Influence of welding material strength on strain capacity of girth welds in high-grade steel pipelines

In order to evaluate the influence of the strength of base material, root welding material and filler material on the strain capacity of girth welds in X80 pipeline, the passivation behavior of crack tips during cracking was accurately simulated with the Key Hole model by the nonlinear finite element method based on the China–Russia Eastern Gas Pipeline with a diameter of 1 422 mm and a wall thickness of 21.4 mm. Here, consideration was given to the complete geometrical morphology of welded joints and the partition of four materials with different properties. In addition, the crack initiation behavior of circumferential cracks in the root inner surface under the action of tensile load was researched. According to the results, the strength of root welding material has little impact on the overall strain capacity of double V-groove welded joint, which can be ignored. The overmatching of filler material with the base material is the most important to guarantee the strain capacity in the weld zone. Moreover, in the case that it is difficult to enhance the strength of filler material, limiting the strength indicator of base material is an effective way to improve the strain capacity of welded joints in high-grade steel pipelines.