Revealing interfacial properties and agglomeration characteristic of rare earth aluminate inclusion in molten steel

Abstract

The formation of large, harmful rare earth (RE) inclusions in RE-containing steels is closely related to their agglomeration behavior, which is strongly influenced by the interfacial properties between inclusions and molten steel. To reveal the agglomeration characteristic and mechanism of RE-aluminate inclusions, this study first prepared the LaAlO₃ substrate and the steel sample containing only such inclusions. Based on that, the interfacial properties including that contact angle between inclusions and melt, surface tension of melt and interfacial energy between inclusions and melt were measured using the sessile drop method. Moreover, the agglomeration behavior of these inclusions was observed in situ by confocal laser scanning microscopy (CLSM). Thereafter, the theoretical models of agglomeration forces were used to quantitative analysis the agglomeration behavior of inclusions. The results show that LaAlO₃ inclusions are easier to agglomerate and form large-sized clusters. Compared with capillary force, cavity bridge force is the more important reason for inclusions agglomeration once the distance between them is close enough, and the contact angle between inclusions and molten steel plays a dominant role on affecting inclusions agglomeration. Similar to Al₂O₃, the strong agglomeration tendency of LaAlO₃ is attributed to their poor wettability with molten steel. This study can provide theoretical support for controlling RE-inclusions to improve the problems of nozzle clogging and product defects in RE-containing steels.