A low-blow Charpy technique was used to study the response of the notch-tip region to impact in X52, X60, X65, and Xl OO* steels. Both carbide and inclusion microcracks are formed, with the latter being longer and associated with lower toughness. Considering carbide microcracks only, spheroidite is found to be a tougher constituent than pearlite. In addition, the spheroidized structure tends to disperse slip bands. Both of these effects cause the reported improvements in ductility due to spheroidization, which in turn is related to the Charpy shelf energy. A relation between Charpy shelf energy...
A low-blow Charpy technique was used to study the response of the notch-tip region to impact in X52, X60, X65, and Xl OO* steels. Both carbide and inclusion microcracks are formed, with the latter being longer and associated with lower toughness. Considering carbide microcracks only, spheroidite is found to be a tougher constituent than pearlite. In addition, the spheroidized structure tends to disperse slip bands. Both of these effects cause the reported improvements in ductility due to spheroidization, which in turn is related to the Charpy shelf energy. A relation between Charpy shelf energy and unnotched tensile properties is rationalized in terms of the effect of constraint on ductility and the local notch-tip strain in a Charpy bar.