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

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 degrees 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.