What is it about?
his study investigates the hydrogen-induced cracking (HIC) of a thermomechanical controlled processed (TMCP) API 5L X65 steel pipe fabricated using the JCOE forming process. Despite passing HIC testing as a plate, the final pipe exhibited unexpected failure, highlighting the critical influence of pipe fabrication on material performance. The findings revealed that welding played a detrimental role, as all the HIC failures occurred at the welded area (0° orientation) due to welding-induced stresses and potential microstructural changes.
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Why is it important?
The effect of heat treatment on the grain size, residual stress, and susceptibility to HIC was investigated. It is believed that the welding process imposed reversible hydrogen traps in the HIC resistance plate ultimately reducing the HIC resistance. The heat treatment proved an effective method for relieving the applied micro-residual stresses that resulted in enhanced HIC resistance of the material.
Perspectives
While the steel plate demonstrated HIC resistance, the final pipe exhibited HIC failure, highlighting the critical influence of pipe fabrication on material performance. The applied stress-relieving heat treatment mitigated HIC susceptibility, as evidenced by the significant improvement in HIC resistance observed in heat-treated specimens. Stress-relieving heat treatment played a crucial role in the relaxation of the residual stresses and led to an improved HIC resistance of the steel.
Professor Milos B. Djukic
University of Belgrade, Faculty of Mechanical Engineering
Read the Original
This page is a summary of: Hydrogen-induced cracking of longitudinally submerged arc welded HSLA API 5L X65 carbon steel pipeline, Engineering Failure Analysis, September 2024, Elsevier,
DOI: 10.1016/j.engfailanal.2024.108561.
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