Dissolution behavior of Al2O3 inclusions into CaO–MgO–SiO2–Al2O3–TiO2 system ladle slags

To investigate the dissolution behaviors of Al 2 O 3 inclusions in CaO–5wt%MgO–SiO 2 –30wt%Al 2 O 3 –TiO 2 system ladle slags, confocal scanning laser microscopy was conducted on the slags with different TiO 2 contents (0–10wt%), and scanning electron microscopy was performed to study the interfacial reaction between Al 2 O 3 and this slag system. The results disclose that the dissolution of Al 2 O 3 inclusions does not result in the formation of new phases at the boundary between the slag and the inclusions. In TiO 2 -bearing and TiO 2 -free ladle slags, there is no difference in the dissolution mechanism of Al 2 O 3 inclusions at steelmaking temperatures. Boundary layer diffusion is found as the controlling step of the dissolution of Al 2 O 3 , and the diffusion coefficient is in the range of 4.18 × 10 −10 to 2.18 × 10 −9 m 2 /s at 1450–1500°C. Compared with the solubility of Al 2 O 3 in the slags, slag viscosity and temperature play a more profound role in the dissolution of Al 2 O 3 inclusions. A lower viscosity and a lower melting point of the slags are beneficial for the dissolution. Suitable addition of TiO 2 (e.g., 5wt%) in ladle slags can enhance the dissolution of Al 2 O 3 inclusions because of the low viscosity and melting point of the slags, while excessive addition of TiO 2 (e.g., 10wt%) shows the opposite trend.