Bubble behavior under a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle

A novel metallurgy process coupling an annular gas curtain and swirling flow technology at a tundish upper nozzle (TUN) was developed in this paper. The migration and distribution behaviors of bubbles were studied by a 1:2 scale water model, and the effects of the process and structural parameters on the distribution of gas flow and bubble size in the mold were further investigated. The results indicated that most argon bubbles float up in the tundish, forming a complete annular gas curtain around the stopper rod, and a small portion of small bubbles enter the nozzle and mold, which can realize the effect of normal argon blowing at the TUN. The liquid steel passing through the swirl slots can produce a certain swirling flow in the nozzle. Under the action of the centrifugal force of the swirling flow, lightweight bubbles will converge to the centre of the nozzle, which increases the collision and coalescence probability of bubbles. As the flow rate of argon blowing, casting speed, and number and height of swirl slots increase, the argon volume and average bubble size in the mold gradually increase.