Effect of B₂O₃ on Melting Temperature, Viscosity and Desulfurization Capacity of CaO–based Refining Flux

摘要

Fluorite is widely employed as fluxing agent in metallurgy flux, which inevitably leads to serious fluorine pollution. In this work, B_(2)O_(3) is used as fluxing agent of CaO–based refining flux to substitute for CaF_(2) so as to decrease the melting temperature and to improve the speed of slag forming and the refining efficiency. The effects of B_(2)O_(3) on the melting temperature, viscosity and desulfurization capacity of CaO–based refining flux were investigated. The results indicate that the fluxing action of B_(2)O_(3) is better than that of CaF_(2) and Al_(2)O_(3). For the high basicity CaO–based refining flux (mass ratio of CaO/SiO_(2) is 5.0–8.75), when CaF_(2) is substituted with B_(2)O_(3), the melting temperature can be decreased remarkably. Especially, when the mass ratios of CaO/Al_(2)O_(3) and CaO/SiO_(2) are in range of 1.1–4.0 and 5.25–8.0, respectively, the flux melting temperature is lower than 1300°C. At the same time, the temperature range, in which the flux viscosity is low, is expanded as well as the stability of flux viscosity varying with temperature is improved obviously. These variations of flux properties are favorable for refining process. The results of experiments on sulphur partition equilibrium between metal and flux indicate that the desulfurization capacity of flux can be improved markedly when CaF_(2) is substituted with equal mass of B_(2)O_(3). When 4 mass% B_(2)O_(3) is employed as fluxing agent and the mass ratio of CaO/Al_(2)O_(3) is in the range of 1.5–7.0, the final sulfur content of metal can be controlled lower than 0.004%.