高強度鋼の遅れ破壊に及ぼすショットピーニングの効果

抄録

A study was made on the effect of shot peening on delayed fracture of high strength steel at a level of 1300MPa and 1400MPa. To investigate this effect, three types shots, having different hardness and mean diameter, were prepared to make the different residual stress distribution in the bending type specimen. Using these shots, specimens were peeved by an air type shot peening device. It was confirmed that the delayed fracture resistance of each shot peened specimen was improved compared with those of as quenched and tempered specimens due to an increase in compressive residual stress. By measuring the displacement of moment arm, it was found that this result was caused mainly by a prolonged incubation period to crack initiation, the reason of which would be that the compressive residual stress defended hydrogen entry in metal.