Melt structure of calcium aluminate-based non-reactive mold flux: Molecular dynamics simulation and spectroscopic experimental verification

•In this paper, a non-reactive continuous casting mold powder without SiO2 is proposed, which fundamentally avoids the interface reaction between [Al] in molten steel and SiO2 steel slag in mold powder during the production of high aluminum and high manganese steel.•The effect of alkali metal oxides (Na2O and Li2O) on the structure of non-reactive mold flux was investigated.•A systematic study of the melt structure of non-reactive protective slag using a combination of molecular dynamics calculations and spectroscopic experiments, which is innovative. In this study, a combination of molecular dynamics (MD) simulations and spectroscopic experiments was used to investigate the effect of alkali metal oxides (Na2O and Li2O) on the structure of calcium aluminate-based non-reactive mold flux. The results of the MD simulations show that Al-O bonding forms the basis of the slag structure. The increase of Y2O (Y represents Na or Li) promotes the formation of AlIV in the melt and improves the stability of the Al-O structure, while the polymerization of the melt and the complexity of the network structure show a decreasing trend. Raman spectroscopy results show that the characteristic peaks move to lower wave numbers with the increase of Y2O, and the polymerization degree and complexity of the network structure of the slag also decrease. MAS-NMR results show that there are multiple coordination states of Al3+ in the mold flux. With the increase of Y2O content, the content of AlIV and [AlO3F] in the mold flux increases, indicating that the Al-O network structure becomes more stable. The experimental results are in agreement with the MD simulation results. The findings of this work provide a detailed study for a deeper understanding of the structure and properties of non-reactive mold flux.