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INDUSTRIAL MATERIALS INTRODUCTION Industrial materials are substances employed in industrial processes for the creation of goods and artifacts. Materials may be classified in different ways: nature of constituents, usage, etc. In general, they are classified as metals and non-metals. Most metals are solids at room temperature and exist as crystal lattices with atoms held together by strong metallic bonds. Metals are grouped into ferrous and non-ferrous materials. Metals can further be classified as plain or alloy metals. Plain metals are materials that have a significant composition of a base element but contain traces of other elements mainly as impurities. Alloy metals are materials that have one or more base elements but contain significant amount of other elements that are used to impact specific properties. That is, for some metals, mechanical, chemical, electrical, etc., properties can be modified by adding alloys. An alloy is an element added to a base material so as to modify the properties of the base material. An alloyed material is a uniform mixture of the base and alloying substances. Metals usually have high melting point, are relatively ductile and malleable, and are hard with relatively high tensile strength. They are often good conductors of heat and electricity with high densities. Exceptions include mercury which is liquid at room temperature with a melting point of -39 oC. Sodium and potassium are light and soft with melting points of 97 oC and 63 oC respectively.

Metals are used in two forms of castings and wrought metals. Casting is used to produce ingots or component blanks. The component blanks or workpieces are processed into finished forms by secondary manufacturing processes. Ingots are used as stock materials for producing wrought metals which are obtained by some secondary manufacturing processes such as forging, rolling, and extrusion. Practically all metals, which are not used in cast form or component blank, are reduced to some standard shapes for subsequent processing. Ingots are obtained by casting liquid metal into rectangular and square cross-sections. The section may be in form of a slab, billet, or bloom. Sometimes continuous casting methods are also used to cast the liquid metal into slabs, billets or blooms. Slabs measure 500-1800 mm wide and 50-300 mm thick. Billets measure 40x40 to 150x150 sq. mm, and blooms measure 150x150 to 400x400 sq. mm. These shapes are further processed through hot rolling, forging or extrusion, to produce materials in standard form such as plates, sheets, rods, tubes and structural sections.

Non-metals exist as covalent molecules where atoms are held together by weak forces. Non-metals usually have low melting point, are relatively brittle and soft with relatively low tensile strength. They are often bad conductors of heat and electricity with low densities. Exceptions include which is extremely hard with high melting temperature when in the form of diamond and is a good conductor of heat and electricity when in the form of graphite.

FERROUS MATERIALS Ferrous materials have as base or main constituent. They include iron, steel and their alloys. For example, pig iron has iron content of 91% to 99% and carbon content of 3.5% to 4.5%. has iron content of 98.1% to 99.5% and carbon content of 0.07% to 1.5%. has iron content of 99% to 99.8% and carbon content of 0.05% to 0.25%. These materials usually have some traces of , surphur, phosphorus, and .

Cast Iron Ferrous iron materials include pig iron, , and wrought iron. Cast iron can further be classified into gray cast iron, white cast iron, chilled cast iron, ductile cast iron, and malleable cast iron. Pig iron is a very brittle material and it is further processed to make it useful as a structural material. Generally, cast iron materials are suitable in situations where components are under compressive loads. They are not good in resisting dynamic and tensile loads. However, ductile cast iron is better in resisting tensile and dynamic loads compared to other types. It is to be noted that malleable cast as a structural material is being supplanted by ductile cast iron which is easier to produce. Table 1 summarizes cast iron materials and applications.

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Table 1: Iron materials Iron Type Carbon Applications Content (%) Pig iron ≥3 Raw material for cast iron and steel manufacture. Produced as ingots in the form of slabs, billets, and blooms. Plain cast iron. Hard and brittle. Good for cast products. Used for Gray cast iron 2- 4 machine beds and frames, cylinder blocks, agricultural implements, etc. Plain cast iron. Hard and brittle. Good for cast products where White cast iron high wear resistance is important. Plain cast iron. Hard and brittle. Extremely hard surface, e.g. car Chilled cast iron wheels, furnace firebars, and rolls for rolling mills. Alloy cast iron from heat-treated white cast iron. Easily machined Malleable cast and shock resistant. Used for pipe fittings, gears, housings for ball iron and roller bearings, agricultural and mining equipment, etc. Alloy cast iron that is specially produced. Is relatively ductile and Ductile cast iron has better shock resistance to malleable cast iron. Used for crankshafts, anvils, wrenches, or heavy-use levers Purest form of commercial iron. It is ductile, tough, malleable, and easy to weld. Formerly used for making rivets, nails, chains, Wrought iron ≤ 0.1 railway couplings, horse-shoes, etc.

