Investigation on viscosity of mould fluxes during continuous casting of aluminium containing TRIP steels

Abstract

Transformation induced plasticity steel with a high content of Al (Al-TRIP) is an advanced high strength steel. The reaction between Al and SiO₂ would lead to compositional changes in mould fluxes, which results in a decrease in SiO₂ content and an increase in Al₂O₃ content, and influences the physical properties of the molten fluxes. In the present study, the changes of viscosities of a series of mould fluxes with different additives and addition amounts were examined by a rotating viscometer and the crystals in the D series mould fluxes were analysed by scanning electron microscopy and X-ray diffraction. The results show that (a) the Al₂O₃ in mould fluxes containing Li₂O presents amphoteric characteristic; (b) the viscosity of the fluxes with 8% B₂O₃ decreases with the increase in w(Al₂O₃)/w (SiO₂) ratio, the result shows that the Al₂O₃ presents alkaline; (c) the viscosity of flux containing both 4% Li₂O and 5% B₂O₃ changes a little with the increase in w(Al₂O₃)/w(SiO₂) ratio. When the Al₂O₃ content is 30%, the viscosity is 0·204 Pa s and the break temperature is 1130°C; (d) mould fluxes used for Al-TRIP steel precipitate CaF₂ crystals; (e) base on the Riboud model, a suitable viscosity mathematical model for the mould fluxes with high Al₂O₃ content is established.