Large-scale transportation of hydrogen is an essential component to achieve the strategic goal of carbon peak and car-bon neutrality.However,blending hydrogen into the present natural gas pipeline network may cause hydrogen embrittlement of pipelines.Serious stress concentration at the weld joint may happen,which is prone to hydrogen enrichment and subsequent po-tential pipe failure.The two-dimensional model of steel 20 girth weld with inclusions was built by using the software of ABAQUS.The thermal-mechanical coupling method was used to analyze the welding temperature and residual stress fields.Subsequently,hydrogen diffusion simulations were conducted considering the microstructure heterogeneity of the welded joint and the presence of residual stresses at the weld seam,and the effect of the inclusion̍s distribution,orientation and㉼ shape on the hydrogen diffusion behavior in the weld seam was analyzed.The results show that,when the inclusions are parallel to the hydrogen diffusion orientation,the region of stress concentration around the inclusion̍s boundary is prone to hydrogen partial gathering.The maximum local hydrogen concentration at the inclusions-weld interface in the filler layer is about 2.45 times that of the root weld layer.When the inclusions are perpendicular to the hydrogen diffusion direction,the residual compressive stress is not favorable for hydrogen trapping in the stacked inclusions.The maximum hydrogen concentration in the filled layer was reduced by almost 48% compared to the inclusions parallel to the hydrogen diffusion direction.In addition,when spherical inclusions exist in the filler layer,there is no hydrogen enrichment at the inclusions-weld interface,and hydrogen diffuses into the pipeline steel area near the joint,increasing the risk of pipe failure.
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