Effect of TiO2 substituting SiO2 on the rheological and crystallization behavior of mold slags for casting Ti-containing steel

Abstract

In the current study, the influence of TiO 2 substituting SiO 2 on the rheological and crystallization behavior of mold slags for casting Ti-containing steel was investigated through the measurement of the viscosity-temperature relationship, crystallization process and initial crystallization temperature. The structure of molten slags from the Raman spectrum and other parameters (NBO/T and Optical basicity) was compared to explain the difference of slag properties. With the substituting of SiO 2 by TiO 2 in slags from 5% to 20%, the viscosity of these slags at 1573 K decreased from 0.36 Pa s to 0.10 Pa s, and the viscous flow activation energy below the break temperature had the tendency to decrease. With the increase of the TiO 2 /SiO 2 ratio from 0.25 to 4.00, the initial crystallization temperature of slags increased and the crystallization of slags were enhanced, which was related to the difference of the crystallization mode and the precipitation of dispersed crystals as nuclei. With the substituting of SiO 2 by TiO 2 , the parameter NBO/T and optical basicity of molten slags increased, the complex network structure by the Raman spectra depolymerized gradually and the degree of polymerization decreased, which was related to the destruction of silicate/aluminate structure by the addition of TiO 2 in slags. Hence, the substitution of SiO 2 by TiO 2 in slags simplified the network structure of mold slags, then lowered the viscosity and promoted the crystallization of slags.