Thermodynamic studies of MgO saturated EAF slag

Foamy slags are widely practiced in electric arc furnace (EAF) steel production, reducing energy consumption, improving yield, reducing furnace noise, and increasing refractory service life. Control of slag chemistry within a specific range is necessary to achieve maximum benefits from slag foaming. The 'optimum' slag during EAF steel production is MgO saturated, containing a suspension of magnesium wüstite (MgO.FeO) particles. A thermodynamic program, FACTSAGE, was utilised to study a simplified steel slag system containing four slag oxides (MgO–CaO–FeO–SiO2), to predict the dual saturation level of CaO and MgO phases and to predict the MgO slag saturation level with variations in oxygen partial pressure, temperature and slag basicity. Results from thermodynamic calculations indicate that there are linear relationships among slag oxides and slag basicity which can be used to predict and control slag chemistry for foaming. Model data were compared with experimental data and models developed by other researchers.