Prevention of transverse corner cracks in continuously cast steel slabs using asymmetric secondary cooling nozzle

Transverse corner cracks were observed frequently in Nb containing steel slabs produced by a vertical bending type slab caster. The hot ductility of the steel was measured with a hot tensile test, and the result indicated that the temperature at the slab corner fell into the embrittlement temperature range which resulted in the cracking problem. To ensure that the temperature of the slab was uniformly above the embrittlement temperature range during the straightening process, asymmetric secondary cooling nozzles have been implemented on the caster. After this modification, the temperature of the slab corner during the unbending operation was increased to above the embrittlement temperature range of the Nb bearing steel, and the incidence of transverse corner cracks was greatly reduced.