A steel mini mill is a facility which produces steel products from recycled scrap metal. Unlike integrated steel mills, which make new steel from iron ore in a blast furnace, mini mills melt and refine scrap steel using electric arc furnace (EAF) technology. According to a U.S. Environmental Protection Agency (EPA) report, while mini mills accounted for 10 percent of U.S. steel production in 1970, by 2006, over half of the national steel output was produced in mini mills.
The mini mill steel production process has several stages. Ferrous scrap is refined and melted in the EAF, after which the molten steel is often further refined in a ladle metallurgy process. The steel is then shaped into semi-finished products such as billets, blooms or slabs. These semi-finished products may be further processed into finished products using methods such as annealing, hot forming, cold rolling, pickling, galvanizing, coating, or painting. (See Reference 1)
Most of the steel produced in mini mills is carbon steel (as opposed to stainless or specialty steel) which is used in various applications including construction, automobile manufacturing, and in the production of appliances and other consumer products. Finished steel products produced in mini mills include rebar, wire rod, structural shapes, steel plate and sheet steel.
Mini mills are easier to start and stop than traditional integrated mills and can produce steel products in smaller batches than integrated mills. Mini mills are also more energy-efficient than integrated mills as they use mostly recycled inputs and require less electricity to operate. According to the Steel Manufacturer's Association, mini mill steel production results in a 65 percent to 90 percent reduction in greenhouse gas production when compared to steel production from iron ore.