Tearing Resistance Properties of Cr-Mo Steels with Internal Hydrogen Determined by the Potential Drop Method

The tearing resistance, dJ/da, of conventional 2.25Cr-1Mo steels and a V-bearing steel (2.25Cr-1Mo-0.3V steel) with internal hydrogen was measured using the effective offset 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 industries, are susceptible to temper embrittlement. However, very few studies have dealt with the effects of hydrogen and temper embrittlement on the tearing resistance. Test specimens were prepared by subjecting them to normalizing, tempering, and post-weld heat treatments that simulated actual conditions. Some specimens were embrittled by step cooling. Hydrogen substantially reduced dJ/da for all samples except for that for the V-bearing steel, and temper embrittlement caused additional adverse effects on dJ/da for samples with internal hydrogen for which the temper embrittlement parameter, i.e., the J-factor, was large.