Relevance of hot ductility tests to crack sensitivity during continuous casting of steel

Hot tensile tests are performed on a Ni-alloyed steel after solution treating and cooling to test temperatures ranging between 600 and 950°C at strain rates of 3·10^-4 and 3·10^-3/s. The critical reduction of area (RA) for damage formation is determined by means of laboratory X-ray computed tomography. The results are compared with the corresponding RA at fracture traditionally used for assessing hot ductility and crack sensitivity during straightening of the slab. We demonstrate that using RA at fracture is inadequate for evaluating hot ductility in the austenite phase region at temperatures varying with the strain rate. Hot ductility curves more relevant for slow strain rate deformation are determined.