Katsuhiro Sasai
This study has analyzed the growth and removal mechanisms of Al2O3, MgO, MgAl2O4, ZrO2, SiO2, and Ti3O5 inclusions in molten steel formed through the addition of various deoxidizing elements by dividing them into single inclusions and cluster inclusions resulting from the agglomeration of these inclusions with a focus on kinetics. Additionally, we have evaluated the maximum particle diameter of cluster inclusions from both thermodynamic and agglomeration force perspectives to examine the agglomeration properties and mechanisms of various inclusions. The growth mechanism of various single inclusions, measuring several micrometers in diameter and suspended in molten steel, is governed by Ostwald ripening with collision agglomeration due to Brownian motion and turbulent stirring. Contrarily, cluster inclusions with diameters of 10 µm or more float in molten steel agglomerate with suspended single inclusions. Depending on the inclusion type, they also agglomerate with other clusters along their floating paths, growing larger and undergoing floating separation. Furthermore, the agglomeration strengths of various inclusions in molten steel follows the order MgO < Ti3O5, SiO2 < MgAl2O4 < ZrO2 < Al2O3. The kinetic mechanism of agglomeration growth is explained in a unified manner by the interparticle interactions of agglomeration force driven by cavity bridge forces.