Non‐Isothermal Crystallization Kinetics of Mold Fluxes Containing Li2O for High Aluminum Steel Casting

When continuously casting high Al steels, CaO–SiO2 based mold fluxes can be easier for sequence casting, but due to the significant reactions of the Al in the metal with SiO2, slab surface quality is not desirable. When increasing basicity of CaO–SiO2 based mold fluxes, slab surface quality can be improved, but thick slag rim can easily be formed during cooling process. Therefore, non-isothermal crystallization kinetics of mold fluxes used for high Al steels are studied to optimize the crystallization behavior of “working” fluxes. Results indicate that the addition of Li2O can decrease crystallization temperature and crystallization rate within the range of Na2O studied. The Avrami exponent determined by Avrami equation indicates that disk-like growth type and spherulitic-like growth type are the main mechanisms in crystallization, which is consistent with results observed under SEM. When mold flux contains 8% Na2O and 4.5% Li2O, the effective activation energy is between −299 and −488 KJ mol−1. When mold flux contains no Na2O and 6.5% Li2O, the effective activation energy is between −266 and −414 KJ mol−1, which indicates that Na2O-free mold fluxes containing high Li2O is beneficial for improving crystallization characteristics and realizing sufficient lubrication.