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

Abstract

To investigate the dissolution behaviors of Al₂O₃ inclusions in CaO–5wt%MgO–SiO₂–30wt%Al₂O₃–TiO₂ system ladle slags, confocal scanning laser microscopy was conducted on the slags with different TiO₂ contents (0–10wt%), and scanning electron microscopy was performed to study the interfacial reaction between Al₂O₃ and this slag system. The results disclose that the dissolution of Al₂O₃ inclusions does not result in the formation of new phases at the boundary between the slag and the inclusions. In TiO₂-bearing and TiO₂-free ladle slags, there is no difference in the dissolution mechanism of Al₂O₃ inclusions at steelmaking temperatures. Boundary layer diffusion is found as the controlling step of the dissolution of Al₂O₃, and the diffusion coefficient is in the range of 4.18 × 10⁻¹⁰ to 2.18 × 10⁻⁹ m²/s at 1450–1500°C. Compared with the solubility of Al₂O₃ in the slags, slag viscosity and temperature play a more profound role in the dissolution of Al₂O₃ inclusions. A lower viscosity and a lower melting point of the slags are beneficial for the dissolution. Suitable addition of TiO₂ (e.g., 5wt%) in ladle slags can enhance the dissolution of Al₂O₃ inclusions because of the low viscosity and melting point of the slags, while excessive addition of TiO₂ (e.g., 10wt%) shows the opposite trend.

Keywords

inclusions / dissolution / ladle refining slag / titanium dioxide / confocal scanning laser microscopy

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