抄録
Influences of tensile strength, hydrogen concentration and applying stress mode (tension or torsion) on delayed fracture properties have been investigated using SAE9254 steel treated in their tensile strength range of 1700-2000MPa. In conventional strain rate techniques (CSRT), the delayed fracture strength tends to decrease with the increment of diffusible hydrogen concentration, especially less than 1 mass ppm. On the other hand, in torsional tests, the hydrogen cracking susceptibility shows less abrupt change than in CSRT, while the fracture torque decreases and intergranular cracks are observed in the notch root of specimen when hydrogen is charged above 10 mass ppm.
