Steel is produced either by a blast furnace in an integrated steel facility or an electric arc furnace at a mini-mill.
An integrated steel mill uses blast furnaces to produce hot metal typically from iron ore, limestone and coke. Coke is a refined carbon product produced by fire coal in large coke ovens. Hot Metal is then converted through the basic oxygen process into liquid steel where it can be metallurgically refined. For Flat Rolled steel products, liquid steel is either teemed into ingots for later processing or cast into slabs in a continuous caster. The slabs are further shaped or rolled at a plate mill or hot strip mill. In the production of sheet products, the hot strip mill process may be followed by various finishing processes, including pickling, cold-rolling, annealing, tempering or coating process such as galvanizing. These various processes are often distinct steps undertaken at different times rather than during a continuous process and may take place in separate facilities. Steel produced by integrated mills tends to be cleaner and purer than steel produced by electric arc furnaces. These purer products are more often required for value added applications.
A mini-mill uses an EAF to melt steel scrap or scrap substitutes. For flat rolled products, liquid steel from the electric arc furnace is cast into slabs in a continuous casting process. The slabs are then rolled into finish product using the same process as integrated mills. Mini-mills generally produce a narrower range of products than integrated mills.