metals design and manufacture. metals produced by mining ore from the earth three main categories of...
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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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