Development of New Refining Process for Manufacture of Stainless Steel

A new refining process for manufacture of stainless steel has been developed using 20t AOD furnace in Shibukawa Plant, Daido Steel Co., Ltd. since 1989. This process, named VCR (Vacuum Converter Refiner) process, consists of AOD furnace and vacuum system. Under vacuum condition in AOD process, we can more effectively refine the molten steel at the final stage of decarburization and the stage of reduction. The characteristics of this new process are as follows. (1) Decarburization rate constant at low carbon range is about 2 times larger than that of conventional AOD process. (2) Ultra low carbon stainless steel grade is made more easily and quickly than VOD process. (3) It is possible to reduce the consumpution of argon gas for refining and ferrosilicon for reduction. This VCR process was applied to 70t AOD furnace which was installed in Chita Plant, Daido Steel Co., Ltd. in November 1991. The outline of VCR process is described and some operational results obtained at 20t and 70t AOD furnaces are given.