2018 Volume 58 Issue 1 Pages 60-67
The effect of interfacial wettability on the size of gas bubbles releasing from orifices submerged in high velocity cross flow coupled with strong turbulence, was investigated in a full-scale water model of a commercial ladle/tundish/mold system, located at the McGill Metals Processing Centre. The present work attempted to simulate bubble formation in liquid steel passing through a ceramic (non-wetting) ladle shroud, with a high velocity and strong turbulence. This was accomplished by using a hydrophobic coating, sprayed onto the inner surface of the vertical acrylic ladle shroud, forming a contact angle of 150° at the three-phase line of contact, versus an angle of ~45° on the bare plexiglas surface.
As such, the poor wettability of the treated acrylic surface of the ladle shroud led to slight increases in the diameters of micro-bubbles of 8.0%–22.4%, vs wetting systems, depending on gas flow rate and gas injection position. The present results indicate that the cross flows of liquid and their associated kinetic energy of turbulence within a ladle shroud flow can effectively refine bubbles into the micron size range, and prevent bubble growth caused by the poor wettability of liquid steel. Thus, argon gas injection through a ladle shroud could be an effective approach of producing small bubbles in liquid steel, even under the non-wetting conditions associated with such flows, which cannot be achieved by conventional gas curtain technique.