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 sin2Ψ 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.
Highlights
High-strength low-alloy (HSLA) steels are widely used in the production of pipes for the oil and gas industry due to their mechanical properties of high strength, good toughness, and excellent weldability[1,2]
This paper presents a study of the effect of hydrogenation on the residual stresses and mechanical behavior of an API 5L X65 steel, in the as-received and welded by electric resistance welding (ERW) process conditions
The microstructure of the fusion zone presents a scattering of grain size, but even with this fact the average size is slightly higher than base metal (BM) and heat affected zone (HAZ)
Summary
High-strength low-alloy (HSLA) steels are widely used in the production of pipes for the oil and gas industry due to their mechanical properties of high strength, good toughness, and excellent weldability[1,2]. The electric resistance welding (ERW) manufacturing process of API 5L X65 steel pipes led to an increase in mechanical strength and toughness of the weld region, even in conditions of low temperature and in the presence of H2S gas[3]. The failure of steel pipes used in the oil industry is mainly caused by hydrogen effects or stress corrosion cracking. Hydrogen damage occurs because the inner walls of the steel pipes can be in permanent contact with hydrogen sulfide gas generated during the petroleum oil process. This paper presents a study of the effect of hydrogenation on the residual stresses and mechanical behavior of an API 5L X65 steel, in the as-received and welded by ERW process conditions. The synthetic solution NS4 mimics the soil corrosivity used as a hydrogen source to metallic specimens under cathodic polarization
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