Improvements relating to the production of steel castings of low sulphur content

摘要

A method of making steel castings having a sulphur content of less than 0.005%, comprising treating molten pig iron in a ladle with a limebearing desulphurizing agent and a stream of nitrogen, thereby lowering the sulphur content of the molten pig iron to less than 0.005%; converting said pig iron into steel in a furnace using sulphur-free fuel; teeming said steel into ingots and mechanically working the said ingots and thus obtaining scrap steel of low sulphur content; forming in an electric furnace a charge of steel containing sufficient of said scrap steel to maintain the sulphur content therein below 0.005%; and teeming said electric furnace charge into steel castings. The conversion process from pig-iron into steel may be carried out in a Bessemer or L/D converter. Part of the electric furnace charge may comprise an increment of the desulphurized pig-iron, a tolerated amount of other low sulphur content pig iron, or hot molten metal from the converting operation. Examples are given of the composition of the metal at each stage of the process. Specification 906,127 is referred to.