Light Metal of the TMS 2002 Annual Meeting: Automotive Age, Dec. 1975. Alloys and Aluminum Sheet and Plate Rolling and Finishing Technology Symposia, TMS, 2002 Outhwaite, Stephen J.; and Gouel, Roland: “Radiation Thickness Gauging of Aluminum”, Forster, B.J., and Tucker, D., “ Advances in Hot Proceedings of the Seminar on Rolling Mill and Cold Rolling Flatness Control Through Gauge/Shape Profile, June 8-9, 1988, Atlanta, Effective Roll Cooling Processes”, Aluminum GA, The Aluminum Association. 2002 – Proceedings of the TMS 2002 Annual Meeting: Automotive Alloys and Aluminum Petry, C.J., “The Hazelett Twin Belt Caster”, Sheet and Plate Rolling and Finishing Light Metal Age, Dec.1975. Technology Symposia, TMS, 2002 Petry, Charles J. and Szczypiorski, Wojtek: Fusada, Tamotsu, “The Advanced Quality “Update on Continuous Casting of Aluminum Rolls for Aluminum Rolling Mills”, in Alloys by the Twin-Belt Process”, Light Metal Proceedings, Seminar on Rolling Assembly Age, Aug, 1986. Technology, Nov. 4-5, 1987, Chicago, The Platek, Stanley and Desautels, S. Jerry, “The Aluminum Association. Continuous Casting and Direct Rolling of Ginzburg, Vladimir B., Bakhtar, Fereidoon, Wide, Thin Slab into Hot Band by Barmet Tabone, Charles J., “ Strip Profile and Flatness Aluminum Corporation using Secondary Analysis in Application to Rolling of Aluminum Operations and Hazelett Technology”, AIME – and Steel”, Proceedings of the Seminar on February 1990 – Anaheim, CA Rolling Mill Gauge Shape/Profile, June 8-9, Ritzmann, Henry W., “Cleaning of Aluminum 1988, Atlanta, GA, The Aluminum Association. Hot Mill Work Rolls With Cylindrical Brushes”, in Grealy, G.P., Davis, J.L., Jensen, K., Tøndel, Proceedings, Seminar of Rolling Assembly P.A. and Moritz, J., “ Advances for DC Ingot Technology, Nov, 4-5, 1987. Chicago; The Casting: Part 1 - Introduction and Metal Aluminum Association. I REFERENCES 11-3

“Rolling Mills, Rolls, and Roll Making”, Aluminum Extrusion Technology Seminar, 1988, Mackintosh-Hemphill Company, Pittsburgh, pp. 75-78 PA, 1953. Wagstaff, R.B., and Ekenes, J.M., “Innovations Schmiedberg, W.F., “Developments in in Hard Alloy Hot Top Casting Systems,” Equipment to Improve Gauge, Shape and Proceedings of the 5th Int’l Aluminium Profile Control for Aluminum Mills (Hot & Extrusion Technology Seminar, 1992, pp. 39-48. Cold)”, Proceedings of the Seminar on Rolling Wagstaff, R.B., Bowles, K.D., and Allen, Mill Gauge/Shape Profile, June 8-9, 1988, Jeff,“Enhanced Cooling Technique for Rolling Atlanta, GA, The Aluminum Association. and Extrusion Ingot ,” Proceedings of 4th Shaber, C. and Spilker, D., “Wagstaff Epsilon Australasian Asian Pacific Conference on Ingot Casting Technology: Ingot Aluminium Cast House Technology,” TMS, Characteristics and Metallurgical Structure,” 1995, pp. 317-330. Aluminium Cast House Technology – Eighth Wagstaff, R.B. and Bowles, K.D., “Practical Australasian Conference, TMS, 2003, pp. 285- Low Head Casting (LHC) Mold for Aluminium 299. Ingot Casting,” Light Metals 1995, TMS, pp. Shaber, C., “Wagstaff Epsilon Ingot Casting 