Effect of TiO₂ Addition on the Viscosity of Ladle Refining Slags

In order to understand the effect of TiO₂ on the viscosity of ladle refining slags, the viscosity of CaO-SiO₂-30pct Al₂O₃-5pct MgO-TiO₂ refining slag system was measured in laboratory, and the activation energy of the viscous flow was calculated. FTIR and Raman were also used to analyze the change of slag structures. The results show that with the increase of TiO₂ content (0 to 10 pct) in the slag system, the viscosity of the slags decreases first and then increases. A low TiO₂ content (e.g., 2 pct) in the ladle slags can weaken the strength of the slag structure due to the formation of [TiO₄]⁴⁻; while sufficient TiO₂ (e.g., 10 pct) will lead to the formation of [Ti₂O₆]⁴⁻, and further increase the degree of polymerization (DOP) of the slags. Although silicate structure can be depolymerized by TiO₂, the [AlO₄]⁵⁻-tetrahedron structure variation plays more profound role in the change of viscosity. With the increase of the basicity (w(CaO)/w(SiO₂) = 2 to 10) of the TiO₂-containing slags, the viscosity decreases. The free oxygen provided by CaO decreases the DOP of both aluminate and silicate structures. The proper addition of TiO₂ into ladle refining slags is very possible for the refining of Ti-bearing steel grades due to the positive effect on the melting point and viscosity of the slags.