1 Metals (RWTRM pages 55 – 63) Types of Materials Candidates should be able to: show a working knowledge of the following metals: ferrous metals (mild and high carbon steels); non-ferrous metals (aluminium, duralumin and other common casting alloys, copper and its alloys, zinc, lead and tin All metals can be classified as either Ferrous or Non-ferrous. Ferrous metals are those which contain iron. They may have small amounts of other metals or other elements added, to give the required properties. All ferrous metals are magnetic and give little resistance to corrosion Non-Ferrous Metals are those which do not contain any iron. They are not magnetic and are usually more resistant to corrosion than ferrous metals. Resistant Materials

2 Metals Pure Metal only consists of a single element. This means that it only has one type of atom in it. The common pure metals are:-aluminium, copper, iron, lead, zinc, tin, silver and gold. Alloys are a mixture of two or more metals. When a material is needed which requires certain properties and this does not exist in a pure metal we combine metals. Pure white aluminium is very soft and ductile. Other elements can be added to create an aluminium alloy. This can produce a metal which is stronger than Mild Steel, has improved hardness and is resistant to corrosion while still remaining light in weight. Resistant Materials

3 Ferrous metals Mild Steel Composition Fe, 0.15%-0.35%C Photo: Hinge, nail, screw and washer. Use: General structural work, girders, nuts, bolts, screws, non cutting tools and car bodies. Note: Tinplate is mild steel coated in tin. Galvanised sheet is mild steel coated in zinc. Terne plate is mild steel coated in lead. Stainless Steel Composition Fe, C, 18%Cr, Ni, Mn Photo: Cooking Oil Drizzler. Uses: Sink units, kitchenware, pipes and aircraft. Note: Stainless steel has a high tensile strength and resists abrasion and corrosion because of its high chromium content. It is difficult to cut or file. Resistant Materials

4 Ferrous metals Medium Carbon Steel Composition Fe, % C Photo: Rear sprocket on a mountain bike. Uses: Garden tools, wire ropes, axles and shafts. Note: Medium Carbon Steel is less ductile and malleable than mild steel. High Carbon Steel Composition Fe, % C Photo: Plane blade, screwdriver and wood chisel. Uses: Hand tools, chisels, screwdrivers and punches. Note: The strength of High Carbon Steel decreases when it contains more than 0.9% carbon. Hardness and toughness can be improved by heat treatment. High Carbon Steel is not as malleable and ductile as mild steel. Silver steel is an example of high carbon steel. Also known as Tool Steel. Resistant Materials

5 Ferrous metals High Speed Steel Composition Fe, % C, W, Cr, V. Photo: Milling cutters. Uses: Cutting tools for lathes, milling cutters and drill bits. Note: High Speed Steel can be hardened and tempered. Will retain hardness up to temperatures of 600°C. Also known as Tool Steel. Cast Iron Composition Fe, 3.5% C Photo: Cast Iron drain grill. Uses: Cylinder blocks, piston rings, car brake drums, vices, manhole covers, fire grates and machine tools. Note: Cast Iron has a high fluidity when casting. It has a hard skin but soft core and is strong in compression. Resistant Materials

6 Non Ferrous Metals Tin Composition Pure Metal Melting point 232°C Photo: Tinplate food cans. Uses: Soft solder, alloys (a major part of pewter). Note: Tin is very soft (only slightly harder than lead) and malleable; it can be rolled, pressed, or hammered into extremely thin sheets (tin foil). When iron or sheet steel is dipped into molten tin (tinplate), a layer of tin is deposited on the surface. A tin coating may also be applied by electroplating, which uses less tin. The tin serves to prevent rusting as it is barely affected by moisture. Resistant Materials

7 Non Ferrous Metals Aluminium Composition Pure metal Melting point 660°C Photo: Spun aluminium saucepan. Uses: Car bodies, cookware, food wrapping foil, insulation, aircraft, boats, engine cylinder heads and window frames. Note: Aluminium is rarely used as a pure metal. It is mainly alloyed with copper to improve strength, eg. Duralumin which is used in the production of aircraft parts. Copper Composition Pure metal Melting point 1080°C Photo: Water pipe fittings Uses: Electrical wire, printed circuit board, central heating pipe, boxes, bowls and rivets. Note: Copper is malleable, ductile and only silver and gold have higher values of conductivity. It can be enamelled. Copper roofs become tarnished by the atmosphere resulting in a green patina known as verdigris. Resistant Materials

8 Non Ferrous Metals Photo: Cast candle stick Uses: Castings, boat fittings, ornaments, wood screws and cartridge cases. Note: Brass is an alloy of mainly copper and zinc with small amounts of other metals. It can be forged or hammered into various shapes, rolled into thin sheets, drawn into wires, machined and cast. Bronze Composition Cu, Sn and others Melting point °C Photo: Lost wax casting of a sculpture. Uses: Bearings, gears, statues, coins, pumps and springs. Note: Bronze is an alloy of copper, tin, zinc, phosphorus, small amounts of other elements. Bronze is harder than brass. Types available include: Aluminum Bronze, Bell Metal, Gun Metal, Manganese Bronze, Phosphor Bronze. Resistant Materials

