Structural Behavior of Al 3+ in Mould Flux Glasses of CaO–SiO 2 –Al 2 O 3 –Na 2 O–CaF 2 System

Quenched glass samples of CaO–SiO 2 –Al 2 O 3 –Na 2 O–CaF 2 system were prepared within the composition of continuous casting mould flux, and the chemical composition and Raman spectra were detected subsequently. The degree of polymerization and structural behavior of Al 3+ were investigated on the base of the quantitative calculation of structure species. The experimental data showed that the dominant structure species are Q i ( i  = 0, 1, 2) of the Si–O tetrahedrons in the liquid mould flux, and the degree of polymerization decreases with the increasement of basicity and the decreasement of Al 2 O 3 content. Al–O tetrahedrons and Al 3+ cations coexist in the liquid mould flux, and the mole fraction of Al–O tetrahedrons increases with the increasement of basicity and Al 2 O 3 content. Under the condition of the mole ratio Al/(Al + Si) < 0.19, the structural behavior of Al 3+ is stable in the liquid mould flux. Considering the variation of mould flux composition during Al‐killed steel continuous casting process, the initial content of Al 2 O 3 and SiO 2 in the mould flux should be controlled appropriately according to the transition point Al/(Al + Si).