Ferrous and Non-Ferrous Metals
Ferrous metals contain iron, this means they corrode easily. They need to be protected by paint, or oil. They are magnetic.
Mild steel – Very malleable, rusts easily. Uses: Nuts, bolts and car bodies.
Cast iron – Melted down to pour into mould, it’s brittle but very strong. Uses: man holes, brake disks.
Stainless steel – Mouldable and resistance to wear. Uses: Kitchen sinks, cutlery, surgical instruments.
Non-ferrous metals contain no iron, they don’t rust when exposed to moisture and are not magnetic.
Aluminium – Light grey in colour and lightweight. Uses: Foil, ladders, sweet wrappers.
Copper – Orange in colour is soft and conducts heat and electricity well. Uses: Plumbing pipes and electrical wire.
Tin – Soft, easy to mould and anti-corrosive. Uses: Food packaging and storage cans.
Alloys are mixtures of two or more metals to achieve specific properties.
Brass – a mixture of brass and zinc. Uses: Decorative metal work like candle sticks and door handles.
Pewter – tin, antimony and copper are mixed to create a material which melts at low temperature to cast. Uses: Jewellery, cutlery, decorative frames.
Metal generally comes in sheets or ingots. Sheet metal can be cut and formed whereas ingots of metal are melted and cast into moulds.
Forming sheet metal
Cutting sheet metal can be done by hand with shears although it’s quite difficult, In industry it would be cut with compressed air shears, bench mounted lever shears or with a CNC plasma cutter. After cutting it can be bent using different shaped bending tools. Sheet metal can also be pressed between two shapes in a hydraulic press, car parts and kitchen sinks are made this way.
Iron and steel can be forged by hand, they have to be heated to a high temperature and hammered to form particular shapes. Forging is a very old and traditional way of shaping metal. Blacksmiths are able to make things like gates, swords and horseshoes.
Drop forging is a more industrial way of shaping molten metal, it is forced between two shapes with a single blow.
Moulds are created with oiled sand with an entrance in called a runner and an exit out called a riser. Liquid metal is poured into the runner until it is visible through the riser, it’s then cooled and the casting removed. The runner and riser are then trimmed off. The mould can only be used once.
A water cooled mould is created to have molten metal injected into it and then cooled. The mould can be used repeatedly.