Abstract
Effect of nitrogen content has been investigated on hydrogen embrittlement of cold-rolled SUS 304 with the content 0.05%, 0.13% and 0.18%. The bend-test was employed for evaluating the hydrogen embrittlement and the number of bendings before failure was measured for H-free and H-changed specimens (N: H-free, NH: H-charged). The main results are as follows:
(1) For specimens whose Vickers hardness was below HV400, the number of bendings before failure of H-charged specimens (NH) increased with increasing nitrogen content. This effect of nitrogen content was not observed in specimens with HV>400.
(2) The ratio of hydrogen embrittlement [RH=(N-NH)/N] increased with increasing Vickers hardness. For specimens whose Vickers hardness was below HV400, the effect of nitrogen content was observed on the hydrogen embrittlement. The RH of 0.05%-N and 0.13%-N specimens were the same and were greater than the RH of specimens containing 0.18%N. For specimens whose Vickers hardness was in the vicinity of HV400, the RH of all kind of specimens were almost the same.
(3) Factors of the hydrogen embrittlement were strain-induced α' and ε martensite. The ratio of hydrogen embrittlement increased with increasing α' and ε martensite. For specimens whose α' martensite content was less than 35%, the influence of ε martensite content was observed on the hydrogen embrittlement.
