In-situ Observation on the Formation and Aggregation of Al₂O₃ Inclusions in Molten Steel

The formation of Al₂O₃ inclusions,aggregation and movement of Al₂O₃ clusters to solid-liquid interface are observed by high temperature laser confocal microscopy.It is found outthat it takes only 1.5 s to form Al₂O₃ granulates and the Al₂O₃ granulates far from 145 μm apart gather into a 78 μm cluster spontaneously.It takes only 0.5 s for the aggregated Al₂O₃ cluster to be absorbed and moved from the suspension position in molten steel to the solid-liquid interface,the subsequently formed single Al₂O₃ particles are rapidly absorbed by the Al₂O₃ cluster,the Al₂O₃ cluster shrink to mass in 1 s.The theoretical analysis shows that the van der Waals force is the main force acting on the aggregation of Al₂O₃ inclusions and Al₂O₃ cluster adsorbed by solid-liquid interface,and the larger the size of inclusions.Greater the van der Waals force,results in faster movement of inclusions.The spontaneous shrinkage of Al₂O₃ clusters is mainly caused by the liquid bridge force.