DOCSLIB.ORG

FUNDAMENTALS of METAL CASTING 0. Alloys and Phase

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
FUNDAMENTALS of METAL CASTING 0. Alloys and Phase 0. Alloys and Phase Diagram FUNDAMENTALS OF • Pure Metals • Alloys Substitutional – Solid solutions Solid Solution METAL CASTING • Substitutional Solid Solution (Zn/Cn and Cu/Ni) – Atomic radii is similar – Lattice type is the same 0. Phase Diagram • Interstitial Solid Solution – Smaller atoms are interstitially located among 1. Overview bigger atoms 2. Heating & Pouring – Lattice type usually does not change 3. Solidification and Cooling – Intermediate Phases – The solubility of one Interstitial element in another element is limited. Solid Solution • Metallic compounds (Fe3C) • Intermetallic compounds(Mg2Pb) 1 2 Cu-Ni Phase Diagram Pb-Sn Phase Diagram (°C) T T 1600 T 600 Liquid Eutectic Composition Temperature, °F Temperature, and Temperature 1400 500 L L+S α+L 400 α β+L 1260 362 °F β 61.9% Sn 1200 300 Solid 200 α+β Substitutional Solid Alloys α 1000 100 Time Time Time Cu26% 36% 50% 62% Ni Pure Metals Pure Metals 0 Time L S Pb (lead) Sn (Tin) 3 4 Fe-C Phase Diagram Introduction • Dated back 6000 years 1800 δ • Ingot vs. Shape casting L • Polymers and ceramics are cast as well. 1400 L+θ • Issues in casting γ+L γ 1130 – Flow 1000 γ+θ – Heat Transfer – Selection of Mold Materials α 723 – Solidification- Nucleation and Growth 600 • Depending on how we control solidification, these α+θ events influence the size, shape, uniformity and 200 chemical composition of the grains. Fe1 23456 C 5 6 1 Introduction Classification • Casting (process) – melt the metal, pour into a Sand Casting mold by gravity or other force and solidify. Shell Molding Vacuum Molding • Casting (Part) Metal casting Expandable-mold Casting Expanded Polystyrene • Advantages Investment Casting – Complex geometries – external and internal Plaster-Mold Casting – Can be net-shaped or near net-shaped Solidification – Can produce very large parts Process Ceramic-Mold Casting permanent-mold Permanent-Mold Casting – Any metals Glassworking Casting – Can be mass-produced Variations of Permanent-Mold Casting – Size variety – big and small Die Casting • Disadvantages Extrusion – Limitation in mechanical properties, porosity, Polymers & PMC Centrifugal Casting – Dimensional accuracy, surface finish Processing Injection Molding – Safety Hazard Other Molding – Environmental problems Special Molding for PMC 7 8 1. Overview Two Main Categories • A Foundry is a casting factory which equipped for making molds, melting and handling molten metal, 1. Expendable mold processes –A mold after process performing the casting process, and cleaning the must be destroyed in order to remove casting finished casting – Mold materials: sand, plaster and similar materials + binders – Foundrymen are workers. – More intricate geometries • Open Molds – Simple parts 2. Permanent mold processes –A mold can be used • Closed Molds – Complex parts. many times to produce many castings – A passageway - the gating system leading into the cavity – Mold: made of metal and, less commonly, a ceramic • Two categories -Expandable or permanent molds. refractory material – Part shapes are limited – Permanent mold processes are more economic in high production operations 9 10 (a) open mold (b) closed mold Basic features of Molds Casting Processes • Forming the Mold Cavity Downsprue • Sand Casting Molds Parting – Mold cavity is formed by packing sand around a pattern. line – The pattern usually oversized for shrinkage is removed. – Mold: cope (upper half) & Pouring Riser cup – Sand for the mold is moist and contains a binder to maintain shape drag (bottom half) • Cores in the Mold Cavity – Flask - containment – The mold cavity - the external surfaces of the cast part – Parting line Cope Mold –A core, placed inside the mold cavity to define the interior geometry of part. In sand casting, cores are made of sand. – Pattern – the mold cavity • Gating System - Channel through which molten metal – The gating system – pouring Drag flows into cavity cup, (down)sprue, runner Flask – A downsprue, through which metal enters a runner – Riser – a source of liquid – At top of downsprue, a pouring cup to minimize splash and Core turbulence metal to compensate for Runner shrinkage during solidification • Riser - Liquid metal reservoir to compensate for shrinkage during solidification – The riser must be designed to freeze after the main casting 11 solidify. 