Tracer Research on Source of Inclusions in Steel From CAS-OB Refining and Continuous Casting Process

The sources of inclusions in steel during the CAS-OB refining and slab continuous casting process were investigated by means of tracer method.Results show that the micro-inclusions in steel both in the refining process and after calcium treatment include La which is the tracer in ladle slag.Micro-inclusions in steel from tundish include both La and Ce which is the tracer in tundish flux.Micro-inclusions in slab include part of La,Ce,K and Na.The reason is that the deoxidization products in molten steel react with the ladle slag,tundish flux and mould flux.The macro-inclusions in slab are mainly from the mould flux,and secondly from the ladle slag,and less from tundish flux.Macro-inclusions include trace elements of La,Ce,K and Na simultaneously.Macro-inclusions are composite inclusion of deoxidization products with the ladle slag,tundish flux and mould flux entangled into the molten steel.