Thermodynamic behavior and morphology of impurities in metallurgical grade silicon in process of O2 blowing

Gas blowing is a valid method to remove the impurities from metallurgical grade silicon (MG-Si) melt. The thermodynamic behavior of impurities Fe, Al, Ca, Ti, Cu, C, B and P in MG-Si was studied in the process of O2 blowing. The removal efficiencies of impurities in MG-Si were investigated using O2 blowing in ladle. It is found that the removal efficiencies are higher than 90% for Ca and Al and nearly 50% for B and Ti. The morphology of inclusions was analyzed and the phases Al3Ni, NiSi2 and Al3Ni were confirmed in MG-Si by X-ray diffraction. It was found that SiB4 exists in Si-B binary system. The chemical composition of inclusions in MG-Si before and after refining was analyzed by SEM-EDS. It is found that the amount of white inclusion reduces for the removal of most Al and Ca in the forms of molten slag inclusion and the contents of Fe, Ni and Mn in inclusion increase for their inertia in silicon melt with O2 blowing.