Continuous steelmaking process and plant and slag composition for use therein

Abstract

A process for the manufacture of steel in which a charge material comprising direct reduced iron, and optionally containing steel scrap, is continuously charged into a stationary electric arc furnace. Inside the furnace, a bath of molten steel and a continuous slag layer are maintained, the steel bath preferably having a volume of approximately 7 to 13 tap volumes. Heat for melting the charge material is preferably provided by open arcs between the electrodes and the metal bath, with the slag layer preferably being superheated to about 40 to 150° C. above the bath temperature. In order to prevent excessive superheating, the slag preferably has a melting point substantially the same as, or greater than, the bath temperature, with the slag melting temperature being adjustable by varying the amount of MgO in the slag. The slag preferably has low basicity to reduce the rate of refractory erosion. The steelmaking process is preferably carried out in a steel manufacturing plant in which a direct reduction furnace is closely coupled to the electric arc furnace. Preferably, the direct reduction furnace is “stacked” above the electric arc furnace so that the direct reduced iron can be fed to the electric arc furnace by gravity through inclined conduits.

Dependencies are inferred from the claim text.