Iron ore is the basis for most steals, how is pure iron extracted?
Iron ore is heated in a furnace in a process known as smelting.
Name two primary processes of metal
Rolling and extrusion.
How does the rolling process work?
The metal is heated until it is malleable. It is then squeezed between two special rollers. If a flat sheet is required, the rollers are circular. For a required shape, the rollers are shaped into dies. Each roller or die is slightly smaller than the previous one so that each time the metal passes through a die, it is reduced closer to the desired profile.
How does extrusion work?
Extruding involves pushing heated material through a die with the use of a ram. The ram creates a large pressure behind the material and it is quickly forced out of the die. The metal coming through the die needs supporting and cooling so that it does not lose its shape. Extrusions tend to be long thin parts with a constant profile such as window frames.
Name five stock forms of metals
Flat strip, round tube, hexagonal, channel, sheet.
What are the properties of ferrous metals?
- Contain iron.
- Will corrode and less protected.
- Are attracted by a magnet.
- Are strong, rigid and cheap.
Describe cast iron?
- It is composed of iron + 3% carbon.
- It is used for car brake discs, vices and the machine parts and fireplaces.
- It is brittle, can’t be forged or bent, strong in compression.
- It melts at 1200°C.
Describe mild steel
- It is composed of iron + 0.15–0.25% carbon.
- It is used for car bodies, structural beams, nuts and bolts.
- It is malleable, tough, ductile, good in tension, corrodes easily.
- It melts at 1600°C.
Describe high carbon steel
- It is composed of iron + 0.7–1.5% carbon.
- It is used for hammers, chisels, screwdrivers, scribers.
- It is very hard, difficult to cut, not very malleable.
- It melts at 1800°C.
What are ferrous metals?
Metals obtained from iron ore, they contain iron.
What are non-ferrous metals?
Metals that do not contain iron.
What are the properties of non-ferrous metals?
- Do not contain iron.
- Are not attracted by a magnet.
Describe aluminium
- It is a pure metal.
- It is used for cans, foil and window frames.
- It is malleable, soft ductile, corrosion resistant and it difficult to join.
- It’s a melts at 600°C.
Describe zinc
- It is a pure metal. It is used for corrosion proof coating for mild steel and die casting alloys.
- It melts at 420°C.
Describe copper
- It is a pure metal.
- It is used for pipework, electrical wires and the central heating cylinders.
- It is malleable, has good heat and electrical properties and corrosion resistant.
- It melts at 1083°C.
Describe tin
- It is a pure metal.
- It is used for coating on the cans and allied with other materials for solder.
- It is ductile, has a low melting point, is extremely resistant to corrosion.
- It melts at 230°C.
What are alloys?
Metals that are made up of two or more metals and other elements. This is done to improve their properties.
What can alloying metals do?
- Lower the melting point.
- Alter thermal and electrical properties.
- Make a material harder for cutting purposes.
- Improve resistance to corrosion.
- Help metal to flow better into a cast.
Describe brass
- It is composed of 60% copper and 40% zinc.
- It is used for ornaments, plumbing fittings, furniture hardware.
- It is corrosion resistant, polishes very well and easily joined.
- It melts at 950-1000°C.
Describe stainless steel
- It is composed of carbon steel + 18% chromium, 8% nickel and 8% magnesium.
- It is used for kitchen utensils, sinks and surgical instruments.
- It is resistant to wear and tear, durable, tough and hard.
- It melts at 1400°C.
Describe high speed steel
- It is composed of medium carbon steel plus high content of tungsten, chromium and vanadium.
- It is used for drill bits and cutting tools.
- It is very hard, brittle but extremely durable.
- It melts at 1400°C.
Describe pewter
- It is composed of 80% tin and 20% lead.
- It is used for Jewelry, decorative work and tankards.
- It is malleable, easily cast and polishes well.
- It melts at 230°C.
What are the definitions for the properties of metals?
- Durability - ability to withstand general wear and tear.
- Electrical - how well a material conducts or insulates electrical current.
- Toughness - ability to withstand sudden impact without fracturing.
- Hardness - ability to withstand dents and abrasive wear.
- Malleability – how workable a metal is.
Name three elements that can be added to a metal and a benefit it offers
- Manganese – improves toughness and hardness.
- Tungsten – allows steel to be cut at high strength.
- Chromium – increases resistance to wear and tear, improves durability.
