The distribution of manganese and sulfur between CaO_sat-SiO₂-Fe_tO-MgO_sat slags and molten iron

In the present study, the equilibria of manganese and sulfur between CaO_sat-SiO₂-Fe_tO-MgO_sat and molten iron were studied in the temperature range of 1,550 to 1,650°C. The decrease of CaO solubility by the addition of MnO was compensated by increasing MgO solubility. The addition of MgO to CaO_sat-SiO₂-Fe_tO slag slightly increased the activity coefficients of Fe_tO and MnO, and the properties of SiO₂ as an acidic oxide were clarified in this slag system. The oxygen content of metal in equilibrium with (37.5 to 41.1 mass percent) CaO-(5.5 to 6.6 mass percent) SiO₂-(41.6 to 43.7 mass percent) Fe_tO-(5.9 to 8.3 mass percent) MgO slags doubly saturated with CaO and MgO is expressed by the following equation: log[mass%O]=-5680/T + 1.87 The addition of MgO to CaO_sat-SiO₂-Fe_tO slag also increased the sulfide capacity of the slag. The approximate validity of the regular solution model was examined to formulate the thermodynamic properties of complex slags containing MnO.