Effect of basicity on crystallization,heat transfer,and structure of mould flux for high-speed thin slab continuous casting

Abstract

To solve the problem of high longitudinal cracks on the surface of slab during high-speed thin slab continuous casting, in this study, the heat transfer capacity of mould flux was reduced by increasing the basicity, and the influence mechanism was revealed. According to our results, when the basicity increased from 1.60 to 1.80, the crystallization temperature range of the mould flux broadened, the critical cooling rate increased, and the crystallization activation energy decreased; thus, increasing the basicity promoted the crystallization of the mould flux. Simultaneously, increasing the basicity reduced the heat flux density of the slag film, promoted the precipitation of the main mineral phase cuspidine (Ca₄Si₂F₂O₇) in the slag, and reduced the heat transfer performance. FTIR and Raman spectra demonstrated that increasing the basicity reduced the aggregation of molecular clusters in the slag and increased the crystallization rate, which was beneficial to the crystal growth but detrimental to the heat transfer performance.