THERMODYNAMICS OF MNO, FEO, AND PHOSPHORUS IN STEELMAKING SLAGS WITH HIGH MNO CONTENTS

The thermodynamics of manganese oxide and iron oxide and the phosphate capacity of CaO-SiO2-MnO-FetO-P2O5-MgOsat slags with high MnO content s relevant to the smelting of MnO ores in steelmaking were investigate d. Previous data were limited to about 5 pet MnO, whereas in this stud y MnO contents up to 25 pet were studied. The activity of MnO showed p ositive deviation from ideal behavior and increased with basicity, whi le that of FetO decreased with basicity. This is reflected in that the manganese distribution ratio at a given FetO content decreases with b asicity and high Mn in the metal is favored by high basicity. CaF2 add itions up to 4 pet did not affect the activities of MnO and FetO. The activity coefficient of P2O5 decreases and the phosphate capacity incr eases with basicity. There was not adverse effect of high MnO contents on the dephosphorizing abilities of the slags.