"In-situ" observation of collision, agglomeration and cluster formation of alumina inclusion particles on steel melts

Abstract

A long-range strong attraction between alumina and alumina-rich solid inclusion particles, and detailed sequence of the collision, agglomeration and formation of alumina clusters have been observed first time "in-situ" on molten steel surface by using a confocal scanning laser microscope combined with an infrared image furnace. This attraction force has been found to be over 10-16 N, reach over 10 μm for alumina particles larger than 3 μm, and play an important role to promote collision between the particles to form intermediate aggregates, the same between the intermediate aggregates to form loose alumina clusters, and to densify the loose clusters into compact ones. The origin of this long-range strong attraction has been examined to be caused by capillary effect around alumina particles on molten steel surface. Interfacial phenomena at three-phase interface of inert gas-alumina-molten steel is also discussed. In industrial practice, the capillary attraction between the fine alumina inclusions can improve the collision, agglomeration and cluster formation at gas bubble/liquid steel interface when gas injection/bubbling is utilized for refining steels.