Effect of defect contained within weld metal on susceptibility of hydrogen embrittlement of carbon steel weld joint, 2

Kobayashi, Masato*; Takahashi, Rieko*; Asano, Hidekazu*; Taniguchi, Naoki ; Fujita, Tomoo 

Susceptibility of hydrogen embrittlement of carbon steel weld joint was evaluated by slow strain rate testing (SSRT) in consideration of a diffusive hydrogen concentration and a presence of a fine flaw which is hard to detect by ultrasonic testing due to the dimension. In order to avoid an effect of metallurgical micro structure, normalized specimens were prepared to the SSRT. The results of SSRT showed the rupture elongation decreases with an increase in hydrogen concentration. And observation of the fracture surface and measurement of the hydrogen concentration in the specimens showed a generation of a crack initiated from fine flaw at up to a certain value of hydrogen concentration. Although decreasing of fracture strain was observed on the specimens fracture morphology, it was evaluated as no significant effect in comparison with the effect of the concentration of the diffusive hydrogen in the specimens. These results suggest that a presence of a fine flaw has a small impact on the hydrogen embrittlement of weld joint.