Production of stainless steel

摘要

A process of producing stainless steel of not more than 0.03 per cent carbon content is characterized by melting in an electric furnace having carbon electrodes a charge consisting essentially of chrome ore disposed along the banks of the furnace only in such amount as to be assimilated in the melting operation, base steel scrap, stainless steel scrap and a material high in iron oxide all disposed in the middle of the furnace and on the chrome ore, thereby forming an iron and chromium rich bath and a supernatant slag including iron and chromium oxides and adding to the slag a silicon-containing reducing agent of low carbon content for recovering the metallic iron and chromium from their oxides. The base steel scrap may be disposed over the furnace bottom, the stainless steel scrap over the ore and the iron oxide-containing material over the base scrap. A further and preferably larger quantity of chrome ore is added during the melt-down of the initial charge. The reducing agent is preferably crushed ferrosilicon substantially relieved of fines and having a low carbon content, e.g. ferrosilicon between about 1 inch and 5 inch screen size. Additions of nickel, copper, tungsten, vanadium, aluminium, titanium, niobium, molybdenum, or zirconium may be made in the furnace or, after tapping the stainless steel, in the ladle. The production of a steel containing 0.029 per cent carbon, 18.02 per cent chromium, 11.68 per cent nickel, 0.62 per cent silicon, 0.8 per cent manganese, about 0.015 per cent each of sulphur and phosphorus and the remainder iron is described. Specifications 428,950 and 437,186 are referred to.