Evaluation of Slag Entrainment by Large Argon Bubble Rupturing Using Dynamic Similarity Modeling in Continuous Casting Mold

Slag entrainments in a continuous casting mold are caused by several factors and can generate severe steel product defects. Specifically, the argon bubbles injected from a submerged entry nozzle (SEN) to prevent molten steel solidification at the inner surface of the SEN can cause slag entrainments by altering the meniscus flow pattern and bursting on the slag layer. Most previous studies have focused on the variation in meniscus flows under argon gas injection, considering the argon bubbles as virtual volume particles. However, the effect of argon bubble rupture has not been investigated systematically, although the rupture of argon bubbles larger than 5 mm can directly entrain the slag into the molten steel. Therefore, in this study, we numerically investigated the dynamics in a large argon bubble (LAB) rising through a molten steel and bursting near the slag layer. This study is the first attempt to numerically investigate the effect of LAB rupture on slag entrainment using multiphase simulations based on dynamic similarity modeling. It was found that the strong wake flow behind the rising LAB can cause slag entrainment, and that it is influenced by the bubble Reynolds number, Bond number, and slag layer thickness. Further, slag entrainment occurrence maps were plotted, and the critical LAB sizes for 5 and 10 mm slag layers were revealed to be approximately 10 and 11 mm.