1071-1075. Technology: Making Casting Easier,” 3rd International Melt Quality Workshop, 2005. Steer, David E. and Adams, Neil, “Torrington Back-up Bearings for Precision Rolling Mills”, in Proceedings, Seminar on Rolling Assembly Technology, Nov. 4-5, 1987, Chicago; The Aluminum Association. Szczypiorski, Wojtek and Szczypiorski, Renata, “The Mechanical and Metallurgical Characteristics of Twin-Belt Cast Aluminum Strip using current Hazelett Technology”, AIME – February, 1991 – New Orleans Szczypiorski, Wojtek, “Importance of Hazelett caster Belt Coatings”, Light Metals 1994, TMS Szczypiorski, Wojtek and Szczypiorski, Renata, “Elimination of Surface Streaking on Finished Sheet Cast on Hazelett Casters”, The Rolling Technology Sessions at Alumitech ’94, The Aluminum Association 1994 Vasily, George, “The Hunter Continuous Casting Process”, Light Metal Age, Oct, 1975. “Visual Quality Characteristics of Aluminum Sheet and Plate” (QCA-1), 2002, The Aluminum Association, Arlington, VA. von Gal, Reed, “Twin-Belt Aluminum Casting- A Technology Which Has Come of Age”, Light Metal Age, April 1989. von Gal, Reed, “The Aluminium Sheet Mill for the New Millennium”, ALUMINIUM, Vol. 76 (2000) 12 Wagstaff, F.E., “An Enhanced Cooling Technique for Air Cushion Hot Top Billet Casting,” Proceedings of the 4th Int’l Rolling Aluminum: From the Mine through the Mill 12 INDEX Actuators 5-9 Coatings (sheet and plate) 6-5 Additives (pre-casting) 3-3 Coiling 4-1, 5-5 Age-softening 5-7 Cold rolling 3-8, 4-6, 5-8, 7-1, 9-2 Aging 2-6, 6-3, 9-1, 9-3, 10B-1, 10b-3, 10B-5, Cold rolling, metallurgy 4-7 10C-1, 10C-2 Cold strength : See “Cryongenic” Alclad 1-5, 8-2, 9-1 Cold-working 9-2 Alloys 1-1, 1-2, 2-1, 2-5, 2-6, 2-7, 2-10, 3-1, 3-3, Computer 3-2, 4-2, 8-3 3-4, 3-7, 3-8, 3-9, 4-4, 4-7, 4-9, 5-6, 5-7, 5-8, 5-9, Computer Integrated Manufacturing ( CIM ) 5-12, 6-1, 6-2, 6-3, 7-1, 7-2, 7-3, 8-2, 9-4, 10A-1, 1-6, 8-3, 8-5 10B-1, 10B-2, 10B-4, 10C-1-19, 10D-1-2, 10E-1, Concaved roll 4-4, 9-2 11-1-2, 12-1-3 Conductivity, electrical 1-1, 10C-7 Alloy designations 2-5, 10A, 10B Conductivity, thermal 1-1, 10C-7 Alloy series 2-5, 2-10, 9-4 Continuous casting 3-3, 9-2 Alloy structure, metallurgy 6-1 Controlled-atmosphere annealing 5-7, 9-2 Alloy analysis 3-1 Coolant /lubricant 4-1-4, 5-2, 5-5, 5-8, 5-9 Alloying 2-5, 2-7 Coolant /lubricant analysis 8-2 Alumina 2-1, 2-2, 2-3, 2-9, 3-2, 9-1-4 Coring (of alloy grains) 3-8 Aluminum oxide 2-1-3, 2-9, 4-3, 9-1-3 Corrosion resistance 1-1, 1-5, 2-5, 5-12, 6-3-4, Aluminum, properties of: 10B-4, 10C-15 See “Properties of aluminum” Cross-rolling 5-3, 5-11, 9-2 Annealing 1-4, 2-6, 2-10, 4-7, 4-9, 5-6, 5-8, 5-11- Crowned roll 4-3--4, 9-2 12, 6-1-7, 9-1-4, 9-7, 10B-1, 10B-4, 10C-1 Cryogenic 1-1 Anode 2-3, 9-1, 9-7 Cryolite 2-2, 2-3, 2-9, 9-2, 9-3 Anodizing 1-2, 8-2, 9-1 Cutting-to-length 6-5 ANSI 8-2, 9-1, 9-4, 10A-1, 10D-1-2, 11-1 DC casting: See “ Direct-chill casting” Applications (of sheet, plate and foil ) 1-1, 1-2 Degreasing (of sheet and plate) 6-5 Artificial aging 2-6, 6-3, 7-3, 9-1 Direct-chill (DC) casting 3-3, 3-4, 3-6-8, 