Material Science Metals

Metallic Materials Metallic materials have a wide range of properties, pure metallic materials have quite limited commercial use Metal alloys, which are combinations of at least two elements, are far more versatile and for this reason are the form in which more metals are produced and used by industry In general, they are classified into two broad families – ferrous and non-ferrous

Ferrous Materials The type of steel depends on two factors: The carbon content The alloy element

Classification of Ferrous Materials High Speed Steel

Plain Carbon Steel Divided into 3 categories: Low Carbon Steel : up to 0.3% carbon Medium Carbon Steel : 0.3 – 0.6% carbon High Carbon Steel : 0.6 – 1.4% carbon

Low Carbon Steel Plain Carbon Steel The hardness of a steel is increased by the addition of the carbon Since the proportion of carbon is low the hardness figure is low These materials normally have good ductility and are easily worked Steel with carbon content between 0.15 and 0.3% are called mild steel This is a very common steel extensively used throughout industrial

Low Carbon Steel Plain Carbon Steel Application: Rivet, wire, nail, chain, seam-welded pipes, I-beam, U-channel, angle iron, sheet and plate, Levers, shafts

Medium Carbon Steel Plain Carbon Steel Since the carbon content is increased, the hardness of the steel also increases This increase means that the material loses some of its ductility It is offset by an increase in strength The hardness can be increased by ‘Heat treatment’ It is also called ‘Yellow label steel’

Medium Carbon Steel Plain Carbon Steel Application: Shafts, connecting rods, crane hooks Gears, crankshaft Rails, wire rope, leaf spring

High Carbon Steel Plain Carbon Steel Since the carbon content is very the steel is much harder Further degree of hardness can be achieved by heat treatment Used extensively in the manufacture of hand and machine cutting tools

High Carbon Steel Plain Carbon Steel Application: Dies, saw blades, anvil faces Chisels, punches, shear blades Drills, lathe tools, taps, reamers

Stainless Steel Alloy Steel Stainless Steels contain a minimum of about 12% Chromium, which permits a thin, protective surface layer of chromium oxide to form when steel is exposed to oxygen. The addition of chromium and sometimes nickel to the steel greatly improves the resistance to corrosion. The ’18-8’ stainless steel often refers to a steel having about 18% chromium and 8% nickel

Stainless Steel Alloy Steel Application: Wire, tubing, sheets Surgical and dental instrument Poppet valves for internal-combustion engines, turbine blades, pump shafts Chemical, dairy, laundry, and oil equipment

High Speed Steel Alloy Steel High Speed Steel (HSS) designates a number of steels that have several properties which enhance their value as cutting tool material They can be hardened to a hardness ranging from 63 Rc to 70 Rc The principal alloying elements of HSS are tungsten, molybdenum, chromium, vanadium and carbon HSS can be used for cutting tools such as drills, reamers, taps, dies, milling and turning cutters

Cast Irons The carbon content of CI is between 2 – 4% It is hard and brittle When molten it has good fluidity, producing good component features It is rigid and has very good compressive strength

White Cast Irons Cast Iron It is given the name because the appearance of a fracture surface is bright and silvery It is very hard with good strength but there is a tendency to brittleness Very difficult to machine Its most common applications are grinding mill part, rolls for cement, ceramic and mining industrial and as a basis when producing malleable irons

Grey Cast Irons Cast Iron It is given the name because the appearance of a fracture surface is dull grey It is softer with a lower tensile strength Grey irons are very strong in compression and also absorb vibration It has low point and with good fluidity giving good casting properties Good machinability Typical applications are cylinder blocks for cars, machine tool beds, wheel drum, industrial furnace parts, water pipes and pistons

Copper Non-ferrous metal Copper is a material which has been used for thousands of years It can be used as pure metal or in combination with other elements as an alloy The pure metal possesses desirable properties: High electrical conductivity High thermal conductivity High ductility Good malleability High corrosion resistance Typical applications are conductors, electrical components, tubing, wire, sheet, electrodes

Brass Non-ferrous metal Brass is an alloy of copper and zinc but also contain small amounts of other alloying elements 70/30 brass, because of its ductility, can be used in pressing and drawing operations, and is used for condenser tubes 60/40 brass is used where the material is to be hot-worked. It is ideal for producing hot stampings and extruded bars, rods and sections High tensile brass, is basically a 60/40 brass with additional alloying elements such as tin, iron and aluminium. This material can be cast, forged, and extruded. Uses include valves, pumps, propellers, screws

Bronze Non-ferrous metal Bronze is essentially an alloy of copper and tin, but also contain additional elements such as zinc and phosphorus Bronze with 5% tin and 0.4% phosphorus, it has good elastic properties and is used for springs Bronze with 10% tin and 0.5% phosphorus, it is used for bearing applications Bronze with 10% tin and 2% zinc, is largely used for naval purposes – valves, pump bodies, and fittings of water and steam

Aluminium and its alloys Non-ferrous metal Light metal, having approximately 1/3 of the density of steel The oxide film gives excellent corrosion resistance High thermal and electrical conductivity High malleability, possible to produce very thin foil Major disadvantage: lack of strength To overcome the problem aluminium is therefore alloyed with magnesium, manganese, copper, silicon and tin Increase the strength and hardness and enables the material to be heat-treated to give additional properities

Aluminium and its alloys Non-ferrous metal Applications: Plate, tube, wire, bars, extruded sections Floor section, superstructure of hovercraft, variety of components in aircraft Large and small cable, foil, strip winding for coil and transformer Roofing and structural applications, door and window frame, decorative items Watches, photographic equipment, component for machine tools Pans, furniture, packaging uses for food and drink

Magnesium and its alloys Non-ferrous metal Density is approximately 2/3 of aluminium Highly reactive when contact with oxygen Weak and unsuitable for general use, so alloys are formed aluminium and zinc are commonly added After alloying, obtained a high strength-weight ratio Its most important applications are in the aircraft industrial or other areas where weight is a limiting factor Can be supplied in a number of forms: sand or die-cast, forged, extruded, rolled in sheet or plate Typical applications: wheels for racing cars, crankcase and gearbox for aircraft and cars, airframe components, camera cases, business machines

Lead Non-ferrous metal Lead in its pure state is very soft and has low mechanical strength High corrosion resistance, widely used in chemical industrial Used for radiation shielding Two of its largest uses are as cable sheaths for power cables and in the manufacture of connectors and grids in lead-acid batteries Lead-tin alloys give a range of soft solders

Zinc Non-ferrous metal Its largest single use is as a zinc coating (galvanizing) on iron and steel. Zinc alloy containing 4% aluminium is most widely used for die-casting alloys The low cost and low melting point of zinc alloys make them especially suitable for die-cast parts Their excellent castability allows production of smooth-surface Machinability is good, but zinc alloys are difficult to weld and solder. Uses include the mass production of car parts, camera parts, power tools, clock parts and domestic appliances

Tin Non-ferrous metal Tin is a white or silvery metal with a density close to that of steel. Commercially pure tin is rarely used alone except as a coating material. Tin with the addition of 0.4% copper is used as foil and for collapsible tubes. The major use of tin and its alloys is in corrosion-resistant products. More than 40% of the world's tin is used as a coating for steels and copper. Tinfoil is used for liners for bottle caps and electrical condensers. Heavy-walled tin pipe and tin-lined copper pipe is used in the food and beverage industries. And, tin wire is used for electrical fuses and for packing glands in pumps of food machinery. Alloys of tin and lead are used extensively as solders