Water model and CFD studies of bubble dispersion and inclusions removal in continuous casting mold of steel

Abstract

A water model study was undertaken to investigate bubble dispersion and inclusions removal by bubble adhesion in continuous casting mold. The water flow rate was varied in the range of 37-74 L/min, which is equivalent to 1.0-2.0m/min of the casting speed in continuous casting process. The gas flow rate was varied in the range of 0-2.5 L/min. Silver coated hollow glass beads (SCHG) and plastic particles were used to imitate the inclusions and to investigate the effect of wettability, i.e., contact angle of the inclusions with liquid, on inclusion removal by bubble adhesion. Effect of gas and water flow rates on bubble dispersion in the mold was systematically determined. Inclusion removal at different gas and water flow rates was quantitatively determined. It was identified that the wettability of inclusions with liquid was a decisive factor in inclusion removal: with low wettability, i.e., high contact angle, removal efficiency increased with increasing gas and liquid flow rates, whereas removal efficiency was hardly affected by gas flow rate with high wettability, i.e., low contact angle. To interpret the results of the water model experiments, various computational fluid dynamics (CFD) models which had been reported were applied. None of them was able to represent the experimental results within an acceptable discrepancy. Two new CFD models, which employed a modified Reynolds number and force field theory around the bubble, were developed to simulate bubble dispersion and inclusion removal, respectively. The results indicated that these models could simulate bubbles dispersion and inclusion removal and showed reasonable agreement with results of water model in continuous casting mold. © 2006 ISIJ.