Iron (Fe)
For all it short comings, iron is the most used and cheapest metal. It
started its dominance of technology around 1000 BC, ending the mighty Bronze
Age and has maintained that dominance ever since.
By all accounts, iron should be the metal of last choice for most applications:
- it is dense and heavy
- it corrodes, rusting quickly in air and water
- it is very rare as natural metal and difficult to extract form its
ore
Why
use iron?
|
There is plenty of iron which can be found in an ore state and makes
up 5% of the Earth's crust and is second in abundance only to aluminium.
Australia has great mountains of iron ore, such as Mt. Tom Price and
Mt Newman in Western Australia. |
|
Abundance of iron
Iron
is the chief constituent of the Earth's core and is the most abundant
element in the Earth, making up 35% by mass. It is also found in the Sun
and other stars. The only free iron found naturally on Earth comes from
meteorites. Before man discovered how to extract iron from its ore, the
only iron available for use by man was that which fell to Earth as meteorites.
Iron was the original "star metal" and was much
prized for its hardness. One way of determining whether people have lived
in an area in the past is to look for meteorites: if you do not find any
there is a good chance that ancient man got to them first.
Metal iron is extracted by smelting the ore with carbon
(coke) and limestone. This is not an easy process and requires high temperatures.
The first iron was probably produced in a pottery kiln as the result of
heating red ochre glaze. See Production
of iron for more information.
The average human body contains about 4.5g of iron, mostly
in the form of haemoglobin in our blood.
Properties and uses
Pure iron itself is rarely used as it is too soft and prone to rusting.
Iron is more commonly alloyed with carbon to form steel which although
less malleable than iron, is stronger and less prone to rusting. Mixed
with other metals a whole range of steels can be produced: Stainless steel
which is highly resistant to corrosion through to mild steels, used to
make steel plate and cast iron. Cast iron is actually is a form of steel
which, although brittle is cheap to produce and can be cast easily.
Although iron reacts with water, acids and is heavy, hard
to produce and rusts quickly, iron is the most used metal. It all comes
down to money. It is cheap and we have a lot of it! The built-in redundancy
of iron also sells a lot more cars, bridges and train tracks. In fact,
protecting iron and steel against corrosion and replacing rusted structures
is a very big industry.
The future of iron
Iron will probably still dominate our building and transport technologies
in the foreseeable future, but the new space age materials such as aluminium,
plastics, ceramics, carbon composites and alloys will take over many of
the present uses of iron and steel. The future of iron is in new alloys
and combined with other materials to give strength and resistance to rusting.
|