Microscopic Analysis of the Effects of Ce2O3 and CaF2 on the Structure and Properties of Mold Flux for Rare Earth-Containing Steel Continuous Casting

The effects of Ce2O3 and CaF2 on the microstructure of silicate-based mold flux were investigated using an integrated approach combining molecular dynamics (MD) simulations with viscosity testing, SEM-EDS, and XRD analysis. The structural origin of changes in viscosity and crystallization behavior was revealed. It was found that the joint addition of CaF2 and Ce2O3 to the silicate melt leads to a synergistic effect; CaF2 acts as a diluent within the silicate network, while O2− introduced by Ce2O3 promotes the depolymerization of the complex [SiO4]4− network. As a result, highly polymerized structural units (Q2, Q3, and Q4) transform into less polymerized ones (Q0 and Q1), reducing the overall degree of polymerization and enhancing slag fluidity. Moreover, the preferential formation of [SiO4]4−–Ce3+–F− and [SiO4]4−–Ca2+–F− coordination structures replaces the original [SiO4]4−–Ce3+ and [SiO4]4−–Ca2+ linkages. This structural rearrangement facilitates the formation of low-melting-point phases during cooling, thereby suppressing the crystallization tendency and improving the stability of viscous properties of the mold flux. These findings provide theoretical insight for the design of high-performance fluxes used in rare earth-containing steel continuous casting.