The removal of tramp elements from liquid iron by calcium

The removal of tramp elements such as tin, copper and lead from liquid iron has been studied in the present work. The removal of tin or copper from liquid iron containing 50 wt% tin or copper to a slag phase containing a mixture of calcium and calcium chloride has been carried out in capped alumina crucibles at 1175-1375$\sp\circ$C. The variables such as temperature, ratio of the initial mass of calcium to the initial mass of calcium chloride, and ratio of the initial mass of the slag to the initial mass of the metal have been studied. The tin content of the metal phase decreased from 50 wt% to 39.3 wt% and the copper content of the metal phase decreased from 50 wt% to 45.6 wt% at 1175$\sp\circ$C when the above ratios were both unity. The activity of calcium in the alumina-saturated Ca-CaCl$\sb2$ system was of the order of 10$\sp{-5}$ at 1175$\sp\circ$C. The activity coefficient of Ca$\sb2$Sn in alumina-saturated Ca-CaCl$\sb2$-Ca$\sb2$Sn-CaO slags was about 10 at 1175-1275$\sp\circ$C. The experiments were not feasible in alumina and magnesia crucibles at 1600$\sp\circ$C because of the leaking of the crucibles in presence of calcium. There was almost no removal of tin from Fe-2 wt% Sn alloys in the experiments carried out in graphite crucibles using calcium carbide at 1260$\sp\circ$C and 1600$\sp\circ$C. Lead was almost completely removed from liquid iron by evaporation in 5 hours without having to use any slag phase