Abstract: In order to decrease and prevent the occurrence of slab transverse corner crack, effect of secondary cooling pattern on slab corner subsurface microstructure and related surface corner transverse crack was investigated via casing of P510L steel using a slab arc continuous caster. It is shown that, under the mild cooling pattern, the formation of continuous matrix was separated by the film-like ferrite along the prior austenite grain boundary, which decreased the hot ductility of slab subsurface; under the control cooling pattern, the microstructure was even and film-like ferrite was inhibited in the range of 2-3mm to the slab surface, resulting in promoting the reduction of transversal cracking susceptibility. And compared to the mild cooling pattern, under the optimized cooling pattern, the crack index fell from 3.2 down to 0.4.

Key words: continuous casting, micro-alloyed steel, microstructure, surface transverse cracks