Effect of B2O3 on the structure of CaO-Al2O3-B2O3 ternary melts: A molecular dynamics simulation

•The effect of B3+on atomic cluster distribution, oxygen distribution and atomic diffusion capacity were determined by a molecular dynamics simulation.•B-O was preferentially involved in the Al-O network structure rather than by separate B-O network. B3+ tended to enter the Al-centered atomic cluster Q4.•The formation of BⅢ-O-AlⅣ structure prevented the extension of the complex Al-O three-dimensional network resulting in the increase of bridge oxygen while the atomic cluster Qn in the high polymerization state decreased overall. CaO-Al2O3-based mold flux has been a good candidate for high aluminum steel casting. However, the high melting temperature, great viscosity and complexed crystallization of CaO-Al2O3 slags had affected the controlling of heat transfer and lubrication between mold flux and steel. B2O3 as a good additive, can effectively adjust the properties of slag. Therefore, the effect of B2O3 on the structure of CaO-Al2O3-B2O3 system were investigated by molecular dynamics simulation. The results showed that Al3+ was dominated by [AlO4] tetrahedra (about 80%), with [AlO5] and [AlO6] as the rest. B3+ mainly formed two-dimensional layered [BO3] and [BO4] tetrahedral. As the increase of B2O3, B3+ tended to form more [BO3] and combined with [AlO4] to form the BⅢ-O-AlⅣ linkage, which prevented the extension of the Al-O three-dimensional network, and reduced the degree of network polymerization, and resulting in the decrease of viscosity. This work would be helpful to optimize the design of CaO-Al2O3 mold flux.