Metals Design and Manufacture

Metals Produced by mining ore from the Earth Three main categories of metal: ▫Ferrous ▫Non ferrous ▫Alloys Available in a wide variety of sections: ▫Round, square, flat bar or square tube Sold in imperial sizes

Properties of metals Elasticity – regain original shape after being deformed Ductility – stretch without breaking Malleability – ability to be easily pressed, spread and hammered into shapes Hardness - resistance to scratching, cutting and wear Work hardness – structure of metal changes as a result of repeated hammering or strain. Brittleness – break without bending Toughness – resistance to breaking, bending or deforming Tensile strength – strong when stretched Compressive strength – strong under pressure

Metals Ferrous metals: ▫Contain iron ▫Prone to rusting if exposed to moisture ▫Can be picked up by a magnet Non Ferrous metals: ▫No iron content ▫Do not rust Alloys ▫Contains two or more metals to improve properties ▫Carefully chosen and mixed to achieve specific properties.

Ferrous metals NameDescriptionUses Mild steelDuctile and malleable, rusts quickly when exposed Nuts, bolts, car bodies, gates, girders Cast ironVery strong in compression but brittle Metal work vices, brake discs, manhole and drain covers Tool steelStrong and very hardHand tools – chisels, screwdrivers, hammers, saws Stainless steelResistant to wear and corrosionKitchen sinks, cutlery, dishes, teapots High speed steelBrittle but resistant to wearDrill bits, lathe tools, milling cutters. Where high speeds and temperatures are created.

Non ferrous metals NameDescriptionColourUses AluminiumLight in weightLight grey in colourCooking foil, saucepans, cans, window frames CopperDuctile and malleable. Excellent conductor of heat and electricity Reddish-brown metal Plumbing and electrical components. TinDuctile. Resistant to corrosion, malleable Bright silverCoating on food cans and similar packaging ZincWeak metal, resistant to corrosion SiverCoating on steel buckets, screws

Alloys NameDescriptionColouruses BrassHard metal, mixture of copper 65% and zinc 35% YellowDecorative metal work – door handles, candlesticks PewterLead free alloy. Easily cast. Mainly tin and small amounts of antimony and copper Bright mirror affect finish Drinking tankards, jewellery, picture frames Casting alloyAluminium 3% and silicon 5% SilverEngine components

Metal Processes Design and Manufacture

Joining and shaping Methods in Metal Brazing Soldering Riveting Welding

Joining of metals Welding: soldering, brazing and welding techniques used mainly to join metals. ▫Arc welding – heat obtained by electric arc via transformer. One lead is attached to work and other to grip holding welding rod. Arc is formed when end of rod is brought near work. Heat melts parent metal and filler rod together. ▫Spot welding – metal is heated and fused together between two copper electrodes. Used on thin gauge mild steel Nuts and bolts – thread has the advantage to be taken apart for inspection or maintenance. Can be obtained in various forms.

Pop Riveting Pop riveting is a technique that is used to join thin pieces of metal or plastic sheets together. The rivet has two parts:  the pin and the rivet. The pop rivet pliers are used to pull the pin through the rivet and as this happens the rivet is deformed slightly so that it joins the metal or plastic pieces. This technique is used where the metal or plastic is thin and where the joint does not have to be very strong. It is ideal for joining aluminium or even thin sheets of plastic.

Riveting Rivets are used to join plates together. Before the use of welding, rivets were used in heavy industries such as ship building. ▫The steel plates used to build ships such as the Titanic were held together by steel rivets. Below are examples of cold rivets, these are the ones that are used in schools. Cold Rivets can be used to permanently join plates together. ▫Steel rivets are used for joining steel plates ▫Aluminium rivets are used for aluminum plates. Rivets are available made from other materials such as copper and brass. The material of the rivet normally matches the material to be riveted together. SNAP HEADPAN HEADMUSHROOMCOUNTERSUNK