Steels Steel is a material consisting mainly of iron (Fe) and iron carbide (Fe 3C) or . The carbon content is at most 2% and it can contain other elements and alloys in controlled amounts. It is produced mainly from pig iron (about 90% of pig iron is converted to steel) by oxidation which reduces the carbon content and removes impurities in pig iron. It is a hard, tough, and strong material. Properties of steel depend on its carbon content, alloys, and heat treatment given to it.

Table 2: Steel materials Steel Type Designation* Principal Mechanical Properties Common Applications Carbon Steels Low Carbon 1005 - 1025 High toughness and ductility, low Pressed steel products, chains, Medium(0.05 – 0.25) Carbon 1025 – 1050 strength.Medium toughness and ductility, Medium Machinerivets. parts, gears, axles, High(0.25 Carbon– 0.50) 1050 & over strength.Low toughness and ductility, high Cuttingforgings, bolts tools, and music nuts. wires, Alloy(0.50 –Steels 1.50) strength. springs. Sulfurized (Free- 11XX Improved machinability Machined parts, threads, cutting) splin es. Higher strength and hardness, lower Phosphorized 12XX ductility. Manganese 13XX Improved surface finish Mechanical parts, axles, gears, Molybdenum 40XX - 48XX High strength cams, forgings. Improved hardness, great strength and Gears, shafts, bearings, 50XX – 50XX toughness. springs, connecting rods. Chromium- Punches, dies, piston rods, 61XX Improved hardness and strength Vanadium gears, axles. Nickel- High corrosion resistance, high strength Food containers, surgical Chromium- 86XX – 88XX and hardness. equipment. Molybdenum Silicon- 92XX High springiness and elasticity. Springs. Manganese

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Generally, tensile strength of steel increases with higher carbon content but the steel loses ductility, becoming brittle. Steel of appropriate carbon content may be hardened and annealed or tempered. Hardening is the process of cooling steel of high temperature (red hot) rapidly so as to increase its hardness. Annealing is the process of reheating hardened steel to elevated temperature and allowing it to cool in air. Annealing is generally employed when hardened steel needs machining. is the process of reheating hardened steel to elevated temperature and allowing it to cool. The hardness and tensile strength of steel depends on the tempering temperature and rate of cooling.

Table 3: UNS classification of materials (e.g. SAE/AISI1025 = G10250) UNS Series Material Non-ferrous Metals and Alloys A00001 to A99999 Aluminum and alloys C00001 to C99999 Copper and alloys L00001 to L99999 Low-melting metals and alloys Z00001 to Z99999 Zinc and alloys Ferrous Metals and Alloys D00001 to D99999 Specified mechanical properties of steel materials F00001 to F99999 Cast G00001 to G99999 AISI and SAE carbon and alloy steels, excluding tool steels H00001 to H99999 AISI H-classification steels J00001 to J99999 Cast steels, excluding tool steels K00001 to K99999 Miscellaneous steels and ferrous alloys S00001 to S99999 Stainless steels T00001 to T99999 Tool steels

Table 4: Carbon steel types and applications Plain Carbon Carbon (%) Stock Form Processing and Applications Steel Type Stock available in black and Easily worked when hot but difficult to machine low 0.05 – 0.15 bright bars, tubes, and wires. due to tendency to tear. Rivets, screws, nails, wires, chains, pipes, boiler plates. Stock is available in black Cheapest type of steel. Easily machined and bar and sheet section or welded. Ship plates, forgings, gears, shafts, bolts, Mild 0.15 – 0.25 bright strip, and tube nuts, washers, rivets, chains. sections. Stock is available in black Can be machined satisfactorily. Responds to heat- bar, plate, and sheet section treatment. Machine parts and forgings, castings, Medium 0.25 – 0.50 or bright rod, strip, and flats springs, drop hammer dies. sections. Harmers, sledges, stamping and pressing dies, 0.5 – 0.7 drop-forging dies, screwdrivers, set-crews. Punches, cold chisel, hammers, shear blades, drop- 0.7 – 0.8 Machining and forming forging dies, lathe centers, spanners, band saws, difficulties increase with vice jaws, rivets. carbon content. Stock Punches, cold chisel, hammers, shear blades, drop- High available in bars and strips. forging dies, lathe centers, spanners, saws, vice 0.8 – 1.0 steel rods available jaws, rivets, springs, axes, rock drills, milling too. cutters, lathe centers, reamers, screw dies and taps. Drills, milling cutters, lathe tools, files, wire 1.0 – 1.5 drawing dies, hacksaw blades, ball bearings, screw dies and taps.

