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.