Computational Insight into the Thermal Conductivity of CaO-SiO2-Al2O3-MgO-Na2O Melts

CaO-SiO₂-Al₂O₃-MgO-Na₂O (CSAMN), as a basic system, has been extensively studied and widely applied in the field of mold flux. The thermal conductivity parameter of melt film as a critical indicator affects the heat transfer during the continuous casting process. However, many details of the CSAMN thermal conductivity still remain unclear. Herein, the thermal conductivity of the molten CSAMN system under different compositions was calculated at 1773 K based on equilibrium molecular dynamics simulation. The structure of the CSAMN system was further investigated to explore the relationship between composition and thermal conductivity. The results show that the thermal conductivity of CSAMN melt has a significant positive correlation with the CaO/SiO₂ (C/S) mole ratio. The Si-O/Al-O network depolymerizes with an increase in the C/S mole ratio and polymerizes with the increasing Al₂O₃/SiO₂ (A/S) mole ratio. The bridging role of Ca²⁺ is enhanced with the increase in the C/S mole ratio and slightly decreases with the increasing A/S mole ratio. The connection of the Al-O and Si-O network and the bridging role of Ca²⁺ promote phonon transmission, which in turn increases the thermal conductivity of the CSAMN melt.