Effect of CaO/SiO₂ and Al₂O₃/SiO₂ Mass Ratios on Structure and Viscosity of Mold Flux for Continuous Casting High‐Mn High‐Al Steel

During continuous casting process of high‐Mn high‐Al steel, soluble Al in the steel typically reacts with SiO 2 in the mold flux, resulting in a decrease in SiO 2 content and an increase in Al 2 O 3 contents in the flux. The structure of slags with varying CaO/SiO 2 and Al 2 O 3 /SiO 2 mass ratio is investigated using Raman spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. In the deconvolution results of Raman and NMR spectra, it is shown that the relative fractions of and significantly increase, while and gradually decrease with an increase in the CaO/SiO 2 mass ratio from 0.52 to 1.02, resulting in depolymerization of the bridge oxygen structure. The silicon–oxygen tetrahedron transforms into aluminum–oxygen tetrahedron when the Al 2 O 3 /SiO 2 mass ratio increased from 0.05 to 1.01. The viscosity of the slags with varying composition from 1573 to 1373 K is investigated. In the results, it is shown that with an increase in the CaO/SiO 2 mass ratio, the viscosity decreases, and the complex SiO network structure is depolymerized. The viscosity decreases first as the Al 2 O 3 /SiO 2 mass ratio increases from 0.05 to 0.24 and then increases as the mass ratio from 0.24 to 1.01, with the network formers transfer from SiO to SiAlO structures.