ばねの遅れ破壊に関する研究委員会報告その１ —CSRTとねじり試験による遅れ破壊評価法の検討—

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.

Delayed fracture, Hydrogen cracking, Diffusible hydrogen, Conventional strain rate technique, Torsion, Spring steel, SAE9254