Influence of substituting B₂O₃ with Li₂O on the viscosity, structure, and crystalline phase of the low-reactive mold flux

The effect of Li₂O instead of B₂O₃ on the viscosity and the melting temperature of the low-reactive mold flux was investigated. The melt structure and precipitation of the crystalline phase were studied using the Raman spectrum and X-ray diffraction to better understand the evolution of viscosity. The viscosity of the mold flux with 2wt% Li₂O and 6wt% B₂O₃ reached the minimum value of 0.07 Pa·s. The break temperature and melting temperature showed a similar trend with the viscosity. With the increase of Li₂O content in the mold flux from 0wt% to 6wt%, the degree of polymerization of aluminate and aluminosilicate network structure increased due to the increasing Li+ released by Li₂O. The addition of Li₂O preferred to associate with Al³⁺ as a charge compensator. The precipitation of the LiAlO₂ crystalline phase led to an increase in mold flux viscosity. Therefore, the content of Li₂O should be controlled below 2wt% to avoid the precipitation of LiAlO₂, which was harmful to the continuous casting of high-aluminum steels.