Chromium oxide reduction from slag by silicon and magnesium

Experimental and theoretical studies were performed in order to estimate the effect of the basicity of the slag as well as the amount of reducing agents on the reduction of chromium oxide from a slag in contact with molten steel at 1600°C. The aim of this work was to compare the efficiency of magnesium and silicon as reducing agents of Cr₂O₃. The slag system contained CaO, MgO, SiO₂, CaF₂ and Cr₂O ₃ together with Fe-alloys (Fe-Si or Fe-Si-Mg). The maximum Cr yield was about 81% with Fe-44%Si-9%Mg and 88% with Fe-75%Si. That means that the reducing effect of Mg was much better than that of Si. Some experiments were conducted to study the effect of initial Cr in steel on the chromium oxide reduction reaction. Three initial Cr contents were tested (0.15, 2 and 4 mass%). It was found that chrome was partially bound into stable spinel phase MgO-Cr₂O₃ in the final slag. Thermodynamic estimations were made to determine the effect of process temperature, slag basicity and the amount of reducing agents in the slag on the Cr recovery. The efficiency of Cr reducing agents increased in the order: Si, Al, Ca and Mg. The Cr yield increased with slag basicity and amount of reducing agents.