Iron is hard, brittle, fairly fusible, and is used to
produce other alloys, including steel. The following table provides all
the features of iron as a material.
Iron is a metal extracted from iron ore using blast
furnace, and is almost never found in the free elemental state.
The Blast Furnace
|
Cast iron
The molten iron from the bottom of the furnace can be used as
cast iron.
Cast iron is very runny when it is molten and doesn't shrink
much when it solidifies. It is therefore ideal for making
castings - hence its name. However, it is very impure,
containing about 4% of carbon. This carbon makes it very hard,
but also very brittle. If you hit it hard, it tends to shatter
rather than bend or dent.
Cast iron is used for things like manhole covers, guttering and
drainpipes, cylinder blocks in car engines, Aga-type cookers,
and very expensive and very heavy cookware. |
|
Cast iron has already been mentioned above. This section deals with the
types of iron and steel which are produced as a result of the
steel-making process.
If all the carbon is removed from the iron to give high purity iron, it
is known as wrought iron. Wrought iron is quite soft and easily worked
and has little structural strength. It was once used to make decorative
gates and railings, but these days mild steel is normally used instead.
Steel, manganese steel, stainless steel and titanium steel are the most
popular and widely used alloys of iron.
Steel is a mixture of iron and carbon. The amount of carbon may range
from 0·1% to 1·5% giving steels of different properties. The
exact composition of the steel can be monitored by atomic emission
spectroscopy during production.
Low carbon steel (less than 0·25% carbon) is called mild steel.
Mild steel is cheap, strong and easily shaped. It is the main metal for
construction and is used to make bridges, buildings, ships and vehicles.
| |
Iron mixed withtext |
Special properties |
Uses include |
| Stainless steel |
Chromium and nickel |
Resists corrosion |
Cutlery, cooking utensils, kitchen sinks,
industrial equipment for food and drink processing |
| Titanium steel |
Titanium |
Withstands high temperatures |
Gas turbines, spacecraft |
| Manganese steel |
Manganese |
Very hard |
Rock-breaking machinery, some railway track (e.g.
points), military helmets |
High carbon steel (more than 0·5% carbon) is stronger than mild
steel but it is more brittle. High carbon steel is used to make tools
and cutters.
Steel has the disadvantage of needing a protective coating (for example
paint) or it will react with oxygen in the air and rust. Rusting is the
reverse of the process in the blast furnace - see rusting.
Manganese steel is an alloy of iron (84%), manganese
(15%) and carbon (1%). Manganese steel is extremely hard and is used for
railway points and dredging equipment.
Stainless steel is an alloy of iron (80%), chromium
(15%), nickel (4%) and carbon (0·5 to 1%). Stainless steel is
strong and hard, with a very high resistance to corrosion (due to
chromium). It is used for cookware, cutlery and industrial chemical
plant.
Titanium steel alloy may contain 0·5 to 2%
titanium with varying amounts of other metals including chromium, nickel
and vanadium. Titanium steel is very hard and finds uses in aircraft and
armour plating.
Iron
Alloy Casting