Steel Dynamics may operate mini-mills, but it produces big steel. Steel Dynamics, Inc. (SDI) operates electric arc furnace mini-mills, steel scrap processing and metals recycling centers, and steel fabrication facilities. SDI sells to companies in the automotive, construction, and manufacturing industries, as well as to steel processors and service centers, primarily in the Midwestern and Eastern US. Among its mini-mill output are beams, rails, and other products used in the construction, industrial machinery, and transportation industries.