Pig iron is an intermediate product in steel production via the blast furnace process .
Pig iron consists mainly of iron and also has a carbon content of around 4 to 5%, up to 3% silicon and up to 6% manganese , as well as small amounts of sulfur and phosphorus . These accompanying elements make pig iron very brittle when cold, so it is neither malleable (rollable) nor weldable.
In the past, pig iron was also called rough iron or rough iron.
Cast iron can have a gray or white fracture surface. If the silicon content predominates, gray cast iron with a gray fracture surface results after cooling . If, on the other hand, the manganese content predominates, the carbon combines with the iron to form iron carbide during cooling . The result is a radiant, white fracture surface (white pig iron). After solidification, the product is also used as a malleable cast iron, from which malleable cast iron is produced through a heat treatment (tempering) .
Pig iron cannot be forged or rolled. It must therefore be melted again or processed into finished products directly during casting . After the first cooling, it is too brittle for further processing .
White pig iron, on the other hand, is processed into steel in the converter process.
There, the excess carbon and other foreign substances are partially / completely removed from the pig iron in various ways (blowing in oxygen, electrochemical conversion).
Pig iron is poured into refractory lined ladle furnaces or torpedo wagons when tapping the blast furnace . After it has been transported to the steelworks, the excess carbon is burned in the converter by blowing in oxygen, and the pig iron is converted into steel. The heating caused by the incineration is compensated by adding scrap . The resulting steel is then converted from its still liquid state into the solid phase by continuous casting or ingot casting . If the silicon content is high, the carbon in the pig iron is deposited as graphite when it cools. The fracture surface then appears gray (gray pig iron).
States with the largest production
By far the most important producer country for pig iron is the People's Republic of China .
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- ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1509.
- ^ World Steel Association: Statistics Archive