Effect of interfacial properties on the characteristics and clustering of alumina inclusions in molten iron

For the purpose of controlling the size of non-metallic inclusions in steel, the effect of interfacial properties of alumina inclusions and molten iron on the characteristics and clustering of alumina inclusions was investigated. The interfacial properties were modified by adding different amounts of Te to molten iron at 1 873 K before Al deoxidization. When the melt is not stirred after Al addition, Te was found to decrease the size of alumina inclusions and to narrow the size distribution by promoting nucleation. This effect, however, fades out with increasing holding time. When the melt is stirred for 30 s after Al addition, Te favors alumina clustering. The mean diameter of alumina inclusions, the clustering degree and the average number of particles per cluster increase with increasing Te addition from 0 to 250 ppm, thereafter decrease with further Te addition. The effect of Te addition on the clustering of alumina inclusions is discussed from the viewpoint that Te makes alumina inclusions more faceted and Te decreases the surface tension of molten iron.