IN-SITU OBSERVATION OF COLLISION, AGGLOMERATION AND CLUSTER FORMATIONOF ALUMINA INCLUSION PARTICLES ON STEEL MELTS

A long-range strong attraction between alumina and alumina-rich solid inclusion particles, and detailed sequence of the collision, agglomera tion 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 fo rce has been found to be over 10(-16) N, reach over 10 mu m for alumin a particles larger than 3 mu m, and play an important role to promote collision between the particles to form intermediate aggregates, the s ame between the intermediate aggregates to form loose alumina clusters , and to densify the loose clusters into compact ones. The origin of t his long-range strong attraction has been examined to be caused by cap illary effect around alumina particles on molten steel surface. interf acial phenomena at three-phase interface of inert gas-alumina-molten s teel is also discussed. In industrial practice, the capillary attracti on between The fine alumina inclusions can improve the collision, aggl omeration and cluster formation at gas bubble/liquid steel interface w hen gas injection/bubbling is utilized for refining steels.