Causes Analysis on Center Cavities and Edge Cracks Defects of Q235B Steel Hot Rolling Plate

The formation causes of center cavities and edge cracks defects of Q235B steel hot rolling plate produced in an iron and steel company were analyzed by means of macro analysis, chemical compositions analysis, metallographic examination, energy spectrum analysis and so on. The results show that the center cavities and edge cracks defects were caused by the abnormal continuous casting which resulted in formation of surface pores at edge and serious sulphur segregation at center of the continuous casting slab. The serious sulphur segregation resulted in the formation of plenty of banded sulfide inclusions including low melting FeS, which led to the formation of center cavities defect during the hot rolling process. The surface pores at edge of the continuous casting slab led to the formation of edge cracks defect during the hot rolling process.