Patent ID: 7819940
Filing Date: 2010-10-26
Classification: C21C,Y02P

Abstract:
1. Method of production of stainless steel of ferritic AISI 4xx group of steels, particularly the AISI 430 group of steels, based on liquid pig iron and FeCr solids, wherein a liquid slag-free pig iron, after preliminary treatment in a blast furnace ( 1 ) and DDD-treatment, is heated, refined or alloyed, reduced in a ADD-converter and, finally, adaptation/adjustment of a treated molten steel in a casting ladle ( 5 ) is carried out, characterized in that the DDD-treatment of the pit iron is carried out at extremely low temperatures of about 1150° C., in AOD-converter ( after heating and subsequent deslagging, for refining of the molten metal, oxygen is blown onto the molten metal by the top blowing lance, and a mixture of oxygen and inert gas (argon or nitrogen) is blown into the molten metal through side nozzles, wherein a ratio between the oxygen and the inert gas, starting with an oxygen-rich mixture, varies during the blowing process, and a total quantity of oxygen is constantly divided during a blowing process between the top blowing lance and the side nozzles.