Exploitation of slag obtd. from steel-making converters - where molten slag is mixed with fly ash and silica, and reduced in arc furnace to make casting powder

摘要

The slag obtd. during the refining of molten iron is mixed, pref. while molten, with fly ash from coal burning power stations; schist or coal shale; scrap contg. SiO2 and Al2O3; and/or molten blast furnace slag. Silica or sand is next added so the ratio Al2O3/SiO2 is max. 0.17; and the mixt. contains 30-70%, esp. 40-70% SiO2. The mixt. is kept molten via a burner, and is then reduced in an electric arc furnace with C reducing agents, followed by granulation in water, but recovering the reduced metals by decantation. Fluxes may be added to the mixt., e.g. CaF2, alkalies, Li2O and/or B2O3. The granulate is pref. milled to below 50 microns size. The milled prod. is employed as a casting powder, or as a constituent of such powder, used on the molten metal in the mould of a continuous casting plant.