9-2 Back-up rolls 4-1, 4-2, 4-4, 4-6, 5-1, 5-2, 5-9, 9-1 Dislocation, lattice 4-7, 6-1 Bar-coding (of sheet and plate) 6-5 Drive motors 4-1 Batch annealing /treatment 5-7 Drive spindles 4-1, 4-9 Bauxite 2-1, 2-9, 9-1 Drop 3-6, 8-5, 9-2 Bayer Process 2-1, 2-9, 9-1 Ductility 1-1, 4-7, 6-3, 9-2, 9-4-5, 9-7, 10C-3 Belt caster 3-4, 9-1 Edge-trimming 3-7, 5-5, 7-1, 7-3 Bite 4-3, 5-2, 5-3, 9-1, 9-7 Electrical resistivity 10C-7 Block caster 3-5, 9-1 Electromagnetic casting (EMC ) 3-7, 9-2 Brazeability 10C-15 Embossing 5-10, 6-5 Breakdown mill 5-1--3, 7-1, 9-1 EMC: See “Electromagnetic casting” Bright-dipping 8-2, 9-1 Enrichment zone 3-6 Casting 3-3, 9-1 Fatigue strength 10C-3 Centralized controls 8-3 Filtration 3-1--2, 3-9 Chemical (surface) finishes 6-4 Finishes, surface 6-4 Chlorine ( fluxing ) 3-1 Finishing (sheet) 6-1 Cluster mill 4-5-6, 5-11 I INDEX 12-2

Finishing, plate 7-1 Mill stand 4-1, 5-1, 5-9. 9-7 Flatness 4-1, 4-4, 5-9, 6-4, 7-1-2, 8-2 Mining 2-1, 2-2 Flat-rolled products 1-2, 1-4 Modulus of elasticity 10C-3 Flat-rolled shipments 1-2 Multiple-stand mill: See “ Tandem mill ” Flat-rolling 9-2 Natural aging (See also “ Aging ”) 2-6, 6-3, 7-3, Fluxing 3-1 9-3 Flying shears 6-5 Nitrogen ( fluxing ) 3-1 Foil applications 1-2 Nitrogen (gas ) 5-7 Foil definition 1-4, 9-2 Non-combustibility 1-1 Foil 1-2, 1-4, 1-5, 1-7, 2-7, 3-4, 5-8, 8-3, 9-2 Non- heat-treatable alloys 2-6, 9-3, 10C-1 Four-high mill 1-6, 4-2, 4-4, 4-5, 5-1, 9-2 Non-toxicity 1-1 Full annealing 5-6, 9-2 Nucleation 3-3, 9-3 Gauge control 1-6, 5-8 Oiling (of sheet and plate) 6-5 Gearboxes 4-1, 4-2 One-side-bright mill finish 8-2 Glide planes 4-7 Ore (of aluminum): See “ Bauxite ” Grain 3-8-9, 4-7, 5-7, 8-1, 9-2 Over- aging 6-3 Grain refiner (additive) 3-3 Packaging 1-1, 1-2, 6-6 Hall-Heroult Process 1-4, 1-8, 2-2, 2-4, 2-9, 9-2 Partial annealing 5-6, 5-7, 9-3 Hardness 2-6, 4-3, 5-7, 6-3, 7-5, 8-5, 9-4, 10C-3 Pinning (of lattice dislocations ) 6-2, 6-3 Heat-treatable alloys 2-5-6, 5-6, 6-1, 9-3, 10C-1 Plate finishing 7-1 Heat-treatment 2-6, 6-1, 6-3, 9-3 Plate rolling 7-1 High-voltage spark spectrometer 3-2 Plate definition 1-4, 9-3 Homogenization 3-3, 3-8, 9-3 Plate 1-2, 1-4 Hot rolling metallurgy 4-7 Plate applications 1-2 Hot rolling 3-3-4, 3-8, 3-10, 4-7, 4-9, 5-3, 9-3 Porosity testing 8-1 Hot working 3-3, 9-3-4 Pot (Hall-Heroult process ) 2-2, 2-3, 9-3 Hydrogen (gas) 2-5, 2-9, 2-11, 3-1-2, 3-9 Potline 2-2, 2-3, 9-3 Inclusions 3-2, 3-9, 7-5, 8-1 Precipitates 3-8, 6-2-3, 9-1 Ingot 2-7, 3-2-4, 3-6-8, 5-1, 5-3, 8-5, 9-3 Precipitation hardening : See “ Aging ” 9-3 Ingot casting 3-3, 3-4 Precipitation heat treatment: Intermediate edge trimming 7-1 See “Artificial aging ” Intermediate hot-rolling 5-3 Pre-heating (of ingot ) 3-5, 9-3 Joinability 1-1 Process control 1-6, 5-7. 8-1, 8-3, 8-5 Just-In-Time (JIT ) 1-6, 8-3 Profiles 5-9 Lattice , crystal 4-7, 6-1 Properties, typical, of aluminum alloys 10C-1 Leveling 1-4, 6-4, 6-6, 9-3 Physical 2-5, 4-1, 4-4, 7-2, 8-3, 9-4, 10C-7 Lubricant: See “ Coolant /lubricant” Property tables 10C, 10C-3 Machinability 10C-15 Pure aluminum 2-5, 2-7, 2-9, 5-8, 9-3, 10C-1 Mechanical 10C-3 Quality control 1-6, 8-1 Mechanical (surface ) finishes 6-4 Quenching (plate) 7-2 Melting point (and solution heat treatment ) Quenching 6-1, 6-2, 7-2, 9-3 6-2 Recrystallization 5-6, 9-3 Melting ranges 10C-7 Recrystallization temperature 3-8, 5-6, 5-12, 9-3 Microscopic inspection 8-1 Recyclability 1-1 Mill, rolling 9-3 Recycling 2-5, 2-7 Mill finish 4-3, 4-9, 8-2, 9-3 Reduction (of alumina): I INDEX 12-3

