Numerical Investigation on Gas Bubbling Assisted Inclusion Transport and Removal in Multistrand Tundish

In continuous casting, the molten metal quality in the mold is affected by flow pattern, temperature distribution and inclusion transport in the multistrand tundish. Natural convection due to thermal buoyancy directly influences these parameters and with gas bubbling, further improvisation can be made. In the present work, numerical investigation of the effect of thermal buoyancy is carried out to examine the flow field, temperature distribution and inclusion trajectories. Further, gas bubbling curtain modeling using the Euler-Euler approach is performed for the different locations on the bottom wall of the tundish and quantitative analysis of tundish performance is presented using residence time distribution (RTD) curves. The results show that big circulation loop generated due to thermal buoyancy assists in inclusion removal and mixing at each outlet. Gas bubbling increases the molten metal flow velocity in the central region of tundish, leading to a decrease in the dimensionless number Gr/Re² near the outlets which are far away from the inlet of the tundish i.e. outlet 2 and outlet 3. Hence, the dominance of natural convection decreases. The inclusion removal rate is found to increase significantly as the circulation loop formed at each side of the curtain forces them upward direction. However, the reported inclusion removal rate in gas bubbling cases is found to be independent of particle size and curtain location.