Experimental Study on Bubble Entrainment by a Free Fall Jet in an Argon-Filled Continuous Casting Tundish

Inert gas entrainment by the impact of free fall jet can avoid the bubble grow-up on nonwetting interface between liquid steel and refractory gas nozzle, which produces bubbles as small as 0.37 mm for deep cleaning the liquid steel in an argon-filled tundish. The time-dependent vibration of free fall jet is described by a high-speed camera combined with image postprocessing software. The effect of liquid flow rate and free fall length on jet vibration is investigated. The equivalent surface roughness is proposed to characterize the surface wave of free fall jet without fixed amplitude and frequency. The entrained gas flow rate shows a good correlation with the equivalent surface roughness. Gas entrainment cannot happen with a free fall jet shorter than 2 mm, as the jet vibration is insufficient to make the bubbles separate from the gas sheath. The surface fluctuation caused by the impact of free fall jet can be well isolated within a submerged shield that remains a stable slag layer outside of the shield. Besides, the strong mixing flow caused by free fall jet is beneficial to dissipate the turbulence kinetic energy of the entry flow, which improves the tundish flow field.