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

Abstract

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 CaF2, that the loose CaF2 cluster structure is facilitated. Meanwhile, with the addition of F− within 10 wt pct, the crystalline phase changes from BaAl2O4 to Ca12Al14O33 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 CaF2 and the intensity of the crystal peak is heightened, making Tbr enhance. Moreover, the apparent crystallization ratio also decreases and then increases.