Effect of TiO2 on the structural properties and viscosity of CaO-SiO2-8.25 %MgO-15 %Al2O3-TiO2 slags

Abstract

As a raw material for ironmaking, vanadium-bearing titanomagnetite will leads to an increase in the TiO2 content of blast-furnace slag and deteriorates the metallurgical properties of the slag. In this study, the effect of TiO2 content on the viscosity of CaO-SiO2–8.25 %MgO-15 %Al2O3-TiO2 slag system at fixed w(CaO)/w(SiO2) ratio of 1.2 was investigated, and Raman spectroscopy focusing on the relationship between the structure of high TiO2-bearing blast furnace slag and viscosity was performed. The findings showed that under the experimental condition, the viscosity of slag decreases with the increase of TiO2 content over a range of 20 to 35 %. The melting temperature of slag increases first and then decreases after w(TiO2) is higher than 30 %. The viscous-flow activation energy of slag decreases with the increase of TiO2 content, which has a concomitant variation corresponding with the results of the effect of TiO2 on viscosity. The analysis of Raman spectroscopy results reveals that the blast-furnace slag system is dominated by [SiO4]4- network structure. As the TiO2 content increases, more and more Ti4+ enters the silica-oxygen tetrahedral network structure, disrupting the Si-O-Si bond to form the [TiO4]4- structural unit and a small portion of the [TiO6]8- structural unit. The NBO/Si value of the Si4+ in the tetrahedron unit as an index for the degree of depolymerization of slags increased from 1.62 to 2.60 as the TiO2 content increased, the slag structure was gradually simplified and the slag viscosity was gradually decreased.