Residual Stress Assessment in Spiral Steel Pipe with the Grade of API-X65 after Submerged Arc-welding

In this study, residual stresses in a finite sample separated from the seamweld of an API pipe with a large diameter were studied for the first time. A finite element simulation of the welding process was conducted to achieve a safe dimension for this sample. After validation of the results, residual stresses were obtained in different directions in this way. Residual stress distribution in the thickness direction represented for the first time is important; firstly, based on standards the accuracy of centralholedrilling results depends on it. Secondly, this distribution sheds light on the 3D equilibrium of residual stresses. The results show that a finite sample with the size of 320×440 mm separated from the main pipe is appropriate for doing the centralholedrilling test which is a significant achievement. It is also proved that the maximum value of residual stresses takes place on surfaces of the sample, while the minimum of this figure was reported in the middle of the thickness. This achievement ensures that the maximum and critical values of residual stresses are obtained by the CHD technique.