Abstract: In this article, various means were used to study the influence factors and control of transverse corner cracks on hypoperitectic steel slabs for improving the slab surface quaility. The microstructures implicated that proeutectoid ferrites along austenite grain boundaries could increase two times of the occurrence fraction of cracks. The carbon content makes an essential influence on the hot ductility of steel. Reduce carbon content to 0.07% could sharp reduce the cracks occurrence fraction from 44% to about 4% in the carbon cotent range less than 0.1%. A secondary cooling scheme of a weak cooling intensity before the bending segment and followed by an strong cooling intensity at the straightening segments was suggested and was proved to be effective in eliminating transverse corner cracks, both the cracks number and length were markly reduced.

Key words: cracks, proeutectoid ferrites, reduce carbon content, optimizing secondary cooling water amount