12 2 Pouring Analysis 2. Heating & Pouring • Bernoulli’s theorem at any two points in a flowing 2 2 • Sufficient to melt and raise the molten metal to a right liquid P1 v1 P2 v2 state h1 + + = h2 + + ρ 2g ρ 2g • Total Heat Energy required: • h=head, P=pressure, ρ=density, v=flow velocity, g=gravity, F=friction loss H=ρV[C (T -T )+H +C (T -T )] s m o f l p m – Assuming no frictional loss and same pressure where ρ=density, V=volume, Cs=specific heat for solid C =specific heat for liquid, T =melting temperature 2 2 l m v1 v2 T =starting temperature, T =pouring temperature h1 + = h2 + o p 2g 2g • Factors affecting ‘pouring’ 1 – Pouring temperature (vs. melting temp.) – Assuming point 2 is reference (h2=0) and v1=0, – Pouring rate 2 v2 • Too slow, metal freezes h1 = ; v2 = 2gh1 • Too high, turbulence 2g – Turbulence • Continuity law Q = v A = v A 2 • Accelerate the formation of oxides 1 1 2 2 V • Mold erosion • Mold fill time (MFT) MFT = •Voids? 13 Q 14 Fluidity 3. Solidification(Pure Metals) • Fluidity: A measure of the capability of a metal to flow into and fill the mold before freezing. (Inverse of viscosity) Transformation of molten metal Pure Metals • Factors affecting fluidity - Pouring temperature, Metal composition, Viscosity, Heat transfer to the surroundings, Heat of fusion and Solidification into solid state • Higher Re, greater tendency for turbulence flow • Solidification differs Pouring – Turbulence and laminar flow depending on a pure temperature Reynold’s number: Re=vDr/h Temperature element or an alloy Liquid cooling Re ranges 2,000(laminar) to 20,000 (mixture of laminar-turbulence) • For Pure Metal Freezing greater than 20,000 turbulence resulting in air entrainment and dross Tm (scum) formation – Super(Under)cooling temperature Local • Minimize turbulence by avoiding a certain range in flow direction – Solidification occurs at a solidification constant temperature and time Solid cooling Pure metals: good fluidity supercooled Temperature Total solidification time Alloys: not as good – Actual freezing during the local solidification time Time Tests for fluidity [Schey, 2000] 15 16 Solidification of Pure Metals Dendrite Growth • A thin skin of solid metal is formed at the cold mold wall immediately after pouring • Skin thickness increases to form a shell around the molten metal as solidification progresses S • Rate of freezing depends on L heat transfer into mold, as well as thermal properties of the metal Randomly oriented grains of small size Temp. Temp. Temp. near the mold wall, and large columnar grains oriented toward the center of the Slower casting (Dendritic growth) Heat Transfer 17 18 3 Solidification of Alloy Solidification of Alloys • Most Alloys freeze over a temperature range, not at a single temperature. 4 3 2 ∆Gt = πr ∆Gv + 4πr γ • Nucleation 3 ∆Gt – Energy involved in homogeneous nucleation Pouring L Temperature temperature – Total free energy change: Liquid cooling where ∆ G v =volume free energy r L+S = radius of embryo Freezing γ temperature = specific surface free energy r r* Solid cooling • Chemical compositional gradiency within a single grain S Total solidification time • Chemical compositional gradiency throughout the casting – ingot segregation Time Ni Cu • Eutectic Alloys – Solidification occurs at a single temperature Dendritic Growth cooling curve for a 50%Ni-50%Cu composition during casting 19 20 pattern shrinkage allowance Solidification Time Shrinkage Simplification • Chvorinov’s Empirical relationship: Solidification time as a function of the size and shape Metal Volume Contraction Solidification Thermal n ⎛V ⎞ Contraction Aluminum TST = Cm ⎜ ⎟ 7% 5.6% ⎝ A ⎠ Al alloys 7 5 V=volume A=surface area and n=2 Gray cast iron 1.8 3 Gray Cast Iron 0 3 Cm=experimentally determined value that depends on with High C mold material, thermal properties of casting metal, Low C Cast Steel 3 7.2 and pouring temperature relative to melting point Copper 4.5 7.5 • A casting with a higher volume-to-surface area ratio Bronze 5.5 6 solidifies more slowly than one with a lower ratio • Used in riser design: the solidification time of the riser • Exception: cast iron with high C content because of graphitization must be equal to the solidification time of the cast part. during final stages causes expansion that counteracts volumetric 21 decrease associated with phase change 22 Directional Solidification • To minimize the damage during casting, the region most distant from the liquid metal supply needs to METAL CASTING freeze first and the solidification needs to procede PROCESSES toward the riser. • Based on Chvorinov’s rule, the section with lower V/A ratio should freeze first. 