Analysis on Shell Defect at Edge of SPHD Hot-rolled Strip Steel

Shell was founded at the edge of SPHD hot-rolled strip steel. The reason of shell was analyzed by means of macro examination, chemical composition analysis, metallographic examination, SEM and energy spectrum analysis. The results showed that the main reason was slag entrapment defect of continuous casting billet. After deformation of roughing passes, the deformation in low temperature area at the corner of intermediate billet was beyond the tolerance thermoplastic of material under the action of vertical roll side pressure, and the corner cracks were produced, which couldn′t be welded in rolling process, then the continuous shell was produced along the rolling direction, and the shell was turned over to the top and bottom of slab in the flanging process of intermediate billet. In the end the shell was distributed in the edge area of hot-rolled strip.