Effect of Li₂O on the Behavior of Melting, Crystallization, and Structure for CaO-Al₂O₃-Based Mold Fluxes

The effect of Li₂O content on the behavior of melting, crystallization, and molten structure for CaO-Al₂O₃-based mold fluxes was investigated in this article, through use of single hot thermocouple technology (SHTT), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray diffraction (XRD). The SHTT results showed that the melting temperature range of the designed mold fluxes decreases and the crystallization of mold fluxes is inhibited first and then becomes enhanced when the Li₂O content increases from 1 to 6 mass pct. The FTIR and Raman spectroscopy results suggested that Li₂O could release O²⁻ ions to break the complex Al-O-Al structural unit into Al-O⁻ structure. Meanwhile, Li₂O could also stabilize the structural unit of Si-O-Al by link aluminate and Q ₀ ^Si structure through providing Li⁺ ions to merge into the network and compensate for the charges between Al³⁺ and Si⁴⁺. Besides, the XRD results indicated that the precipitation of LiAlO₂ in molten slag would enhance the crystallization behavior of mold flux when Li₂O content is over 4.5 mass pct.