Steel is an iron-based alloy containing Carbon, Silicon, and Manganese, etc with typically a few tenths of a percent of carbon to improve its strength and fracture resistance compared to Iron.
Steel is manufactured in industrial plants known as Steel Mill. Steelmaking is the process of selective oxidation of impurities present in the charge material (Hot metal/Scrap/DRI) in the presence of suitable fluxes in the Steel Melting Shops (SMS).
It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-finished casting products are made from molten pig iron or from scrap.
Steel plants may be classified into two broad categories.
- Integrated Steel Plants (ISPs) follow the Blast Furnace–BOF route of steelmaking. An integrated steel mill has all the functions for primary steel production. The principal raw materials for an integrated mill are iron ore, limestone, and coal (or coke).
They are relatively large in size with individual module capacities ranging from 1 to 5 Mt of steel per year. A typical 3 Mtpa ISP would cover an area of 4–8 square km, i.e. a fairly large area, since a series of processes is involved.
- Mini Steel Plants (MSPs) use EAFs for steelmaking. Usually, it obtains most of its iron from scrap steel, recycled from used automobiles and equipment, or byproducts of manufacturing. Direct reduced iron (DRI) is sometimes used with scrap, to help maintain desired chemistry of the steel, though usually, DRI is too expensive to use as the primary raw steelmaking material.
A typical mini-mill will have an electric arc furnace for scrap melting, a ladle furnace or vacuum furnace for precision control of chemistry, a strip or billet continuous caster for converting molten steel to solid form, a reheat furnace, and a rolling mill.
MSPs are smaller in size with module capacities generally between 0.5 Mt and 1 Mt per year, and in some cases up to 2 Mt per year. A typical 1 Mtpa MSP would cover an area up to 2 square km to house EAFs and DRI producing facilities.