Manganese and Chromium Distribution between CaO–SiO2–MgOsat.–CrO1.5–MnO Slags and Fe–Cr–Mn Stainless Steel

Abstract

The Mn and Cr equilibria between a Mn rich stainless steelmaking slag (CaO–SiO2–MgOsat.–MnO–CrO1.5) and Fe–Cr–Mn stainless steel were investigated in a temperature range from 1823 to 1873 K under Ar atmosphere. The partition ratios LMn and LCr between liquid slag and steel were determined as a function of slag composition and temperature. By combining the experimental results with thermodynamic calculations, it was found that, as basicity increases, LMn decreases, while LCr increases. The elevated basicity leads to a high MnO activity coefficient. On the other hand, the CrO1.5 activity coefficient decreases with higher slag basicities. The influence of MnO and CrO1.5 contents on the activity coefficients was also considered. It is concluded that in order to maximize Mn recovery during high Mn stainless steel production, a basic slag with a high MnO activity coefficient must be employed whereas high temperatures should be avoided.