Simulation of flow field and steel/slag interface in the mold region of a thin slab steel continuous caster with tetra-furcated nozzle

[Display omitted] ► 3-D flow field model of crystallizer system in a thin slab steel continuous caster is presented. ► There are asymmetries between two sides of the flow. ► Increasing casting speed and decreasing submergence depth can increase the instability of liquid surface. ► Higher submergence depths give suitable waves and prevent defects. A three dimensional steady flow field model in the mold region of a thin slab steel continuous caster is presented using real geometrical dimension starting from the inlet port of the nozzle. The results indicate a special flow pattern in the caster while using a tetra-furcated nozzle. The fluid pattern in the mold region is shown to have two large downward and upward recirculation zones with a classic double-roll and two small vortices generated by the upward flow from the upper ports of the submerged entry nozzle. The flow pattern agrees well with the real observation obtained by full scale water model. This study investigates the interface wave behavior and its mechanism that leads to the breakup of the steel/slag interface, and thus the induction of impurities inside the final steel product. It is shown that a maximum wave height occurred because of the fluid contact from the upper ports. A critical casting speed was defined as the casting speed lead to wave instability, mostly associated with emulsification phenomena.