GB382754A - Processes of making nickel steels - Google Patents

Abstract

Steel containing nickel particularly stainless steel is made by introducing into a steel bath molten nickel which has been produced by heating nickel matte with silicon or a silicon alloy in the presence of a basic slag. The reduction of the matte may take place in the presence of the steel bath and the reducing agent which should be substantially carbon free may be commercial silicon, ferrosilicon, or a silicon alloy containing a metal to be alloyed with the steel, for example nickel or chromium. If nickel-silicon, or ferro-nickel-silicon is used to reduce the matte both matte and reducing agent will contribute nickel to the steel. In making stainless steel, chrome ore, nickel matte, and reducing agent, in admixture together, or in two separate batches, of reducing agent with chrome ore and nickel matte respectively, are charged with lime and if desired fluorspar and other fluxes into an open arc electric furnace. A low carbon steel bath may be placed in the furnace before starting the smelting either by melting steel scrap and decarbonizing or by supplying the furnace with molten metal from a Bessemer or open-hearth furnace. Alternatively steel scrap may be incorporated in the smelting charge or supplied to the furnace after the smelting is completed. In an example an 18 : 8 chromium nickel stainless steel is produced by melting steel and decarbonizing by an oxidizing slag to 0,02 per cent of carbon, charging a batch comprising chrome ore, ferrosilicon, and lime followed by another batch comprising nickel matte, ferrosilicon, and lime. The slag is removed and low carbon ferromanganese is added to the steel in the furnace after which a finishing slag comprising lime and quartzite is formed. The steel is worked under the slag to which small additions of ferrosilicon are made until metal and slag are deoxidized, and is then tapped into a ladle, treated with 0,25 per cent of silicon as 50 per cent ferrosilicon and cast. Reducing agents containing silicon with nickel, or chromium or both nickel and chromium may be prepared by reducing nickel matte, or chromite, or both nickel matte and chromite simultaneously with silicon by means of carbon in the electric furnace.