Evolution of Inclusions in Fe-13Cr Treated by CaO-SiO2-Al2O3-Based Top Slag

Experiments were carried out to determine the effect of Al2O3 in the slag of the CaO-SiO2-Al2O3-MgO-CaF2 system on the cleanness of Fe-13Cr stainless steel deoxidized by ferrosilicon. Increasing the Al2O3 content in basicity = 2.28 slag can reduce the usage of CaF2 and benefit the obtainment of a good kinetic condition for inclusion removal, but over 21 pct would lead to a higher total oxygen content in the melt and make the inclusion composition more complex. It is found that increasing basicity in 16 pct Al2O3 slag would have a good deoxidation ability and accelerate the transformation from high Al2O3 inclusions to low melting point CaO-Al2O3-SiO2-MgO system inclusions, but basicity over 2.58 would lead to high content of [Al] in liquid steel, which would promote the formation of MgO-Al2O3 inclusions. Therefore, it is not suitable to add a high content of Al2O3 into high-basicity slag. Adding Al2O3 into slag of 2.28 in basicity until a content of 16 pct could achieve inclusion plastication within 45 minutes without Ca treatment, which has potential application in industrial production.