1996 Volume 36 Issue Suppl Pages S159-S162
Stress-strain data of continuously cast (CC) steel at high temperatures available in the past are based on uni-axial tensile tests in a uniform temperature field, the data being utilized for thermal stress analysis to simulate crack formation on a CC-slab surface. New equipment for hot tensile and bending tests has now been developed by the authors that allows determination of more realistic stress-strain behavior of the solidifying shell subjected to temperature gradients similar to those in a CC-mold. Key factors affecting crack formation have been studied with this equipment. Fine cracks were found to form at the hot side of the tensile test-piece during straining. These cracks are initiated at grain boundaries which are located on the previous interdendritic solute-segregated region. The critical strain for the crack formation is independent of the strain rate within the range of 5–50×10-4s-1, depending on the carbon content, measuring 2% for peritectic carbon steels, 1.5% for ultra low carbon steels and about 1% for low, middle and high carbon steels.