Optimized Decarburization Process for Stainless Steel with Combination of Refining in Converter and RH Degasser

摘要

A new combined decarburization process for the production of stainless steel has been established at No.1 Steelmaking Shop in Chiba Works of Kawasaki Steel Corp. The process utilizes K-BOP (top and bottom blowing converter) for decarburizing the stainless steel melt with an oxygen/inert gas mixture and KTB method during RH degassing (oxygen top blowing onto the molten steel in vacuum vessel) for efficient vacuum decarburization. By this process, it has become possible to produce high chromium stainless steel with ultra-low carbon and low nitrogen more easily and with higher productivity than the conventional K-BOP and VOD process. The carbon and nitrogen contents of the steel product obtained by the new process are low enough and equivalent to those by the K-BOP and VOD process. Another advantage of the KTB method is higher oxygen-utilizing efficiency for decarburization during RH degassing by the optimized operation of oxygen blowing for the production of a certain steel grade such as SUS 304 whose upper limit of nitrogen content is relatively high.