To provide engineering data useful in the design, manufacture, and operation of seamless pressure vessels, extensive tests have been conducted in hydrogen at pressures ranging from 3000 to 14,000 psi (21–97 MN/m2) with precracked specimens of steels having a wide range of mechanical properties. The critical stress-intensity level at which crack propagation spontaneously arrests, KH, was determined. The values of KH were used in an illustrative calculation to estimate the critical flaw size at which hydrogen crack propagation would be expected in thick members loaded in bending. In general, the susceptibility of steels tested increased with yield strength. For the steels with intermediate yield strengths (85–113 ksi or 586–779 MN/m2), KH tended to decrease as pressure was increased from 3000 to 14,000 psi (21–97 MN/m2). The crack path was analyzed, and a sequence of events is described involving the initiation, growth, and arrest of cracking induced by gaseous hydrogen.

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