SLAG METAL EQUILIBRIUM IN THE SMELTING OF HIGH-CARBON FERROCHROMIUM

The equilibrium between carbon-saturated Fe-Cr-Si-C alloys and SiO2-CaO-MgO-Al2O3-CrOx-FeOy slags was studied under atmospheres of argon and carbon monoxide at temperatures of 1500 and 1600-degrees-C. The equilibrium distribution of chromium, silicon, and iron between the slag and the metal phases was determined for different compositions of both phases under different atmospheres and temperatures. It is shown that silicon transfer from the slag to the metal increases with increasing temperature, decreasing carbon monoxide partial pressure, decreasing carbon content of the metal, increasing chromium-to-iron ratio of the metal, increasing silica content of the slag, and decreasing lime-to-alumina ratio of the slag. Some activity calculations were made for the experiments conducted at 1600-degrees-C in a carbon monoxide atmosphere. It is also shown that a decrease in the iron content and an increase in the slag basicity decrease the chromium content of the slag. A major proportion of the chromium present in the slag was found to be in the divalent state under the highly reducing conditions prevailing in the experiments. The chromous capacities of these slags were calculated and were found to decrease with increasing basicity.