Development of a Thermodynamic Database for Mold Flux and Application to the Continuous Casting Process

Abstract

A thermodynamic database for the oxyfluoride system CaO–MgO–Al₂O₃–SiO₂–Na₂O–K₂O–Li₂O–MnO–FeO–F has been developed based on the critical evaluation and optimization of all available experimental thermodynamic and phase diagram data. The developed database can be used for phase diagram and equilibrium solidification calculations for multicomponent systems. Such accurate database with high predictability capability assists in understanding the crystallization behavior of mold fluxes. In addition, a kinetic model was developed to simulate the interactions between the mold flux and molten steel using effective equilibrium reaction volumes combined with the thermodynamic database. The kinetic model successfully reproduced the significant Al₂O₃ accumulation observed when casting high Al steel with CaO–SiO₂ based mold flux. Equilibrium solidification calculation performed on the Al₂O₃-rich mold slag revealed detrimental changes in the solidification temperature, the primary phase and the evolution of the liquid fraction with temperature.