Influence Mechanism of F− on the Structure and Properties of Aluminate-Based Mold Flux

The spectral experiment, hemispherical melting point apparatus, rotating cylinder method, and four-probe method were conducted to measure the structure, melting temperature, viscosity, and electrical conductivity of aluminate slag. The results show that with F − content increase from 2 to 10 wt pct, the hemispherical melting point depresses, and the structure depolymerizes, leading to reduce of viscosity and augment of electrical conductivity. With further increase of F − content from 10 to 14 wt pct, both the hemispherical melting point and the network structure associated with Si and B polymerization turn upward, so the viscosity enhances. However, the electrical conductivity continuously augments due to the diluent effect of CaF 2 , that the loose CaF 2 cluster structure is facilitated. Meanwhile, with the addition of F − within 10 wt pct, the crystalline phase changes from BaAl 2 O 4 to Ca 12 Al 14 O 33 and the intensity of the Bragg diffraction peak decreases, resulting in a decline in the breaking temperature ( T br ) of apparent viscosity–temperature curve. When the F − content exceeds 10 wt pct, the crystalline phase transforms into CaF 2 and the intensity of the crystal peak is heightened, making T br enhance. Moreover, the apparent crystallization ratio also decreases and then increases.