Viscosity effect of titanium pickup by mould fluxes for stainless steel

Abstract

Mould flux samples from an operating continuous caster showed a steady state increase in titanium oxide content of 3-4% for a titanium stabilised ferritic stainless steel and about 6% for a titanium stabilised austenitic stainless steel. Owing to the reduction of silica the flux basicity increased from 0.8 to 0.9, and from 0.95 to 1.2, for the ferritic and austenitic steels, respectively. Similar changes in composition were found for mould shims, which had been recovered from the mould after casting the ferritic steel. The increased titanium oxide content caused a decrease in the flux viscosity, for the original basicity. However, when the flux basicity was increased from 0.95 to 1.2, the apparent viscosity of the mould flux of the austenitic steel increased markedly, for 10% TiO2 and temperatures of 1250°C and below. Precipitation of perovskite was found to be responsible for the higher apparent viscosity.