See “Hall-Heroult Process” Stand, rolling 9-4 Refined aluminum 9-3 Standard bright finish 8-2 Reflectivity 1-1 Standard Tolerances : See “ Tolerances ” 9-4 Reheating 3-4, 7-1, 9-3 Statistical Process Control (SPC) 1-6, 8-3, 8-5 Reversing mill 4-4, 5-1, 5-4, 9-4, 11-1 Stenciling (of sheet and plate) 6-5 Roll 1-5, 1-6, 4-3, 5-9, 9-4 Storage 6-5-6, 7-3, 8-2 Roll caster 3-4, 3-9, 9-4 Strain-hardening 2-6, 3-8, 4-6-7, 4-9, 5-7, 9-4 Roll gap 3-4, 4-1-3, 4-9, 5-1, 5-3, 5-5, 5-9-11, 9-3 Strength 1-1, 4-7 Roll coating 4-3 Stress-relief 5-7, 7-2, 9-4 Roll configurations 4-4 Stress-relief (stretching) 7-2 Roll benders 4-1, 5-9 Stretcher- leveling 6-6, 9-4 Rolled-to- temper 5-7 Stretching (plate ) 7-2 Rolling (general description) 1-4, 9-3 Strip 1-6, 3-3-4, 5-4, 5-8, 5-9, 6-3, 6-4, 9-4 Rolling aluminum, history 1-4 Strip casters 3-4 Rolling aluminum, technological advances 1- Surface quality 4-3, 8-2 5 Surface finishes 5-8, 6-4, 10C-1 Rolling mill, general 4-1, 5-1 Table rolls 5-3, 5-11, 9-5 Scalping 1-4, 3-3, 3-6-7, 3-10, 9-4 Tandem mill 4-3, 5-4, 5-5, 5-8-11, 9-5, 9-7 Segregation 3-3, 3-8 Temper 2-6, 4-7, 5-2, 5-6-8, 5-12, 6-3, 6-5, Series (alloy) 2-5, 10C-1 9-2, 9-5, 10A-1, 10B-1 Shear strength 10C-3 Temper designations 10B-4, 10C-1, 10E-1 Strength 1-1, 4-7 Tensile strength testing 8-1 Sheet applications 1-2 Tensile strength 2-6, 8-1, 9-7, 10B-1-3, 10C-3 Sheet rolling 1-6, 4-4, 5-1-11, 10F-2 Thermal expansion coefficients 10C-7 Sheet definition 1-4, 9-4 Tension-leveler 6-4, 9-5 Sheet hot rolling 5-4 Testing/ Inspection 7-2-3, 8-1 Sheet annealing /treatment 5-7 Texturing 5-10 Sheet 1-2, 1-4 Thermal treatment 9-1, 9-3, 9-4, 9-5, 10B-1 Shrinkage gap 3-6-7 Titanium ( titanium diboride ) additive 3-3 Single-stand mill 4-3, 5-1, 5-8, 9-4 Tolerances 4-1, 8-2, 8-5, 9-1, 9-4, 9-5, 10B-5, Skin-quality finish 8-2 10D-1-2, 11-1 Slab 9-4 Two-high mill 1-6, 4-4, 4-5, 9-5 Slab reheating 7-1 Typical Properties, tables (aluminum alloys ) Slab casting 3-4 10C Slitting 1-4, 6-4 Ultrasonic inspection 7-2, 8-1, 9-5 Soak (definition) 9-4 Weight 1-1, 1-7, 2-1, 2-9, 3-3, 10D-2 Soaking ( solution heat treatment ) 6-2 Weldability 10C-15 Soaking (heat) 3-5 Workability 1-1, 10C-2, 10C-15 Soaking pit 3-8 Walking -beam furnace 3-8 Solid solubility 2-6, 6-2, 6-7,10C-1 Work (definition) 9-5 Solid solution 3-8, 5-7, 6-3, 9-1, 9-3, 9-4 Work hardening 4-7, 5-6, 5-8, 5-11, 9-2 Solution heat treatment 1-4, 5-6, 6-2, 6-7, 7-2, Work rolls 1-6, 3-9, 4-1-4, 4-6, 4-9, 5-1-3, 5-8-11, 9-4 6-4, 8-2, 9-5, 9-7, 10F-2, 11-2 Special tolerance 9-4 Wrought product (definition) 9-5 Spheroidizing 3-8 Stabilization (anneal ) 5-7, 9-4 I INDEX 12-4