Liquid Steel Refining in the Ladle with Non-Oxidising Synthetic Slag

The steel-refining method by Ar-gas bubbling into liquid steel from the bottom of the ladle has been reported. But under the existence of normal slag containing much FeO in the ladle, so much effect can not be expected because of reoxidation of liquid steel by the slag.Two kinds of nonoxidising synthetic slags were made and applied to low C-Al killed steel. After the complete slag-off from the furnace, heats were tapped and synthetic slag (s-slag) was added into the ladle under the condition of Ar-bubbling.The effect of kinds of s-slags and lining-materials was studied and the following results were found.1) If the FeO content of slag in the ladle reduced under 2%, liquid steel was purified and total oxygen reached less than 40 ppm. Large inclusions (≥100μ) were also eliminated.2) Loss of sol. Al in liquid steel was caused not only by slag but also by lining material. Relative contribution of lining-material to sol. Al loss became higher by the case of s-slag treatment than by normalslag. It can be suppressed, however, by using high Al2O3 content lining-material.3) The velocity of sol. Al loss was controlled by diffusion of oxygen in slag.