SCM435鋼陰極水素チャージ試験片のSSRTによる水素脆性評価

（試験片直径の諸特性に及ぼす影響）

抄録

As an alternative method to evaluation of slow strain rate technique (SSRT) under high-pressure hydrogen gas, SSRT performed with a cathodically charged specimen. Cathodic charging was performed in 3% NaCl solution and at a current density of 400 A/m². Cr-Mo low alloy steel with a tensile strength of 1000 MPa grade was selected as a test material. The effect of specimen size on the hydrogen embrittlement properties was evaluated. Fracture surface observations ware performed using scanning electron microscopy (SEM). The inner region of hydrogen charged specimen covered with dimple fracture surface. In contrast, voids not observed near the outer, and quasi-cleavage confirmed. The smaller the specimen diameter, the larger the quasi-cleavage fracture rate, and the RRA decreased. The results indicated that the diameter of specimen influence the decreased in RRA.