Effects of argon blowing at tundish upper nozzle on multiphase flow behavior in nozzle

In continuous casting, the argon blowing at the tundish upper nozzle is usually used to prevent nozzle clogging, whose effect is closely related to the migration of argon bubbles and the flow behavior of the liquid steel in the nozzle. Here, to investigate the effects of argon blowing at the tundish upper nozzle on multiphase flow behavior in nozzle, a three-dimensional model of the tundish–nozzle–mold was established for numerical simulation. The results indicate that the argon bubbles injected from the inner wall of the tundish upper nozzle first move downward along the nozzle wall under the action of the liquid steel. As the distance from the tundish upper nozzle increases, the argon bubbles gradually diffuse to the center of the nozzle. Compared with no argon blowing, the liquid steel velocity increases in the center of the nozzle and decreases near the wall with argon blowing. With increasing the argon flow rate, the concentration of bubbles in the nozzle increases, and the process of bubble group diffusion to the center region of the nozzle speeds up. This in turn increases the liquid steel velocity at the center of the nozzle but reduces near the wall. With increasing the casting speed, the concentration of bubbles in the nozzle decreases, the length of the bubble group near the nozzle wall is extended, and the liquid steel velocity at the center region and near-wall region of the nozzle increases. The mechanism of argon blowing at the tundish upper nozzle to prevent nozzle clogging is mainly realized by the isolation effect of the argon bubble group on the inner wall of the nozzle.