Numerical Simulation of Coupled Ar/N₂ Bubbles and Steel-Slag Interface Behavior in an Enamel Steel Continuous Casting Mold

To address the severe surface defects such as subcutaneous blowholes and inclusion entrapment that are prone to occur during the continuous casting of enamel steel, a mathematical model of the steel-slag-gas behavior in the mold was established using the volume of fluid (VOF) method and the Lagrangian discrete phase model (DPM). The coupled behavior of argon and nitrogen bubbles and its influence on bubble distribution, molten steel flow, slag-metal interfacial tension, and bubble motion in the mold were investigated. The results indicate that argon bubbles are mainly distributed near the submerged entry nozzle (SEN), whereas nitrogen bubbles predominantly accumulate at the steel-slag interface. As the argon blowing rate increases, the flow velocity in the upper recirculation zone near the tundish nozzle increases from 0.04 m/s to 0.42 m/s, accompanied by an increase in both the bubble escape rate and the capture rate. When the interfacial tension decreases, the maximum flow velocity at the steel-slag interface can reach 0.14 m/s, and the maximum interface wave height reaches 1.98 mm; consequently, the bubble escape rate increases while the capture rate decreases. Therefore, the numerical simulation results demonstrate that the argon blowing process is prone to inducing slag entrapment and blowhole defects, while variations in interfacial tension further aggravate the occurrence of slag entrapment. By quantitatively identifying the risk range of bubble runaway and the influence of interfacial tension on the steel-slag interface through numerical simulation, this study provides a theoretical basis for optimizing the argon blowing regime and reducing defect rates, thereby decreasing the frequency of defective products in actual production and supporting the efficient and green transformation of the steelmaking process.