Effect of TiO2 on Viscosity and Structure of Low-Fluoride CaF2-CaO-Al2O3-MgO-Li2O Slag for Electroslag Remelting

The effect of TiO2 on viscosity of low-fluoride CaF2-CaO-Al2O3-MgO-Li2O slag for electroslag remelting was investigated under continuous cooling conditions and the Fourier transform infrared (FTIR) and the Raman spectroscopy were employed to analyze the correction between the quenched slags and corresponding structure. Results show that the slag viscosity decreases with increasing the TiO2 content. At the TiO2 content up to 13.1wt%, the corresponding viscosity values slowly decrease from 0.067, 0.059, 0.056 Pa•s to 0.054 Pa•s as the temperature increases from 1743, 1793, 1843 K to 1893 K and at higher temperature of 1843 K or above, TiO2 addition has a relatively small effect on lowering the slag viscosity. The calculated activation energy of viscous flow decreases from 58.0, 47.7, 42.8 kJ/mol to 38.6 kJ/mol with increasing the TiO2 content from 0 wt%, 4.3 wt%, 8.7 wt% to 13.1 wt%. Additionally, the FTIR results reveal that with the addition of TiO2, [AlOnF4-n]-tetrahedral complexes and [AlO4]-tetrahedral network structures depolymerize, but [AlO6]-octahedron is not found in the slag. Simultaneously, it can be seen from the Raman spectra that with the addition of TiO2, the depolymerization of the Al-O-Al linkage occurs in the [AlO4]-tetrahedral network structures, the part Q4 units transform to Q2 units and the O-Ti-O and Ti-O-Ti chains form. These results suggest that polymerization degree of these slags decreases with increasing the TiO2 content, which is beneficial to simplify slag structure. Finally, the changed slag structure is in good agreement with corresponding varying viscosity. Copyright © 2020, Northwest Institute for Nonferrous Metal Research. Published by Science Press. All rights reserved.