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

Estimation of changes in the composition and physical properties of mold flux during continuous 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 the throughput of the molten steel affect the rate of increase of the Al2O3 content in the mold flux. (3) The change of the physical properties of the mold flux was estimated based on the changes in the flux composition. 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.