The Raw Materials Of Steel
Producing steel is a complex process and one that requires several raw materials in order to create the end result. What's more, those raw materials combine to create another raw material - one which is then used to produce steel, so it is a multi-levelled process.
This second raw material is called pig iron. It is composed of three other raw materials, which are processed iron ore, coke - which is comprised of around ninety per cent carbon and is the residue left following the heating of coal without any air present - and limestone. Pig iron is created in a continuous process: the three raw materials are added to the blast furnace at intervals rather than all at once at a single moment. During the process, the limestone acts as a purifier and forms a surface on top of the liquid metal inside the furnace. Its effect is in oxidising the liquid, which helps to remove the impurities.
It takes around two tonnes of iron ore, one tonne of coke and half a tonne of limestone to produce just one tonne of pig iron. Pig iron is very brittle, thanks to its iron content of around 3.5-4.5 per cent. It can be sold there and then in the steel trading industry or used by its producers to complete the steelmaking process. There are several options for what to do next.
To make wrought iron, the pig iron must be melted down, mixed with slag and then hammered down, which will eliminate most of the carbon. The end result will be malleable, strong wrought iron that has a variety of uses in construction. Cast iron can be created by melting the pig iron along with scrap iron before adding alloys whilst the impurities are being removed by the smelting process.
Steel, however, is produced when the pig iron refining process continues. As steel is simply iron with the majority of impurities removed from the material, a variety of processes can be employed to remove such impurities from the pig iron so the remaining result is steel. An open hearth can be employed to put the pig iron through the same process it previously underwent, using limestone to remove more impurities and thus creating steel. The Bessemer process also removes impurities, this time by using air to oxidise the material, with the oxides being burnt off by carbon monoxide. Most likely, however, steel will be created using a basic oxygen furnace as the process is a lot faster than the aforementioned.
The steelmaking process is a fascinating one where just three raw materials of steel can combine in a process that creates one of the world's most useful materials.
This second raw material is called pig iron. It is composed of three other raw materials, which are processed iron ore, coke - which is comprised of around ninety per cent carbon and is the residue left following the heating of coal without any air present - and limestone. Pig iron is created in a continuous process: the three raw materials are added to the blast furnace at intervals rather than all at once at a single moment. During the process, the limestone acts as a purifier and forms a surface on top of the liquid metal inside the furnace. Its effect is in oxidising the liquid, which helps to remove the impurities.
It takes around two tonnes of iron ore, one tonne of coke and half a tonne of limestone to produce just one tonne of pig iron. Pig iron is very brittle, thanks to its iron content of around 3.5-4.5 per cent. It can be sold there and then in the steel trading industry or used by its producers to complete the steelmaking process. There are several options for what to do next.
To make wrought iron, the pig iron must be melted down, mixed with slag and then hammered down, which will eliminate most of the carbon. The end result will be malleable, strong wrought iron that has a variety of uses in construction. Cast iron can be created by melting the pig iron along with scrap iron before adding alloys whilst the impurities are being removed by the smelting process.
Steel, however, is produced when the pig iron refining process continues. As steel is simply iron with the majority of impurities removed from the material, a variety of processes can be employed to remove such impurities from the pig iron so the remaining result is steel. An open hearth can be employed to put the pig iron through the same process it previously underwent, using limestone to remove more impurities and thus creating steel. The Bessemer process also removes impurities, this time by using air to oxidise the material, with the oxides being burnt off by carbon monoxide. Most likely, however, steel will be created using a basic oxygen furnace as the process is a lot faster than the aforementioned.
The steelmaking process is a fascinating one where just three raw materials of steel can combine in a process that creates one of the world's most useful materials.
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