Features of Nonmetallic Inclusion Formation and Evolution During Ladle Treatment and Continuous Casting of Special Alloy Steels

Resumo

Features of nonmetallic inclusion formation and evolution in special alloy steels during ladle treatment and continuous casting are studied for special alloy steel 40Kh. The main differences in types, sizes, and morphology of nonmetallic inclusions in relation to steel deoxidation scheme are analyzed. It is established that the composition of more than 97% of oxide inclusions present belongs to CaO–Al₂O₃–SiO₂, Al₂O₃–MgO–SiO₂, CaO–Al₂O₃–MgO, CaO–Al₂O₃–MgO~5% SiO₂, Al₂O₃–MnO–SiO₂ systems. The main factors that affect the formation of aluminum-magnesium spinel are determined. It is shown that a non-optimal slag regime in a tundish leads to formation of silicate inclusions with cross section of more than 1000 μm², even with a steel aluminum content more than 0.015 wt.%.