Effect of TiO2 addition on the dissolution of MgO·Al2O3 inclusions in TiO2-bearing ladle slags

Abstract

In order to clarify the removal behaviors of inclusions, the dissolution of MgO·Al₂O₃ inclusions in CaO–SiO₂–MgO–Al₂O₃–(0–10%)TiO₂ slags was observed in situ at 1450°C–1500°C by confocal scanning laser microscopy (CSLM), and the slag-inclusion interfacial reaction was investigated by the scanning electron microscope (SEM). It was found that the addition of TiO₂ in the slags may change the dissolution mechanism of MgO·Al₂O₃ inclusions, and the dissolution was controlled by diffusion in the boundary layer or in slag with a diffusion coefficient ranging from 2.38 × 10⁻⁹ to 7.35 × 10⁻⁹ m²·s⁻¹. Besides, the addition of TiO₂ slightly changed the solubility of MgO·Al₂O₃ in the slags, but its impact on slag properties played a more profound role in the dissolution of the inclusions. An appropriate addition of TiO₂ (e.g., 5%) helped the dissolution due to the lower viscosity and melting point of the slag, while an excessive TiO₂ content (e.g., 10%) showed an opposite effect. The dissolution rates of MgO·Al₂O₃ inclusions were smaller than that of Al₂O₃ inclusions. The lower chemical driving force of MgO·Al₂O₃ and the precipitated MgO particles near the inclusion-slag boundary were the main reasons to result in the lower mass transfer rates.