Mathematical Study of the Formation Mechanisms of Complex Oxide Inclusions in Si–Mn-Killed Steel

Deoxidation and inclusion control are important aspects of secondary steelmaking. Due to various reactions taking place between the solutes in the molten steel reactor, it sometimes becomes difficult to understand the formation mechanisms of complex oxide inclusions. In this study, a mathematical model including nucleation and mass transfer is proposed for the prediction of composition evolution of primary oxide inclusions generated after steel deoxidation by the addition of Si and Mn. Complex inclusions resulting from homogeneous nucleation and transformation of existing simple oxides like silica are taken into consideration. The results show that the spontaneous nucleation of complex oxides is favorable and has almost three times higher driving force relative to simple oxides during deoxidation of steel. Also, the transformation of simple to complex oxides is essentially very fast (< 1 second) owing to the high driving forces for mass transfer. These results demonstrate the model’s ability to predict the chemical composition of the complex oxide nuclei growing in the steel melt along with the final inclusion composition.