The tearing resistance dJ/da of three kinds of 2.25Cr-1Mo steels and 2.25Cr-1Mo-0.3V steel with internal hydrogen was measured using the potential drop method. Internal hydrogen refers to test specimens that are precharged (thermally charged) prior to testing. In general, Cr-Mo steels used widely in the refining and petrochemical industry are susceptible to temper embrittlement. However, there are very few studies concerning the effects of hydrogen and temper embrittlement on J-resistance properties. The test specimens were prepared by subjecting them to normalizing, tempering and post-weld heat treatments which simulated actual conditions. Some specimens were embrittled by step cooling (Socal-1 treatment). Hydrogen substantially reduces the dJ/da of the steels other than the V-bearing steel and temper embrittlement additionally causes adverse effects on the dJ/da of the steels with internal hydrogen where the temper embrittlement parameter J-factor is larger than around 300.

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