9 Non Ferrous Metals Zinc Composition Pure Metal Melting point 400°C Photo: Model car die casting in 'Mazak' a zinc die casting alloy. Uses: Galvanised steel buckets, tanks and dustbins and rust proof paints. Note: Zinc is brittle and crystalline at ordinary temperatures, but when heated to between 110°C and 150°C it becomes ductile and malleable; it can then be rolled into sheets. Although it is not abundant in nature, it is of great commercial importance. It is used principally for galvanizing steel, but is also important in the preparation of certain alloys such as brass and bronze. Can be used to produce intricate (but brittle) castings. Photo: Roof flashing. Uses: Car batteries, protection against X-rays and radiation, paints, roof flashing and alloying. Note: Lead is a dense, relatively soft, malleable metal with low tensile strength. It is a poor conductor of electricity and heat compared to other metals such as copper. Lead poisoning can occur when organic compounds containing Lead enter the body by respiration (of dust, fumes, or sprays) or by ingestion of food or other substances that contain lead. Lead Composition Pure Metal Melting point 327°C Resistant Materials

10 Definitions of properties of Materials. HardnessThe resistance a materials has to cutting and surface indentations. Toughness This describes the amount of energy a material can absorb without breaking. This is the opposite to brittleness. We measure a material's ability to absorb shock. Tensile Strength The maximum force a material can withstand in tension (pulling) compression (squashing), torque (twisting) and shearing (sideways pressure). Malleability The amount of hammering, pressing and shaping a material can take without breaking. DuctilityThe length that a material can be stretched without breaking. Elasticity The length that a material can be stretched and return to its original length when released. Heat and Electrical Conductivity The measure of how well a material can conduct heat or electricity. Heaviness The denseness of materials. A dense material will be heavy in relation to its size. StrengthThe measure of how a material withstands a heavy load without breaking. Resistant Materials

11 Properties of ferrous metals NameCompositionPropertiesUses Mild Steel0.15 to0.30% carbon girders, Plates, nuts and bolts, general purpose. High Speed Steelmedium carbon, tungsten, chromium and vanadium. Cutting tools for lathes. Stainless Steel18% chromium, and 8% nickel added. Kitchen draining boards. Pipes, cutlery, aircraft. High Tensile Steel Low carbon steel,, nickel,and chromium. Gears, shafts, engine parts. High Carbon Steel 0.70% to 1.40% carbon. Chisels, hammers, drills, files, lathe tools, taps and dies. Medium Carbon Steels 0.30% to 0.70% carbon. Metal ropes, wire, garden tools, springs. Cast Iron Remelted pig iron with small amounts of scrap steel. Heavy crushing machinery. Car cylinder blocks, vices, machine tool parts, brake drums, machine handle and gear wheels, plumbing fitments. Complete the chart below by entering the properties of each material. Resistant Materials

12 Properties of non ferrous metals Complete the chart below by entering the properties of each material. NameCompositionPropertiesUses AluminiumPure MetalAircraft, boats, window frames, saucepans, packaging and insulation, pistons and cranks. Aluminium alloys- Duraluminium) Aluminium +4% Copper+1%Mang anese Aircraft and vehicle parts. CopperPure metalElectrical wire, cables and conductors, water and central heating pipes and cylinders. Printed circuit boards, roofs. Brass65% copper +35%zinc. Castings, ornaments, valves,forgings. LeadPure metalProtection against X-Ray machines. Paints, roof coverings, flashings. ZincPure metalMakes brass. Coating for steel galvanized corrugated iron roofing, tanks, buckets, rust- proof paints TinPure metalTinplate, making bronze. Gilding metal 85% copper+15% zinc. Beaten metalwork, jewellery Resistant Materials

13 1. Which type of Ferrous metal would be suitable to make tough kitchen sink units from? The surface would have to withstand shocks and wear and water flooding. 2. Name the Ferrous metal that most work-shop tools are made from? 3. Give an example of a suitable ferrous metal that may be used to make garden tools? 4. Why are the majority of wire electrical cables made from copper? 5. Name a Non-ferrous metal that is used to protect dental nurses, doctors and dentists from the harmful radiation that is given off when using X-rays? 6. How are steel corrugated roofs made water resistant? 7. Why are the panels of Land-Rovers made from Aluminium? 8. Name a Non-Ferrous metal that is suitable to make ornaments ? Name the industrial process used? 9. Give the name of the metal that is suitable to make jewellery from? Why is it a good choice? 10. Why is High tensile steel an ideal metal to make car gears from? Resistant Materials