Influence of B2O3 on the Viscosity and Melt Structure of CaO-SiO2-M2O (M = Li, Na)-Based Slags

In the process of continuous casting, especially high-speed continuous casting, the inflow state of the mold flux is particularly important. The fluxing agent is one of the most important factors affecting the flow state. The influence of the typical fluxing agent B2O3 on the viscous characteristics and melt structure of the fluorine-free CaO-SiO2-M2O (M = Li, Na) system was analyzed. The following conclusions were drawn. In the CaO-SiO2-Na2O slags, with the increasing addition of B2O3, the viscosity, breaking temperature, and polymerization degree of the slag show a gradually decreasing trend. When the mass fraction of B2O3 increased from 0 to 10%, the increase in two-dimensional [BO3] structural units played a dominant role. When the mass fraction of B2O3 reached 15%, the network was affected by the increase in [BO3] and the low-polymerized [SiO4] tetrahedrons. The CaO-SiO2-Li2O slag system had a lower breaking temperature due to the formation of phases such as Li2O·2B2O3, of a low melting temperature. The initial degree of depolymerization of the network was high. Upon increasing the addition of B2O3, the relative proportion of the network modifier structural units significantly increased, resulting in the enhanced instability of the network structure. As a result, the effect of [SiO4]-polymerization was stronger than that of [BO3]-depolymerization in maintaining the stability of the network structure.