Evaluation of Mold Flux for Continuous Casting of High-Aluminum Steel

Study of mold fluxes for continuous casting of high-aluminum steel has attracted increasing attention due to severe reaction between aluminum in liquid steel and silica in the flux which results in changes in composition, properties and performance of the flux and adversely affects slab quality. This research began with sampling during the casting process of high-Al nonmagnetic steel 20Mn23AlV to evaluate potential problems. A mold flux was developed in which SiO2 was partially replaced with Al2O3. Different compositions including CaO/Al2O3, fluoride-free and low-fluoride lime-alumina-based fluxes were evaluated with respect to their influence on flux viscosity, crystallization and subsequent effects on steel quality. It was concluded that mold flux with CaO/Al2O3 ratio in the range 1.1 to 1.6 and characterized by low viscosity, low initial crystallization temperature and good heat transfer properties was appropriate for casting of high-aluminum steel. A viscosity model with high reliability in predicting the viscosity of mold flux containing high Al2O3 was also established.