Effect of Oxygen and Sulfur in Molten Steel on the Agglomeration Property of Alumina Inclusions in Molten Steel

The agglomeration force that acts between alumina cylinders in molten steel has been measured at different concentrations of oxygen and sulfur. Both oxygen and sulfur in molten steel reduce the agglomeration force between the alumina cylinders in molten steel and act as interfacial active elements. However, oxygen reduces the agglomeration force more significantly than sulfur. The agglomeration force that was obtained empirically has been analyzed by combining the formulated surface tension concerning molten steel containing oxygen and sulfur with a model representing the alumina interparticle interaction due to a cavity bridge force. Thus, this analysis enables the effect of oxygen and sulfur in the molten steel on the agglomeration property of the alumina inclusions in the molten steel to be evaluated. The agglomeration property of the alumina inclusions reduces with the increase in the concentration of oxygen and sulfur in molten steel. The reduction due to oxygen is much greater than that due to sulfur. Moreover, when the concentration of sulfur in molten steel increases, the alumina inclusions remain in an adhesion state due to the strong agglomeration force based on the cavity bridge force. However, because the agglomeration force markedly decreases when the concentration of oxygen in the molten steel increases, the alumina inclusions that have agglomerated once are likely to separate again due to the molten steel flow.