Steel materials may be broadly classified into plain and alloy steels. Plain steel has carbon as main alloy in an iron base. Plain steels may be grouped into cast steel, carbon steels, and carbon tool steels. has other elements in significant quantities and they include chromium, nickel, surphur, etc. These elements are deliberately added to steel so as to impact specific properties desired. Alloy steels include low, high, and

3 Osakue alloy tool steels. Table 4 is a summary of the different types of steels and typical applications. Table 5 summarizes common alloy elements and their effects on steel.

Table 5: Effects of alloying elements on steels Alloy Content (%) Effect Along with nickel and or molybdenum, increases hardness and tensile strength 0.3 - 1.5 Chromium with considerable ductility. Enhances corrosion and wear resistances. High values 12 - 20 Improves fatigue resistance. 5 – 10 Retention of hardness at high temperature. Cobalt 12 – 18 Increased corrosion resistance in . ≤ 40 Improves coercive force of magnetism in some steels. 1.5 – 5 Increases tensile strength and toughness. Nickel ≥ 20 Increases corrosion and heat resistance. Strengthens steel at normal and high temperature. Greatly improves hardness of Tungsten steel. Improves resistance to sulphuric and other acids in stainless steels. Helps steel to Molybdenum 0.08 – 0.4 retain strength and hardness at elevated temperature. Silicon 1.8 – 2.2 Improves springiness and elasticity. Sulphur Improves machinability. Phosphorous Increases strength and hardness but reduces ductility. Manganese 1.6 – 1.9 Improves surface finish, shock and wear resistance. Vanadium Increases hardenability, toughness, and strength. Titanium Tantalum Prevents weld decay in chromium and nickel stainless steels. Niobium Boron 0.003 Greatly improves hardenability. Copper 0.2 – 1.0 Improves corrosion resistance.

PLAIN NON-FERROUS METALS The common non-ferrous metals are copper, zinc, tin, lead, and aluminum. Others are tungsten, vanadium, chromium, magnesium and manganese.

NON-FERROUS ALLOYS Non-ferrous alloys contain non-ferrous metals as base materials with alloying elements that may be ferrous or non-ferrous. They generally exhibit better mechanical properties than the plain materials. The popular non-ferrous alloys include brasses, bronzes, magnesium alloys and solders.

PLASTICS Plastics are solid materials that are mainly hydrocarbon (hydrogen and carbon) or organic compounds. They consist of long chains of simple molecules fused together by a process called polymerization. During polymerization, simple hydrocarbon molecules are replicated and linked together to form heavier and more complex hydrocarbon molecules. Hence they are also called polymers. As a rule of thumb, a polymer must contain at least 10 simple organic molecules. The complex molecules from polymerization have physical properties usually different from the original molecules. They are capable of retaining their shape and form under ordinary conditions. Plastics are manufactured mainly from products of crude oil and natural gas. Plastics may be grouped into thermoplastics, thermosets, and elastomers.

Thermoplastics : Thermoplastics are the set of plastics that soften and melt when heat is applied. They have straight or branched chains of molecules joined by weak forces. They harden when cooled and are capable of being re-shaped or re-molded several times. Examples include acrylic, ABS, Nylons, Polyethylene, PVC, etc.

Thermosetting Plastics : Thermosetting plastics or thermosets are the set of plastics that do not soften and melt when heat is applied. They have chains of molecules in 3-D layout that are joined by strong forces.

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They are formed by the application of both heat and pressure. They harden when heated and cannot be re- shaped or re-molded several times. Examples are polyester, phenolics, polyimides, etc.

Elastomers : Elastomers are plastics with high elasticity. They undergo considerable elongation under load and return to their original shape and size when unloaded. Examples are rubber, silicones, polyurethanes, etc.

WOOD Wood is composed of cellulose bonded by lignin and the cellulose is longitudinal in orientation. Wood contains about 50% - 60% cellulose and 20% - 35% lignin with other constituents in small amounts. These other constituents include resins, pentosane, carbohydrates, gum, and mineral water. The cellulose is the structural substance in wood and is hollow with very small diameter. Wood may be classified into softwood and hardwood. Softwood products are generally used for structural applications in the United States.

Softwood : Softwoods are derived from coniferous trees which have needle like leaves. The dimensions of softwood lumber are standardized with the actual sizes are generally less that the nominal sizes. Softwood products are mainly used for building construction and decorative works. Examples of softwood sources are pine, cedar, spruce, fir, and redwood. Pine wood is used in building construction, furniture work, boxes, and molds for manufacturing processes. Cedar wood is used in making closets, chests, planks, and blinds for windows. Spruce wood is used in making boxes, crates, ladders, ship masks, aircraft parts. Fir wood is used in furniture, windows, doors, and frames for windows and doors. Redwood material is used in flooring houses, panels, and fences.

