Assessing girth weld quality of pipeline steels and their susceptibility to hydrogen embrittlement

Published

August 28, 2024

Author(s)

Zack Buck, Newell Moser, Nicholas Derimow, May Ling Martin, Damian Lauria, Enrico Lucon, Douglas Stalheim, Peter Bradley, Matthew Connolly

Abstract

Hydrogen has long been considered a viable carbon-free option for ever-increasing societal desires to transform our energy infrastructure towards more renewable and alternative technologies. However, the effects of hydrogen-assisted damage mechanisms that result in the embrittlement of metals, particularly ferritic steels, continues to be a persistent obstacle in designing and manufacturing reliable structural materials for use in energy storage and transportation applications. Conventional ferritic steel pipelines used to transport natural gas are susceptible to embrittlement and subsequent structural failure due to fatigue, reduction in ductility, and fracture when exposed to hydrogen. Predicting lifetimes of pipelines can be difficult due to many variables including geography (terranean vs offshore), the type of gas being transported, and the welding processes involved in the manufacturing and joining of steel pipelines in the field, which can produce a variety of chemistry and microstructures. To ensure safe operation of pipelines for hydrogen and/or blended gas mixtures, it is critical to assess the weld qualification requirements when considering new pipeline materials and weld processes. The National Institute of Standards and Technology (NIST) is currently conducting a multi-year study, sponsored by the U.S. Department of Transportation, to investigate the quality of steel pipelines that contain seam and girth welds spanning a diverse range of microstructures and grades. A thorough investigation of the mechanical properties of 10 pipes, investigating baseline steel, the heat-affected zones, and their welds, has produced a large data set of material properties. Over one hundred ASTM E1820 fracture toughness tests have been performed in air, and in 20.6 MPa high-purity hydrogen and blended hydrogen/methane environments to charactierize the quality of the different welds. Additionally, optical microscopy, Charpy testing, and hardness mapping all contributed to this data set and provided insight into the performance of these welds. Lastly, Principal Component Analysis (PCA) is being applied to this large data set to help identify correlations between material properties that will aid in the classification of these welds for use in hydrogen service and prediction of their lifetimes. The ultimate goal of these tests and PCA is to classify base metal and weld microstructures based on their suitability for hydrogen service, in order to provide recommended microstructures to industry worldwide.

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Talks

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Citation

Buck, Z. , Moser, N. , Derimow, N. , Martin, M. , Lauria, D. , Lucon, E. , Stalheim, D. , Bradley, P. and Connolly, M. (2024), Assessing girth weld quality of pipeline steels and their susceptibility to hydrogen embrittlement, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958330 (Accessed October 6, 2024)