Abstract��The thin strip-shaped and fine sand-shaped defects were usually observed during the ultra-low carbon steel produced in one hot rolling plant. These two types of typical defects were analyzed by EPMA�� SEM and EDS. The formation cause of two defects was comprehensively discussed by combining with the rolling process in site. The analysis results indicated that the oxidized round spots were not found near two types of defects. Both defects were formed during the rolling process. The thin strip-shaped defect was due to the enrichment of Mn in oxide scale. The interface between oxide scale and matrix was rough and uneven�� rendering the ��pinning�� effect of oxide scale. The deteriorated peeling property of oxide scale resulted in the residue during descaling. The residual primary scale was embedded and formed during the subsequent rolling process. The fine sand-shaped defect was due to the peeling of oxidation film from surfaces of F1-F3 work rolls�� causing the rough and uneven roll surface. It was rolled into the surface of strip steel during the subsequent rolling of stand. As a result�� the third oxide scale was embedded. The corresponding improvement measures for two types of defects were also proposed.
2016, Vol. 34 
