Motion behavior of micro-bubbles in a delta shape tundish using impact pad

Abstract Micro-bubbles were generated using gas injection through tiny orifices located at the upper part of the ladle shroud, for deep cleaning the liquid steel. An impact pad was employed to improve the dispersion of micro-bubbles in the liquid bath, reduce the collision between bubbles, as well as to achieve the conventional functions of a turbulent inhibitor. A 3-D numerical modeling was developed to predict the flow characteristics and bubble motion behaviors under the effect of the impact pad, with the bubble sizes obtained from the measurements in full-scale water experiments. For comparison, the corresponding numerical simulation was also carried out in the tundish with a conventional turbulent inhibitor. It was found that the impact pad promotes the spreading of micro-bubbles in the tundish bath, which could effectively reduce the coalescence of bubbles, so as to restrain the secondary bubble grow-up. The global efficiency of inclusion removal by bubble flotation was evaluated, considering the mechanism of repeated bubble sweeps in each element. The inclusion removal was raised by 14.33–37.09% due to the extended area of bubbles dispersion, even with the same bubble amount and size.