Separation and dissolution of Al2O3 inclusions at slag/metal interfaces

To achieve better process control and product quality in clean steel manufacturing, it is necessary to understand the underlying processes behind (i) separation of inclusions across slag/metal interfaces and (ii) dissolution of the inclusions in the slag. This paper presents results on both these processes obtained through in situ observations with a confocal scanning laser microscope (CSLM) at steelmaking temperatures. In the case of inclusion separation, it was found that liquid inclusions could be observed to separate across the slag/metal interface and dissolve. Solid Al2O3 inclusions, however, were observed at the slag side of the interface and could be seen to agglomerate. The dissolution rate of slag particles was found to be a function of slag chemistry and temperature and to be controlled by diffusion in the liquid slag.