Article: Hot ductility and fracture mechanisms of a C-Mn-Nb-AI steel

Hot-ductility tests of a C-Mn-Nb-Al steel were performed in a tensile machine at different strain rates of 1 x 10-4, 3 X 10-4, 1 X 10-3, and 3 X 10-3 s-1 and at temperatures of 650 deg C, 710 deg C, 770 deg C, 840 deg C, 900 deg C, 960 deg C, and 1020 deg C, which are close to the continuous casting conditions of steel. Fracture surfaces were examined using a scanning electron microscope. It was found that low strain rates and coarse austenitic grains decrease hot ductility. At all test temperatures, when the strain rate decreases, the hot ductility also decreases because the void growth mechanism predominates over void nucleation, giving time for nucleated cracks to grow. This leads, ...