• mould fluxes;
  • high aluminum TRIP steel;
  • CaO–SiO2 slag system

Due to its high content in Al-TRIP steel, Al is easily to react with SiO2 in mould fluxes during the continuous casting process, which results in the drastic decrease of SiO2 content, increase of Al2O3 content and the basicity (R = CaO/SiO2), respectively. The magnitude change of physical properties of the slag can affect continuous casting process and the surface quality of slabs. Especially, the change of basicity influenced the crystallization property, and thus influenced the heat transfer of mould fluxes. In this study, three CaO–SiO2 based mould fluxes A, B, and C with different basicity (A was the originally used mould fluxes, B and C were the newly developed mould fluxes) were used to cast high aluminum TRIP steel with 0.80–1.00% Al and 0.085–0.115% carbon. The property change of mould fluxes and its influence on the quality of the slab surface were evaluated. It is indicated that appropriate increase of the basicity of base mould fluxes was beneficial to improve the crystallization property of spent slag and for the inhibition of heat transfer so as to reduce the occurrence of cracking and depression on the slab surface effectively. And also, it can shorten the time of slag–metal reaction reaching dynamic equilibrium and the length of transition slab with defect on surface in the start casting stage. Accordingly, the quality of slab cast by mould fluxes C was the best.