The high content of aluminum in the steel reacts with the CaO-Si2O-based mold fluxes, resulting in deterioration of the mold slag physical and chemical properties, which cannot be applied to the continuous casting molten slag casting process of high-Mn high-Al steel Herein, the thermodynamic and structural properties of low-reactivity CaO-Al2O3-based mold fluxes were investigated. The thermodynamic properties were studied based on the first principles of quantum mechanics. The results show that the formation of stable structures of B-O and O-B-O in the mold fluxes was beneficial to reduce the probability of structural interconnection, degree of polymerization, and viscosity of the molten slag. The increase in the ratio of CaO/Al2O3 = 0.88–2 led to an increase in the O2− concentration. O2− entered the [AlO4] structure to form a stable structure of [AlO6] and [AlO5], wherein [AlO6] was more stable than [AlO5], reducing the degree of polymerization of the network structure. When cosolvent content B2O3 = 2%–10%, a simple layered structure of [BO3] was formed, and the particle migration resistance, break temperature, and viscous activation energy of the mold fluxes were reduced, while the corrected optical basicity of mold fluxes was gradually increased.

Since CaO-Al2O3-based mold fluxes are one of the most important mold flux systems in metallurgic processes, it is important to explore their structure characteristics and viscosity. Molecular dynamics simulation is performed to study the effect of w(CaO)/w(Al2O3) ratio on both the structural and viscosity properties of CaO-Al2O3-based mold fluxes. A systematic analysis of the structure and thermodynamics on CaO-Al2O3-based mold fluxes is carried out, and it is well known that the viscosity of mold fluxes is related to the structure. The results show that the formation of stable structures of Si-O in the mold fluxes was beneficial to reduce the probability of structural interconnection, degree of polymerization, and viscosity of the molten slag. In the cationic structure, the contents of Ca-O-Al and Ca-O-Si are more stable, the interconnection of the Ca-O-Al and Ca-O-Si network weakens, and the viscosity decreases. The tetrahedra [AlO4] and [SiO4] have similar structures, but they exhibit different thermodynamic and physical properties. Viscosity test shows that CaO/Al2O3 = 0.88–2 continuously increased, when the cosolvent content Li2O = 1%–4%, CaO-Al2O3-based mold flux viscosity decreased, the degree of network structure polymerization decreased, and the complex structure depolymerized. Increasing the water content in the cosolvent is beneficial to reduce the viscosity of the crystallizer.

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