Influence of Hydrogenation on Residual Stresses of Pipeline Steel Welded Joints

Abstract

Hydrogen embrittlement is a phenomenon that affects the performance of steel used for oil and gas pipelines. This paper presents a study of the effect of hydrogenation on the residual stresses of an API 5L X65 steel pipe. Residual stresses were analyzed by X-ray diffraction technique using the sin 2 Ψ method. The hydrogenation of base metal and welded joint specimens was performed by electrochemical tests in a simulated soil solution NS4. Results show that the hydrogenation led to significant changes in residual stress configuration and in the mechanical properties of steel. The hydrogenation increased the magnitude of the longitudinal residual stress of base metal and fusion zone, without changing the tensile/compressive nature. On the other hand, the hydrogenation increased the intensity of the tangential stress of base metal, and changed from compressive to tensile the residual stress of the fusion zone. The microstructural characterization by optical and scanning electron microscopy was used to complement this study.

Effect of Residual Stress on Hydrogen Diffusion in Thick Butt-Welded High-Strength Steel Plates

“…Hydrogen can reduce the properties of materials and is often accompanied by hydrogen embrittlement (HE) [7,8]. The entry of hydrogen into materials is harmful in general, giving rise to issues such as microcracks caused by hydrogen pressure (or welding cold cracks), hydrogen-induced plastic loss, and hydrogen-assisted cracking (HAC) or fracture.…”

“…Gong [26] and Yan et al [27][28][29] measured the parameters related to hydrogen diffusion using the electrochemical penetration method and numerically simulated the variation of hydrogen concentration and residual stress in welded joints of 12 mm thick 16MnR steel and X80 pipeline steel. de Souza Sant'Anna et al [8] studied the influence of hydrotreatment on residual stress in an API 5L X65 steel pipe with a wall thickness of 9.5 mm using the electrochemical method. Although these studies investigated the influence of welding residual stress on hydrogen diffusion through a combination of numerical simulations and experiments, they focused only on thin shells or thin plates with low yield strength.…”