Experiment on hydrogen embrittlement sensitivity of L245 pipeline steel girth weld with different stress concentration factors
The welding of pipe girth weld will cause the change of microstructure and mechanical property,and it usually inevitably leads to welding imperfection.Hydrogen atoms can be aggregated in the region of stress concentration formed by welding imperfection,which will enhance the hydrogen embrittlement sen-sitivity of material.In this study,L245 hydrogen transport pipeline steel was selected.The girth weld notch tension samples were tested at slow strain rate under 6.3 MPa hydrogen and nitrogen environments.The hydrogen embrittlement sensitivity change law of weld metal with different stress concentration fac-tors was investigated.Moreover,the microstructure of fracture was characterized and analyzed by scanning electron microscope(SEM).The results showed that the hydrogen embrittlement sensitivity of weld metal did not monotonically increase with the increase of stress concentration factor.When the stress concentra-tion factor increased to a certain value,the hydrogen embrittlement sensitivity decreased instead.The con-cept of transition stress concentration factor(Ktt)based on the tests was proposed.The critical stress con-centration factor(Kct)was defined,which was important for the establishment of engineering judgment standard of welding imperfection in the laying construction of hydrogen transport pipes.
L245 pipeline steelhydrogen transport pipegirth weldstress concentrationhydrogen embrit-tlement sensitivitycleavage fracture
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