Estimation of Changes in Content and Characteristics of Mold Flux during Continuous Casting

Estimation of changes in mold flux composition and physical properties during casting was investigated for control of slab surface quality. In this study, 0.7 mass% Al steel and normal Al-killed steel were cast with three kinds of mold flux having Al2O3 contents of 1.3 to 6.0 mass% and different basicities. The results can be summarized as follows:(1) The Al2O3 content of these mold fluxes increased to 30 mass% during continuous casting. The composition change of the mold flux can be reproduced by the Equilibrium Effective Reaction Zone Model (EERZM) by fitting parameters, referring to the casting results.(2) The analysis by EERZM revealed that the viscosity of the mold flux and throughput of the molten steel affect the rate of increase of the Al2O3 content in the mold flux.(3) The change of mold flux physical properties was estimated based on flux composition changes. The change of the crystallization temperature and main crystal can be estimated by FactSage.(4) Mold flux viscosity can be estimated by revising the modified Iida’s equation, which considers the effect of Al2O3 as an amphoteric oxide.