1. Sand Casting 2. Other Expandable Mold Casting Processes • Use ‘Chills’: Internal and External chills which 3. Permanent Mold Casting Processes encourage rapid cooling. 4. Foundry practice 5. Casting Quality External Chills 6. Metals for Casting Internal Chills Made of metal 7. Product Design Consideration 23 24 4 Introduction 1. Sand Casting • Casting of Ingot and Shape casting • Most widely used casting process. • Major Classification • Parts ranging in size from small to very large • Production quantities from one to millions – Expandable Mold • Sand mold is used. • A new mold
Load more

Recommended publications
  • Low-Pressure Casting of Aluminium Alsi7mg03 (A356) in Sand and Permanent Molds
    MATEC Web of Conferences 326, 06001 (2020) https://doi.org/10.1051/matecconf/202032606001 ICAA17 Low-Pressure Casting of Aluminium AlSi7Mg03 (A356) in Sand and Permanent Molds Franco Chiesa1*, Bernard Duchesne2, and Gheorghe Marin1 1Centre de Métallurgie du Québec, 3095 Westinghouse, Trois-Rivières, Qc, Canada G9A 5E1 2Collège de Trois-Rivières, 3500 de Courval, Trois-Rivières, Qc, Canada, G9A 5E6 Abstract. Aluminium A356 (AlSi7Mg03) is the most common foundry alloy poured in sand and permanent molds or lost-wax shells. Because of its magnesium content, this alloy responds to a precipitation hardening treatment. The strength and ductility combination of the alloy can be varied at will by changing the temper treatment that follows the solutionizing and quenching of the part. By feeding the mold from the bottom, the low-pressure process provides a tranquil filling of the cavity. A perfect control of the liquid metal stream is provided by programming the pressure rise applied on the melt surface. It compares favorably to the more common gravity casting where a turbulent filling is governed by the geometry of the gating system. 1 The low-pressure permanent 2) The very efficient feeding achieved via the mold process bottom feeder tube by applying a pressure of up to one atmosphere to the melt; the resulting yield is very high, typically 80-90% versus 50-60% for The low-pressure permanent mold casting gravity casting. However, the low-pressure (LPPM) [1], schematized in Figure 1a and shown process cannot pour any casting geometries. in Figure 1b and 1c, is a common process Low-pressure sand casting (LPS) is much less producing high quality castings resulting from common than LPPM; the sand mold rests on top two main characteristics: of the pressurized enclosure as shown in Figure 1) The perfectly controlled quiescent filling 1d.
    [Show full text]
  • OVERVIEW of FOUNDRY PROCESSES Contents 1
    Cleaner Production Manual for the Queensland Foundry Industry November 1999 PART 5: OVERVIEW OF FOUNDRY PROCESSES Contents 1. Overview of Casting Processes...................................................................... 3 2. Casting Processes.......................................................................................... 6 2.1 Sand Casting ............................................................................................ 6 2.1.1 Pattern Making ................................................................................... 7 2.1.2 Mould Making ..................................................................................... 7 2.1.3 Melting and Pouring ........................................................................... 8 2.1.4 Cooling and Shakeout ........................................................................ 9 2.1.5 Sand Reclamation .............................................................................. 9 2.1.6 Fettling, Cleaning and Finishing....................................................... 10 2.1.7 Advantages of Sand Casting............................................................ 10 2.1.8 Limitations ........................................................................................ 10 2.1.9 By-products Generated .................................................................... 10 2.2 Shell Moulding ........................................................................................ 13 2.2.1 Advantages......................................................................................
