Abstract: The effect of cooling conditions on the corner transverse cracks of slabs with different section dimensions was studied by nozzle performance measurements, remehing and solidification cooling experiments and numerical simulations. The results show that the corner temperature is lower than the A₃ temperature earlier for slabs with section dimensions of 1000, 1160 and 1250 mm during a stronger cooling. There is a large number of film-like proeutectoid ferrite along grain boundaries, and transverse cracks form along prior austenite grain boundaries when straightening. To prevent from these transverse cracks, a process to control the surfaee mierostrueture of a slab was adopted and applied to actual production at Pansteel.