渗氢X70管线钢焊接接头的力学性能及缺口敏感性

Mechanical Properties and Notch Sensitivities of the Hydrogenated X70 Pipeline Steel Welded Joints

为探究管道内壁表面缺陷对长期输送掺氢天然气(HCNG)管线钢焊接接头的可靠性的影响,在X70管线钢焊接接头的母材、焊缝及热影响区处开缺口,并对缺口部位进行电解渗氢,开展有、无渗氢X70管线钢焊接接头缺口试样拉伸力学性能、显微组织及其缺口敏感性的测试分析。结果表明:渗氢导致X70管线钢焊接接头试样的拉伸力学性能,尤其是塑性(断后延伸率A)的降低。由于缺口与氢损伤的叠加效应,缺口处组织未发生明显变形,拉伸断口呈准解理断裂特征。有、无渗氢X70管线钢焊接接头均具有一定的缺口敏感性,渗氢致使焊接接头的缺口敏感性增大,渗氢焊缝的缺口敏感性较大,在管道检修时应予以关注。

In order to explore the effects of pipeline inner-wall surface defects on reliability of the hydrogen enriched compressed natural gas(HCNG)pipeline steel welded joints in long-term service,the notches in the base metal,weld seam and heat affected zone of X70 pipeline steel welded joints were made,and the electrolytic hydrogen permeation on the notches was performed.Tests and analysis of the tensile mechan-ical properties,microstructures and notch sensitivities of the X70 pipeline steel welded joint notch samples with/without hydrogen permeation were carried out.Results showed that hydrogen permeation led to a decrease in the tensile mechanical properties of X70 pipeline steel welded joint samples,especially plasticity(elongation at break A).Due to the combined effect of notch and hydrogen damage,the tissue at the notch did not undergo significant deformation,and the tensile fracture exhibited quasi cleavage fracture characteristics.Furthermore,the welded joints of X70 pipeline steel with and without hydrogen permeation had certain notch sensitivity,and hydrogen permeation could increase the notch sensitivity of the welded joint.Therefore,the hydrogenated welding seams should be paid more attention during the pipeline maintenance,be-cause of their higher notch sensitivity.