Metals Design and Manufacture. Metals Produced by mining ore from the Earth Three main categories of metal: ▫Ferrous ▫Non ferrous ▫Alloys Available in.

MetalsDesign 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 metalsName Description Uses

Mild steel Ductile and malleable, rusts quickly when exposed

Nuts, bolts, car bodies, gates, girders

Cast iron Very strong in compression but brittle

Metal work vices, brake discs, manhole and drain covers

Tool steel Strong and very hard Hand tools – chisels, screwdrivers, hammers, saws

Stainless steel Resistant to wear and corrosion

Kitchen sinks, cutlery, dishes, teapots

High speed steel Brittle but resistant to wear Drill bits, lathe tools, milling cutters. Where high speeds and temperatures are created.

Non ferrous metalsName Description Colour Uses

Aluminium Light in weight Light grey in colour

Cooking foil, saucepans, cans, window frames

Copper Ductile and malleable. Excellent conductor of heat and electricity

Reddish-brown metal

Plumbing and electrical components.

Tin Ductile. Resistant to corrosion, malleable

Bright silver Coating on food cans and similar packaging

Zinc Weak metal, resistant to corrosion

Siver Coating on steel buckets, screws

Alloys Name Description Colour uses

Brass Hard metal, mixture of copper 65% and zinc 35%

Yellow Decorative metal work – door handles, candlesticks

Pewter Lead free alloy. Easily cast. Mainly tin and small amounts of antimony and copper

Bright mirror affect finish

Drinking tankards, jewellery, picture frames

Casting alloy Aluminium 3% and silicon 5%

Silver Engine components

Metal ProcessesDesign 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.

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