Modeling of multiphase flow, bubble, and slag entrapment in slab continuous casting

Authors:
  • HXHaitao Xia
    Haitao Xia
  • QLQiliang Li
    Qiliang Li
  • JYJun Yang
    Jun Yang
  • ZFZhengjie Fan
    Zhengjie Fan
  • YXYu Xie
    Yu Xie
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Abstract
In thin slab continuous casting, argon injection is commonly employed to prevent nozzle clogging. However, the bubbles significantly influence the flow field, interface fluctuations, and slag entrainment within the mold. Notably, bubble entrapment at the solidification front may induce quality defects in cast slabs. In this study, a numerical model combining Large Eddy Simulation (LES), Volume of Fluid (VOF), and two-way coupled Discrete Phase Model (DPM) was established, along with a force balance model-based bubble capture criterion, to investigate the internal transient multiphase flow behavior under varying argon injection rates. The results reveal that argon bubbles form vortical structures near the Submerged Entry Nozzle (SEN), constraining flow space in the upper recirculation zone. In the lower recirculation zone, small bubbles generate multiple small vortices through alternating buoyancy and drag forces. While increased argon flow rate elevates absolute bubble entrapment quantity, the relative proportion remains unaffected. Furthermore, argon flow rate substantially impacts interface fluctuation amplitude and slag entrainment. Crucially, the analysis demonstrates that 99% of bubbles and all entrapped slag inclusions are concentrated within 23 and 17 mm below the slab surface, respectively, with argon flow rate exhibiting negligible impact on inclusion entrainment depth. This study enhances understanding of multiphase interaction about molten steel, slag, and argon bubbles, while providing data-driven insights for optimizing trimming strategies in industrial production and a recommended upper limit for argon injection flow rate.

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