Stress Oriented Hydrogen Induced Cracking (SOHIC) is a type of environmental cracking under wet H2S conditions, with distinctive ladder-like internal cracking. Previous SOHIC studies have indicated that tri-axial stress conditions were needed to generate SOHIC. Stress conditions, however, are difficult to simulate using simple tensile and bending methods. A standard small-scale test method for evaluating SOHIC susceptibility has not yet been clearly identified, though some SOHIC evaluation methods have been proposed.

In this study, which examines a small-scale SOHIC evaluation method, the effect of applied stress conditions and steel microstructure on SOHIC susceptibility was investigated using a twist-bend method. The test method involves applying a small level of twist and flexural stress simultaneously, to change applied stress conditions. UNS(1) K03014 sour grade carbon steel plates for manufacturing welded linepipes were used in this study, with several heat treatments applied to simulate welded portions. Results showed that low strength ferrite-pearlite micro-structural portions are susceptible to micro Hydrogen Induced Cracking (hydrogen blistering), and that micro HIC propagation behavior strongly depends on the applied external stress. Especially noticeable was the fact that, under high tensile stress parallel to the micro HIC, micro HIC propagation behavior showed ladder-like internal cracking.

Subject
Hydrogen induced cracking, Test methods, Materials, Rolling, Stress cracking, Stress, Tensile stress, Stress oriented hydrogen induced cracking, Hydrophobic interaction chromatography, Ferrite, Blistering, Hardness, Hydrogen
Keywords:
SOHIC, HIC, Hydrogen blistering
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2014
Association for Materials Protection and Performance (AMPP)
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