連続陰極水素チャージSSRT試験における低合金鋼の破壊挙動

抄録

In order to reduce the construction cost of hydrogen infrastructure facilities, application of inexpensive materials such as low alloy steel is required. However, when hydrogen embrittlement is a concern, as in the case of low alloy steels, acquisition of material data in high-pressure hydrogen gas and proof of safety are necessary for application. Since the testing in high-pressure hydrogen gas incurs a high cost as a simple evaluation technique for the mechanical properties of materials in high-pressure hydrogen gas. While the comparison of mechanical properties such as total elongation in these two test environments has been an object of research, the difference in fracture processes is still not clear. In this study, slow strain rate tensile (SSRT) tests in high-pressure hydrogen gas and cathodic charge were conducted with two materials that had been controlled to different strengths by heat treatment, and their fracture behavior was investigated. Regardless the fracture mechanisms attributed to material strength, such as quasi-cleavage and intergranular-like fracture, the cathodic hydrogen charging SSRT test showed fracture displacement and a reduction of area equivalent to those in high-pressure hydrogen gas. However, the nominal stress-displacement curves showed different behavior immediately before final fracture. A detailed examination of the fracture processes of the specimens revealed that the difference in the fracture behavior of the specimens in the high-pressure gas test and in the cathodic hydrogen charging test was caused by the difference in hydrogen-induced crack growth behavior.