Effects of B<sub>2</sub>O<sub>3</sub> and CaO/Al<sub>2</sub>O<sub>3</sub> on Structure of CaO–Al<sub>2</sub>O<sub>3</sub>–B<sub>2</sub>O<sub>3</sub> System

CaO–Al2O3-based mould fluxes are the most significant slag systems for the continuous casting of high-Al steel. In this study, to investigate the structure of the CaO–Al2O3–B2O3 system, molecular dynamics simulation and infrared spectroscopy experiments with different amounts of B2O3 and CaO/Al2O3 ratio were carried out. The results showed that the structural unit of B–O and Al–O are of great stable while B atom is easier to bond with O atom than Al, and [BO3]3− trihedron is more stable than [AlO4]5− tetrahedron. With the content of B2O3 increases, the increased [BO3]3− trihedral structure units can balance the excessive negative charges in [AlO4]5− tetrahedron structure, and Al2O3, acts more acid in a highly alkaline surrounding, can absorb O2− and results in forming [AlO5]7− structure at high CaO/Al2O3 ratio, which promotes the transformation of Onb into Ob, while CaO results in an increase in the content of Onb with the increase of CaO/Al2O3 ratio. The results of infrared spectrum are consistent with simulation results that B2O3 addition promotes the complexity of the network structure, and the depolymerization of the large complex network structure with increased CaO/Al2O3 ratio.