In this paper, the estimation expression of critical concentration for hydrogen-induced cracking and estimation expression of critical stress intensity factor KISCC for hydrogen-induced delayed brittle fracture of the three Chinese steels for pressure vessels — 16MnR, 15MnVR and 07MnCrMoVR in Chinese standard GB 6654 are derived first according to SCC mechanism and in combination with fracture mechanics techniques, and verified by comparison with test values. The estimation expressions of diffusion-dominated crack plateau growth rate da/dt of these three materials are derived using Gerberich model based on the analysis of dynamic control mechanism of hydrogen-induced crack propagation under wet H2S environment and the estimated values are verified with the test results for WOL specimens. And the effect of concentration limit and concentration of the medium at normal temperature on the dynamic control process of crack propagation is also discussed.

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