In this study, different trials using tracers were performed to investigate the source of slag inclusions in SPHC steel grade. Among Macro-inclusions by electrolysis in different trials, a large amount of Ba , which was added in LF refining slag, has been detected in macro-inclusions of LF refining, while little of that was found in tundish and continuous casting slab. It demonstrated that slag-entrainment occurred in LF refining but subsequent flotation removal reduced the effect of that significantly; The tracer element Sr for tundish powder and La for tundish linings were rarely detected. The ratios of defects containing Na, Sr, Ba and La in all the defects were 58.33%, 25%, 12.5% and 12.5% respectively which indicated that the mould flux contributed significantly to the generation of the slag inclusions, and the tundish flux and deoxidization product probably were the secondary source.
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