GB631235A - Improvements in or relating to the manufacture of steel - Google Patents

Abstract

In a process for the production of steels and alloy steels having a low sulphur content (0.015 per cent or less), the first slag is removed silicon is added to the metal in sufficient quantity so that, after reaction, the required amount remains in the steel, and the steel which may contain a small proportion of iron oxide is intermixed with a basic slag composed of lime, alumina, and silica to produce a final slag having less than 1 per cent of iron oxide and falling within the area on the lime-silica-alumina diagram defined by the points CaO = 60% - Si O2 = 40% : CaO = 41% - Si O2 = 22% - Al2 O3 = 37% : CaO = 45% - Al2 O3 = 55% and the point CaO = 100%, the steel having a final silicon content higher than 0.05 per cent and generally 0.2 to 0.4 per cent. The silicon added, which may amount to 1 per cent of the bath weight may be replaced in part by Al, Cu, or Mg, and lime and silica in the basic slag partly replaced by magnesia, baryta, strontia or soda and by alumina, titanium oxide or zirconium oxide respectively. The basic slag may contain up to 5 per cent of iron and/or manganese oxide and when the silica content is more than 20 per cent the lime should have less than 0.1 per cent of sulphur. Specification 533,671 is referred to.