Manufacture of Steel
Impure iron from the blast furnace and even pure iron have limited uses.
Iron produced in the blast furnace contains carbon impurities which make it brittle and unsuitable for supporting large buildings for example.
The process for making steel is called the basic oxygen steel-making process or BOS process.
Oxygen gas is blown through the oxygen lance at high pressure, this reacts with impurities such as carbon and sulphur and oxidises them. These leave as gas (carbon dioxide and sulphur dioxide) and pure iron remains.
Calculated amounts of carbon or other metals are added to make a range of different alloys.
An alloy is a mixture of two or more elements (isially metals). They are usually stronger than the elements making them up.
Here are some steel alloys with a brief description and usage:
|Carbon Steel||The most common type of steel with 0.1 to 1% carbon depending on the strength. An important use of this steel is providing the skeleton of large buildings like bridges, airports and skyscrapers.|
|Stainless Steel||Contains about 18% chromium (Cr) and small amounts of nickel (Ni). It is used for making cutlery because it is resisitant to corrosion. It has also been used in alot of famous skyscraper exteriors.|
|Titanium Steel||Contains 0.5 - 2% titanium and various amounts of other metals it is very hard and used in aircraft and armour plating.|