Effect of lepidolite on melting, viscosity and structure of CaO-SiO2 based melt

It will be an economic, environmental-friendly and energy-saving way to utilize lepidolite as a substitution of industrial grade lithium carbonate for preparation of commercial mold flux. Therefore, the melting behavior, viscosity and melt structure of mold fluxes with different lepidolite content were investigated in this study. The results show that the initial melting temperature of the fluxes increases from 1278.4 to 1301.2 K, meanwhile the complete melting temperature increases from 1622.0 to 1674.4 K with the addition of lepidolite from 15.10 to 37.80 wt%. The viscosity of mold fluxes at 1573 K increases from 0.12 to 0.44 Pa s, whereas the break temperature reduces from 1467.7 to 1386.9 K with the increase of lepidolite. The melt structure analyses suggests that the simple structural units, such as Q0, Q1, Q2 and [AlO4]5-- tetrahedral asymmetric stretching reduce; while the complex structural units, like Q3, Q4, [AlO4]5-- tetrahedral symmetric stretching and Al-O-Si bending increase with the addition of lepidolite. These changes suggest that the free oxygen transforms into bridging oxygen and non-bridging oxygen, and the structure of melt becomes more complex when lepidolite is added in the flux.