Optimal Alkalinity Model of Ladle Furnace Slag for Bearing Steel Production Based on Ion–Molecule Coexistence Theory

Abstract

The fatigue life of bearing steel is closely related to the total oxygen content (T(O)) of the liquid steel. In order to stably and effectively control the T(O) during the ladle furnace (LF) refining process, we established a calculation model of optimal alkalinity for the refining slag CaO–SiO2–Al2O3–MgO–FeO–CaF2 at 1853 K based on ion–molecule coexistence theory (IMCT). Here, the influencing factors are discussed. The results show that the maximum value of NFeO occurred when the optimal alkalinity was around five at varied FeO contents, and that the optimal alkalinity basically remained the same with changes in FeO content. With the increase of MgO content, the optimal alkalinity decreased. However, the change in the value of NFeO against the higher alkalinity was not obvious at a given MgO content. The effect of Al2O3 content on the optimal alkalinity was opposite to that of MgO. With the increasing Al2O3 content, the optimal alkalinity obviously increased, while the maximum value of NFeO occurred when the Al2O3 content varied from 35 wt% to 45 wt% at higher alkalinity. The higher w(CaO)/w(Al2O3) mass ratio had a distinct effect on the value of NFeO against alkalinity, while the effect of alkalinity on the value of NFeO was not obvious at a fixed CaF2 level. This optimal alkalinity model based on IMCT can provide a certain guiding role in the process of refining slag composition optimization and is conducive to effectively controlling total oxygen content in the refining process.