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 experiments 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 the axis of hot forming. The degree of crack deflection, expressed by the width of the crack path, was found to be the governing quantity for differences in the resistance against crack propagation. The K-Ic-tests were modelled by the finite element method using an orthotropic elasto-plastic material law. While the behaviour of the hardened and low tempered specimens could be well predicted by this model, differences between simulation and experiment in the case of a ductile state indicate the occurrence of additional effects acting on a microscopical scale. (C) 1997 Elsevier Science Ltd.