Bubble Formation by Short Plunging Jet in a Continuous Casting Tundish

Abstract

A short plunging jet technique was developed to produce small bubbles in continuous casting tundish, with argon sealing, in order to promote the removal of inclusions smaller than 50 μm. The liquid steel coming out of the ladle shroud is accelerated and vibrated by gravity, leading to gas entrainment. This novel approach is free from bubbles growing along the nozzle surface due to the poor wetting condition, which is applicable to producing small bubbles in liquid steel. Water modeling was carried out to investigate the impact of the free-fall length on gas entrainment by a short plunging jet. The results show that gas can be entrained into the liquid bath with a free fall longer than 15 mm. Part of the entrained gas is separated from the gas sheath by the rough surface of the inflow stream, forming initial bubbles. These initial bubbles are further refined into small ones of 0.4~2.5 mm due to the turbulent flow in the pouring region. The cylindrical shield can effectively isolate the surface fluctuation caused by the short plunging jet; thereby, a stable slag layer in the tundish can be maintained during gas entrainment.