51314-3883-Study of Stress Oriented Hydrogen Induced Cracking Mechanism and the Evaluation Method

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Product Number: 51314-3883-SG

ISBN: 3883 2014 CP

Author: Kenji Kobayashi

Publication Date: 2014

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Stress Oriented Hydrogen Induced Cracking (SOHIC) is a kind of environmental cracking under wet H2S conditions and distinctive ladder-like internal cracking are observed. Previous studies about SOHIC indicated that tri-axial stress condition was needed to generate the SOHIC. The stress condition however is difficult to simulate by simple tensile and bend methods. A uniform small scale test method for evaluating the SOHIC susceptibility of material has not been clarified yet though some SOHIC evaluation methods has been already proposed.In this study for discussing a small scale SOHIC evaluation method a SOHIC mechanism was investigated by using a twist-bend method. The concept of test method is to apply a small level of twist and flexural stress simultaneously and the method can change the applied stress conditions. UNS K03014 sour grade carbon steel plates for manufacturing welded line pipes were used in this study by applying several heat treatments for simulating the welded portions. From the results low strength ferrite - pearlite microstructural portion has a susceptibility of micro Hydrogen Induced Cracking (hydrogen blistering) and the micro HIC propagation behavior strongly depended on the applied external stress. Especially under high tensile stress parallel to the micro HIC the micro HIC propagation behavior showed ladder-like internal cracking.