Formation of Phosphorous Surface Inverse Segregation in Twin-Roll Cast Strips of Low-Carbon Steels

The formation of phosphorous surface inverse segregation （SIS） in twin-roll cast strips of low-carbon steels was studied. High phosphorous strips were fabricated by using a pilot twin-roll strip caster and a melt/substrate contacting apparatus, respectively. Solidification structures of strips were observed and analyzed, and phosphorus distributions along longitudinal sections of strips were investigated and discussed. The results showed that solidification structures of all strips were columnar grains, either integrated or coarse in the strip made by the melt/substrate contacting apparatus or damaged in some degree in cast strips; and that during cast strip solidification, enrichment of phosphorus occurred between columnar grains, and the average phosphorus concentration near the surface in the strip with 0.15% of phosphorus was measured to be about 0.27% which was obviously higher than that in the bulk.