Abstract:The causes of intermediate crack generated in the Tonggang FTSC thin-slab of SS400 whose cross-section is 1250×72 were analyzed. The defects ratio of SS400 was effectively controlled by optimization of reduction end point of the segment, the rolling reduction of the segment entry and export, the secondary cooling water; changing the segments with rollers which do not rotate on time and removing scale between segment rollers to decrease torsion of pinch rolls.