Hardwood : Hardwood is obtained from deciduous trees which shed their leaves at the end of each growing season. Most hard wood materials are strong, durable, and experience minimum shrinkage or warping with age. They are primarily used for furniture and cabinet works. Examples of hardwood sources are oak, walnut, mahogany, cherry, maple, and teak. Oak is used for desks, flooring, and boat frames. Walnut and mahogany are used for desks, tables, and cabinet. Cherry is used for cabinets, door handles, and boats. Maple is used for flooring and bowling alleys. Teak is used for flooring, in shipbuilding, window and door frames.

CERAMICS Ceramics are inorganic compounds that contain metals and non-metals. They are corrosion resistant and very hard. However, they are brittle and have low impact strength. Clay-based ceramic products include bricks, tiles, clay pipes, porcelain, stoneware, and earthware. Fire clay, a common refractory material, is designed to resist high temperatures. Ceramics may be grouped as oxides, nitrides, carbides, and glasses.

COMPOSITES Composites have two or more constituents that are blended and held together by mechanical or adhesive bonding. The constituent materials are usually distinct in chemical properties. Composites are referred to as engineered materials because they are designed and manufactured to desired application qualities. Composites can be a combination of metals, plastics, ceramics, fibers, etc. In composites, a filler material or filler materials are dispersed in a matrix or base material so that the filler(s) reinforce the matrix. Usually fillers are made from strong and stiff materials while the matrix has low density. The properties of the composite are better than the properties of individual constituent. Typically, the fillers carry the load while being held in place by the matrix. The fillers or reinforcements impart their special mechanical and physical properties to enhance the matrix properties. The number of composite materials is increasing rapidly and so are their applications. Composite materials are used to make consumer and recreation products, components for bicycles, vehicles, and aircrafts, electrical products, and products for building construction and industrial facilities. Composites have high strength to weight ratio, can resist fatigue damage better that steel or aluminum, have high wear resistance, and can be formulated to provide high toughness and damping. Composites may be classified into fiber-reinforced, particulates, and laminates, based on the filler type. Another classification approach uses the matrix material type: polymer, metal, and ceramic matrix composites.

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Table 6: Some materials and properties Young’s Modulus Yield Strength Tensile Strength % Elongation (50 Material (GPa) (MPa) (MPa) mm length) Metals Aluminum & alloys 69 - 79 35 - 550 90 – 600 45 - 4 Copper & alloys 105 – 150 76 - 1100 140 - 1310 65 – 3 Lead & alloys 14 14 20 - 55 50 – 9 Magnesium & alloys 41 - 45 130 - 305 240 - 380 21 - 5 Molybdenum & alloys 330 - 360 80 - 2070 90 - 2340 40 – 30 Nickel & alloys 180 - 214 105 - 1200 345 - 1450 60 – 5 Steels 190 - 210 205 -1725 415 - 1750 65 – 2 Titanium & alloys 80 -130 344 - 1380 415 - 1450 25 – 7 Tungsten & alloys 350 - 400 550 - 690 620 - 760 0 Non-Metals Ceramics 70 - 1000 - 140 - 2600 0 Diamond 820 - 1050 - - - Glass & porcelain 70 - 80 - 140 0 Rubbers 0.01 - 0.1 - - 1000 – 5 Thermoplastics 1.4 – 3.4 - 7 - 80 - Thermoplastics, 2 - 50 - 20 - 120 10 -1 reinforced Thermosets 3.5 - 17 - 35 - 170 0 Boron fibers 380 - 3500 0 Carbon fibers 275 - 415 - 2000 - 3000 0 Glass fibers 73 - 85 - 3500 - 4600 0 Kevlar fibers 62 - 117 - 2800 0

Summary Industrial materials are substances employed in industrial processes for the creation of goods and artifacts. Materials may be classified in different ways: nature of constituents, usage, etc. In general, they are classified as metals and non-metals. Metals are of two groups: ferrous and non-ferrous materials. Ferrous materials include Iron (Pig, Wrought, Cast); plain carbon steels (Low, Medium, High); and alloy steels (Stainless, Tool, etc). Non-ferrous materials include plain (Aluminum, Copper, Titanium, Nickel, Tungsten, etc) and alloys (Brass, Bronze, etc). Non-metals include plastics, wood, ceramics, composites, and miscellaneous. Plastics are of three parts: thermoplastics (Acrylic, ABS, Nylons, Polyethylene, PVC, etc); thermosetting (Epoxies, Phenolics, Polyimides, etc); and elastomers (Rubber, Silicones, Polyurethanes, etc). Woods are classified into two groups of hardwood and softwood. Ceramics may be grouped into oxides, nitrides, carbides, and glasses. Composite materials include fiber-reinforced, particulates, and laminates. Miscellaneous materials include fabrics, leather, and paper. Table 16 presents a summary of some materials.

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