Effect of CaO–SiO2–Al2O3–MgO top slag on solute elements and non-metallic inclusions in Fe-xMn(x = 10, 20 mass pct) steel

Abstract

Medium/high manganese steels have broad application prospects in automotive industry, cryogenic material, etc. because of excellent properties. Precise control on steel composition and improvement of cleanliness are very important for commercial production of these steel grades. In this study, the effect of CaO–SiO2–Al2O3–MgO slag on solute elements and inclusions of Fe-xMn(x = 10, 20 mass pct) steel was studied and discussed. After slag/steel reaction, the concentration of Mn and S in steel reduced, while Si increased. Most MnO type inclusions, which were the main inclusions in master high manganese steel, transformed to MnO–SiO2 type and MnO–Al2O3–MgO type, with MnO–SiO2 sharing the majority. Thermodynamic analysis indicates that the change of solute elements and inclusions was mainly the result of reaction SiO2(s) + 2[Mn] = 2MnO(s) + [Si] between molten steel and top slag as well as slag desulphurization. Increase of oxygen potential of the reaction system would restrain the reaction. Because of the inclusion absorption by top slag, large sized inclusions decreased and steel cleanliness improved greatly after CaO–SiO2–Al2O3–MgO slag was added.