    [Show full text]
  • Cupola Practice in Modern Gray Iron Foundry
    Scholars' Mine Professional Degree Theses Student Theses and Dissertations 1924 Cupola practice in modern gray iron foundry George E. Mellow Follow this and additional works at: https://scholarsmine.mst.edu/professional_theses Part of the Mechanical Engineering Commons Department: Recommended Citation Mellow, George E., "Cupola practice in modern gray iron foundry" (1924). Professional Degree Theses. 56. https://scholarsmine.mst.edu/professional_theses/56 This Thesis - Open Access is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Professional Degree Theses by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. CUPOLA PHAC11ICE IN MODERN GRAY IRON FlOUNDRY BY GEORGE E. MELLOW A "THESIS submitted to the faculty of the SCHOOL OF MINES AND ~~TALLURGY OF THE UNIVERSITY OF MISSOURI in partial fulfillment of the work required for the Degree Of' Mechanica.l Engineer St. Louis, Mo. 1924 Approved by.?f'..Q... .. Cupola Practice in Modern Gray-Iron Ii'oundry Cupola practice, as described in this paper, 'will include only the practical operation or a cupola and the details of the work necessary in daily routine, and very little of the theory of combustion,or history of cupola development, is presented. A brief ~escription of the cupola will give an idea of its construction, and the names of the parts may be found on the sketch herewith. The cupola consists of a steel shell, cylindrical in shape, which stands veDtically on four cast-iron legs, about four feet off the floor; it is open at the top, and has SWinging cast-iron doors at the bottom.
    [Show full text]
  • Implementation of Metal Casting Best Practices
    Implementation of Metal Casting Best Practices January 2007 Prepared for ITP Metal Casting Authors: Robert Eppich, Eppich Technologies Robert D. Naranjo, BCS, Incorporated Acknowledgement This project was a collaborative effort by Robert Eppich (Eppich Technologies) and Robert Naranjo (BCS, Incorporated). Mr. Eppich coordinated this project and was the technical lead for this effort. He guided the data collection and analysis. Mr. Naranjo assisted in the data collection and analysis of the results and led the development of the final report. The final report was prepared by Robert Naranjo, Lee Schultz, Rajita Majumdar, Bill Choate, Ellen Glover, and Krista Jones of BCS, Incorporated. The cover was designed by Borys Mararytsya of BCS, Incorporated. We also gratefully acknowledge the support of the U.S. Department of Energy, the Advanced Technology Institute, and the Cast Metals Coalition in conducting this project. Disclaimer This report was prepared as an account of work sponsored by an Agency of the United States Government. Neither the United States Government nor any Agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any Agency thereof. The views and opinions expressed by the authors herein do not necessarily state or reflect those of the United States Government or any Agency thereof.
    [Show full text]
  • S Foundry Solutions By: Ricardo Volkmann Index
    Issue #2 Adolf′s Foundry Solutions by: Ricardo Volkmann www.foundrysupply.com Index: Mission Statement & History 3 Style ~A~ Alignment Inserts 4 Alignment Core Prints 4 Wood Cutting Tools 4 Style ~B~ Alignment Inserts 5 Alignment Core Boxes 5 Single Cavity Filtering Basins 6-7 Double Cavity Filtering Basins 6 Pouring Basins 6 Riser Rings 7 Filtering Runner Basins 7 14 Inch Sprues 8 Filtering Sprue Plugs 8 Pop-up Sprue Basins 9 Single Faced Basins 10-11 Pyramid Style Basins 10-11 Three Faced Basins 10 Sprue Pins 10-11 Filtering Basin 10 Four Faced Basins 11 Test Bar Basins 12-13 Inter-Changeable Test Bars 12-13 Test Wedges Basins 12-13 Inter-Changeable Test Wedges 12-13 Test Coupon Basins 12 PIG Boxes 13 Photo Gallery 14-15 Silent Adjustable Vibrator 16 DuraTech Tooling Material 16 Buy direct and save... No sales tax in Oregon 2 www.foundrysupply.com Mission Statement “Doing it Right the First Time” Our mission is to provide new lean manufacturing practices to the foundry industry. Adolf’s Foundry Solutions are products made with the highest integrity, they are dependable, exteremly durable and very cost effective. History 1949 Adolf started his pattern maker apprenticeship in Berlin, Germany during 1949. Trained by German master craftsmen, Adolf excelled as an apprentice and completed a four year apprenticeship program in three years, allowing him to graduate at the top of his class with honors. In Germany, at that time, it was mandatory practice for all apprentices to spend six weeks working in a foundry doing piece work on the molding line.
