Based on the hot ductility curves at 600～1400 ℃ tested by Cleeble1500 thermal/strain simulation machine for 0.16~0.20C

0.020~0.060Al

t

Q235B steel 70 mm x 1500 mm thin slab produced by compact strip production (CSP)process

the third brittle zone of cast slab was between 700~900 ℃.Therefore the crack of cast slab easily forms as straightening in this temperature range. With fracture morphology analysis by scanning electron microscope and composition analysis by electron probe micro analyzer

it is obtained that the deformation-induced ferrite network precipitation and AlN precipitated at lower temperature austenitic range lead to cast slab embritlement.