Effect of Al 2 O 3 content on metallurgical characteristics of refining slag

The metallurgical effects of Al2O3 in CaO–Al2O3–SiO2–MgO system slag on the desulfurisation ability, inclusions and steel cleanliness were investigated using thermodynamic calculations, laboratory experiments and industrial tests. The results indicate that: with a decreasing Al2O3 content in top slag and with the slag basicity remaining constant, the calculated aCaO (activity of CaO), Cs (sulphide capacity) and of the slag increase; the measured total oxygen content decreases, inclusion number and area decrease, and the average content ratio, of inclusions increases. Compared with the steel refined using conventional desulfurisation slag N2 (B (basicity): 7.0, Al2O3:30%), the steel refined using slag N1 (B: 4.5, Al2O3:20%) gives a lower sulphur content, and the inclusions contain more MgO and less Al2O3 and contain a certain amount of SiO2. The Al2O3 content has a great effect on the metallurgical characteristics of the refining slag.