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The basis of slag is limestone used as auxiliary material in the production of iron and steel. |
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While limestone may seem unrelated to the production of iron and steel, it actually is an essential auxiliary material that is added during the production process.
During the process of reducing iron ore, it is necessary to remove the silica, alumina (Al2O3), and other non-ferrous components contained in iron ore.
The added limestone fuses with these components and lowers their melting point, making it easier to separate them from the iron and recover them. This recovered substance is slag.
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Process that generates iron and steel slag |
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Iron and steel slag can be broadly classified into blast furnace slag that is generated when iron ore is melted and reduced in a blast furnace, and steelmaking slag that is generated during the steelmaking processes used to modify the components of iron.
Blast furnace slag is a combination of silica and other non-ferrous components of iron ore, ash from coke used as a reducing material, and limestone auxiliary material. Because its specific gravity is less than that of pig iron, during the heating process the molten slag rises above the pig iron allowing it to be easily separated and recovered.
Steelmaking slag is generated by the process that turns pig iron produced by a blast furnace into tough and highly workable steel. Converter slag is the oxidized material that is generated when lime and other auxiliary materials are added and oxygen is blown onto the pig iron in order to remove carbon, phosphorous, sulfur, and other components from the pig iron and refine it to produce strong steel. The other type of steelmaking slag, electric arc furnace slag, is generated when iron scrap is melted and refined.
Iron and steel slag products and production process |
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