    [Show full text]
  • Molding & Machining: Metalwork in Geneva
    MOLDING & MACHINING: METALWORK IN GENEVA This is a story of change. In the mid-1800s, Geneva claimed the most foundries in western New York State. The metal industry accounted for almost 70% of the city’s jobs in the 1950s and remained strong until the 1970s. Today, Geneva has only one major metal fabrication company. Geneva was not near iron ore or coal but 19th-century canals and railroads allowed access to raw materials. Demand for new products, from farm equipment to heating systems, allowed foundries to flourish. New factories changed Geneva’s landscape and affected its environment. Ultimately, 20th-century changes in technology and economics – and failure to adapt to change – caused most of the city’s metal industry to disappear. A foundry melts refined iron and pours it into molds to create cast iron. It is brittle but, unlike wrought iron pounded out by a blacksmith, objects can be mass produced in intricate shapes. Molding room at Phillips & Clark Stove Company Machining is the shaping of metal, and other materials, through turning, drilling, and milling. Machining tools were powered by steam engines in the 19th century and later by electricity. Machinists bent sheet metal to make cans, stamped metal for tableware, and milled stock to create machine components. Tool Room at Herendeen Manufacturing Company, 1907 This is a companion exhibit to Geneva’s Changing Landscapes in the next gallery, which has more information and artifacts about local industry. Support for this exhibit is provided by Rosalind Nester Heid in memory of her grandfather Samuel K. Nester, Sr. The First Geneva Foundries Refineries require iron, sand, water, fuel, and people.
    [Show full text]
  • Metals in the Bible: Silver (Part 1)
    The Testimony, August 2004 329 times of restitution of all things” (Acts 3:21, AV). the last verse of his song does look forward to In contrast, the song of Moses in chapter 32 pre- the time of blessing when the Gentiles will re- dicts future rebellion and consequent punish- joice with God’s people and atonement will have ment that would occur before the final glory been provided for both land and people (v. 43). would be attained by the nation. Nevertheless, (To be continued) New feature Metals in the Bible 3. Silver (Part 1) Peter Hemingray In 1996 and 1997 The Testimony published two two-part articles under the title, “Metals in the Bible”, in which we looked at iron and copper.1 We considered the ancient technology of iron, and how this knowledge helps illuminate the Biblical references to it. In particular, we saw how the introduction of iron during the period of the conquest affected the Israelites, who had to overcome superior technology through the power of God. For copper (or brass, as the AV terms it) the ancient metalworking methods were illuminated with illustrations from Timnah in Palestine, and we argued for the symbology of copper in the Bible being primarily that of strength, and only rarely that of the strength of sin. The intention was to complete these studies on metals of the Bible by considering silver, then gold. This we have now done in two further two-part articles to be published in this and the coming months, God willing. E WILL CONTINUE the theme of il- • examine the references to refining and cruci- lustrating the Biblical passages about bles in the light of our knowledge of ancient Wmetals with descriptions of the ancient metalworking practices metalworking techniques, as we consider silver, • look at the few references to lead in the Bible, the next metal up in Nebuchadnezzar’s image often associated with silver for reasons we after the iron and brass already considered.
