| Summary: | In order to clarify the effect of hydrogen-gas pressure on threshold of hydrogen-induced crack growth (KI,H), elasto-plastic fracture toughness tests were performed on JIS-SM490B carbon steel, JIS-SCM435 low-alloy steel and JIS-SUS304 stainless steel. For JIS-SM490B and JIS-SUS304, the values of KI,H at displacement rates of 2×10–5 and 2×10–4 mm/s were almost the same in hydrogen at pressures of pH2= 20, 45 and 115 MPa (KI,H ≒ 80 MPa·m1/2 for JIS-SM490B and 150 MPa·m1/2 for JIS-SUS304). In contrast, for JIS-SCM435, the values of KI,H at displacement rates of 2×10–5 and 2×10–4 mm/s were the same in hydrogen gas at pressures of pH2 = 20, 45 and 80 MPa (KI,H ≒ 100 MPa·m1/2); however, those of KI,H were degraded in 115-MPa hydrogen gas (KI,H ≒ 50 MPa·m1/2). Based on the HISCG (Hydrogen Induced Successive Crack Growth) model, an effect of pH2 on KI,H and an existence of KI,H were also discussed for JIS-SM490B, JIS-SCM435 and JIS-SUS304.
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