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.