    [Show full text]
  • Chapter 11: Metal Casting Processes and Equipment
    Manufacturing Engineering Technology in SI Units, 6th Edition Chapter 11: Metal Casting Processes and Equipment Copyright © 2010 Pearson Education South Asia Pte Ltd Chapter Outline ¨ Introduction ¨ Expendable-mold, Permanent-pattern Casting Processes ¨ Expendable-mold, Expendable-pattern Casting Processes ¨ Permanent-mold Casting Processes ¨ Casting Techniques for Single-crystal Components ¨ Rapid Solidification ¨ Inspection of Castings ¨ Melting Practice and Furnaces ¨ Foundries and Foundry Automation Copyright © 2010 Pearson Education South Asia Pte Ltd Introduction ¨ Various casting processes developed over time to meet specific design requirements Copyright © 2010 Pearson Education South Asia Pte Ltd Introduction ¨ Molding categories: 1. Expendable molds 2. Permanent molds 3. Composite molds Copyright © 2010 Pearson Education South Asia Pte Ltd Introduction ¨ General characteristics of sand casting and casting processes are summarized Copyright © 2010 Pearson Education South Asia Pte Ltd Expendable-mold, Permanent-pattern Casting Processes: Sand Casting ¨ Most prevalent form of casting ¨ Application for machine bases, large turbine impellers, propellers, plumbing fixtures Copyright © 2010 Pearson Education South Asia Pte Ltd Expendable-mold, Permanent-pattern Casting Processes: Sand Casting Sand ¨ Sand-casting operations use silica sand as the mold material ¨ Sand is inexpensive and suitable high melting point process ¨ 2 types of sand: naturally bonded (bank sand) and synthetic (lake sand) ¨ Fine grained sand enhances mold strength and lower mold permeability Copyright © 2010 Pearson Education South Asia Pte Ltd Expendable-mold, Permanent-pattern Casting Processes: Sand Casting Types of Sand Molds 3 basic types: 1. Green-sand mold Sand in the mold is moist or damp while the metal is being poured into it 2. Cold-box mold Organic and inorganic binders are blended into the sand to bond the grains chemically 3.
    [Show full text]
  • The One-Shot Casting Process What Is One-Shot Casting?
    The One-Shot Casting Process What is One-Shot Casting? Plaster mold casting is a method of producing aluminum, zinc or magnesium castings by pouring liquid metal into plaster (gypsum) molds. At Armstrong Mold, there are two methods of plaster mold casting: 1) Rubber Plaster Molding (RPM): Patterns create foundry tooling that makes copes, drags and core boxes used to create the plaster molds. 2) One-Shot Casting: Plaster is poured directly on patterns, which are melted out in a furnace cycle. Following is the process for the One-Shot method of making plaster mold castings. Step 1: Model/Pattern 1) Constructed from customer drawing or CAD file. 2) Laser-sintered patterns are produced. 3) Model is engineered to include: A) Metal shrinkage. B) Mold taper (if required) C) Machine stock (if required). 4) We can "clone" or adapt customer-supplied model if requested. Step 2: Plaster Mold 1) A liquid plaster slurry is poured around the pattern. 2) The plaster mold is heated in a furnace to melt out the pattern and cure plaster. Step 3: Pour Casting 1) Molten metal is prepared by degassing, and a spectrographic sample is taken to check the chemical analysis. 2) The molten metal is then poured into the plaster mold. 3) The plaster is removed by mechanical knock-out and high pressure waterjet. 4) When the casting has cooled, the gates and risers are then removed. Step 4: Secondary Operations 1) The raw castings are inspected and serialized. 2) Castings may then require (per customer specifications): A) Heat treatment B) X-Ray C) Penetrant inspection 3) After finish inspection, casting is ready for: A) Machining B) Chemical film, chromate conversion, paint special finishes D) Assembly E) Form-in-place gasketing.
    [Show full text]
  • DROSS in DUCTILE IRON by Hans Roedter, Sorelmetal Technical Services
    98 DROSS IN DUCTILE IRON by Hans Roedter, Sorelmetal Technical Services WHAT IS “DROSS ”? magnesium with other elements. Dross also Dross is a reaction product which is formed from occurs in the form of long stringers instead of Mg treatment and during subsequent reoxidation concentrated “slag like” areas. When it occurs in of Mg rejected from the molten metal before it this string like form it acts like cracks or flake solidifies. It is therefore just another word for a graphite in the structure and so fatigue strength specific type of slag (reaction product). and impact strength of the material are lowered considerably. The reaction binds magnesium with sulphur, oxygen and silicon and forms continuously. This “dross” is light weight and so it will generally be found in the upper surfaces and under cores, but it can be entrained throughout the metal as well, especially with colder pouring tempera - tures. It is very difficult to completely avoid the reaction of magnesium with these other elements, since we need magnesium to form nodules. We are always confronted with the problem of dross in the production of Ductile Iron. WHAT IS PROMOTING “DROSS ” AND WHAT CAN BE DONE TO KEEP THE “DROSS ” OUT OF THE CASTING ? Since “dross” is always connected with magnesium, it is necessary to keep the magnesium level as low as possible. Good inoculation practice with some late inoculation in conjunction with sufficient magnesium will When looking at “dross” in the microscope you produce nice round small nodules. See will almost always find flake graphite in Suggestion Sheet 76.
