FRACTURE OF HOT FORMED LEDEBURITIC CHROMIUM STEELS

Due to the hot forming procedure the overall mechanical properties of ledeburitic chromium steels become anisotropic. As shown by experiment s the fracture toughness K-Ic of these steels depends on the hardness of the metal matrix and the orientation of the load with respect to th e axis of hot forming. The degree of crack deflection, expressed by th e width of the crack path, was found to be the governing quantity for differences in the resistance against crack propagation. The K-Ic-test s were modelled by the finite element method using an orthotropic elas to-plastic material law. While the behaviour of the hardened and low t empered specimens could be well predicted by this model, differences b etween simulation and experiment in the case of a ductile state indica te the occurrence of additional effects acting on a microscopical scal e. (C) 1997 Elsevier Science Ltd.