关键词: SPA-H钢, 夹杂物, LF精炼, CAS精炼, 洁净度

Abstract: To reduce the cost, one steel mill try to use CAS refining to replace traditional LF refining process in SPA-H steel. However, it is still in dispute whether this replacement may worsen the cleanliness of steel coils. The total oxygen content and automatic feature analysis (AFA) in ASPEX SEM were used to evaluate the cleanliness of SPA-H steels coils, and the effect of refining methods，such as CAS refining and LF refining process on them were compared. The result shows that the T.O mass fraction of coils were almost the same, ranging from 18×10^-6 to 19×10^-6, Four different kinds of micro inclusions were detected in steel coils: CaS-Al₂O₃，Al₂O₃,(Ca,Mn)S and TiN, and all the macro inclusions were pure MnS. Furthermore, (Ca,Mn)S and Al₂O₃ inclusions account for over 90 % of inclusions in CAS refining process while CaS-Al₂O₃dominates micro inclusions in steels coils for LF refining process, occupying 81.3 %.The number density of largesized inclusions for CAS refining process were much larger than that for LF refining process. Equilibrium inclusion composition calculated by Factsage agree well with the experimental results. Lower calcium yield ratio and smaller Ca/S ratio for CAS refining process due to the relatively higher TFe content in refining slag may account for the difference of the inclusions between the two different refining methods. Accordingly, Ca alloy should be more added and top slag should be reduced when refining SPA-H steels using CAS process.