高圧水素が低合金鋼の延性に及ぼす影響の簡易評価手法

―マスキングSSRTの試験条件の検討

抄録

The fracture surface obtained by concurrent cathodic hydrogen charging SSRT differs from that obtained by the high-pressure hydrogen gas SSRT, such that the fracture surface consists of multiple of surface-cracks. In this experiment, it was considered that the multiple surface cracks were caused by the large specimen surface where hydrogen penetrates. Masking SSRT condition was investigated to simulate SSRT in high-pressure hydrogen gas. Masking SSRT is concurrent cathodic hydrogen charging SSRT that limits the specimen surface of hydrogen penetration by masking. The hydrogen penetration width, i.e., the width at which the specimen is exposed to the solution and penetrated hydrogen, was clarified based on the hydrogen diffusion analysis when masking SSRT is conducted. The hydrogen contents of the hydrogen penetration width of 10 mm and that of without masking were equivalent after 4 hours, which is the time required for the concurrent cathodic hydrogen charging SSRT. Masking SSRT was conducted using SCM435 steel with hydrogen penetration widths of 10 mm and 5 mm. The breaking elongation of masking SSRT was slightly higher than that of without masking SSRT, but the stress behavior and RRA of masking SSRT were almost equivalent to those of without masking SSRT. The diffusible hydrogen contents obtained by masking SSRT and that of without masking SSRT were equivalent.