    [Show full text]
  • Lecture 8: Casting Technology
    Lecture 8: Casting Technology MT321: Principles of Materials Processing Lecture 8:Casting Technology 1 Design of Gating Systems Functions of a gating system: To deliver liquid metal to mould cavity within a short time. To minimise turbulent flow. To keep dross and/or inclusion particles from entering mould cavity. MT321: Principles of Materials Processing Lecture 8:Casting Technology 2 MT321: Principles of Materials Processing Lecture 8:Casting Technology 3 How to deliver liquid metal fast? By using a sufficient large cross sectional area; By using multiple runners. How to minimise turbulent flow? By using tapered sprue and runners. By bottom filling of the liquid into the mould cavity. By regulating the change of cross sectional area of the channels according to fluid dynamics principles. MT321: Principles of Materials Processing Lecture 8:Casting Technology 4 How to keep dross and inclusion particles from entering mould cavity? By using dross traps. By using filters. MT321: Principles of Materials Processing Lecture 8:Casting Technology 5 Various types of ceramic filters that may be inserted into the gating systems of metal castings MT321: Principles of Materials Processing Lecture 8:Casting Technology 6 MT321: Principles of Materials Processing Lecture 8:Casting Technology 7 Solidification Shrinkage The liquid of most metals and alloys shrinks during solidification. Solidification shrinkage (percent) of some common engineering metals and alloys MT321: Principles of Materials Processing Lecture 8:Casting Technology 8 Two considerations must be made in designing a casting mould, due to the solidification shrinkage: A riser, which is a reservoir of liquid, is needed to compensate for the shrinkage of the whole casting.
    [Show full text]
  • Channel Structures Formed in Copper Ingots Upon Melting and Evaporation by a High-Power Electron Beam
    Metals 2015, 5, 428-438; doi:10.3390/met5010428 OPEN ACCESS metals ISSN 2075-4701 www.mdpi.com/journal/metals/ Communication Channel Structures Formed in Copper Ingots upon Melting and Evaporation by a High-Power Electron Beam Sergey Bardakhanov 1,2,5, Andrey Nomoev 2,3,*, Makoto Schreiber 2, Alexander Radnaev 2, Rustam Salimov 4, Konstantin Zobov 1,5, Alexey Zavjalov 1,5 and Erzhena Khartaeva 2,3 1 Khristianovich Institute of Applied and Theoretical Mechanics, Siberian Branch of the Russian Academy of Sciences, Institutskaya str., 4/1, Novosibirsk 630090, Russia; E-Mails: [email protected] (S.B.); [email protected] (K.Z.); [email protected] (A.Z.) 2 Department of Physics and Engineering, Buryat State University, Smolina str., 24a, Ulan-Ude 670000, Russia; E-Mails: [email protected] (M.S.); [email protected] (A.R.); [email protected] (E.K.) 3 Institute of Physical Materials, Siberian Branch of the Russian Academy of Sciences, Sakhyanovoy str., 6, Ulan-Ude 670047, Russia 4 Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Lavrenteva str., 11, Novosibirsk 630090, Russia; E-Mail: [email protected] 5 Department of Physics, Novosibirsk State University, Pirogova str., 20, Novosibirsk 630090, Russia * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +8-902-564-24-62. Academic Editor: Hugo F. Lopez Received: 5 November 2014 / Accepted: 5 March 2015 / Published: 12 March 2015 Abstract: A new phenomenon is described in this paper: the formation of macroscopic channel structures on the bottom of copper ingots which were used as the target for the synthesis of copper nanoparticles by high-power electron beam evaporation and condensation.
    [Show full text]