Article ID: ISIJINT-2019-107
In this study, Al deoxidation experiments have been performed in a mildly stirred steel bath with controlled O and S concentrations, to investigate the effects of interfacial active elements on the agglomeration and removal of Al2O3 inclusions in molten steel. The decrease rate constants of total Al2O3 inclusions, Al2O3 cluster inclusions, and Al2O3 single inclusions as well as the maximum average diameter of Al2O3 cluster inclusions decrease with increasing O and S concentrations in molten steel. However, the effect of O is much greater than that of S. These experimental results have been analyzed based on the kinetics of Al2O3 inclusion removal and the interfacial chemical interaction between Al2O3 inclusions in molten steel. The following findings have been obtained on the agglomeration and removal mechanisms of Al2O3 inclusions in molten steel. The Al2O3 inclusions in molten steel are removed by a mechanism whereby large Al2O3 cluster inclusions, formed by Al deoxidation, float and separate while repeatedly agglomerating and coalescing with fine Al2O3 single inclusions suspended in molten steel. The agglomeration of Al2O3 inclusions during floating and separation can also be explained by a mechanism whereby the agglomeration force due to the cavity bridge force is exerted between the Al2O3 inclusions and the Al2O3 inclusions come in complete contact when the Al2O3 inclusions with thermodynamically agglomerating tendency are approaching each other. The effects of O and S interfacial active elements are considered in both these mechanisms.