Effect of FeO content in Slag on formation of MgO•Al2O3 inclusion for Al-killed steel

In this study, experiments are carried out to investigate the effects of FeO content in slag on formation of MgO center dot Al2O3 inclusion for Al-killed steel, and thermodynamic and kinetics analysis are made to explain the experimental phenomena. Result shows that the dissolved [Mg] in steel is supplied from the reduction of MgO in slag by [Al] in steel after deoxidation with Al. However, the specific [Mg] content in steel is affected largely by FeO content rather than MgO content in slag. At low FeO content, the dissolved [Mg] in steel in equilibrium with FeO in slag is enough to transform most of the Al2O3 into MgO center dot Al2O3 inclusions; at high FeO content, the dissolved [Mg] in steel can be expended by FeO in slag at the slag/metal interface and the formation of MgO center dot Al2O3 can be restrained. In present work, FeO content in slag should be controlled at about 5 wt-% to avoid the formation of MgO center dot Al2O3 as well as minimize the reoxidation between steel and slag as much as possible.