The Effect of Thickness, Welding Metals Sequence and Composition on Residual Stresses in Welding Gas Steel Pipes using LTT filler

Uneven expansion and contraction and the resulting plastic deformation are the main source of residual distortion and stress in welded structures. The distribution of residual stresses in a welded joint depends on factors such as inlet heat, arc welding speed, material properties, preheating, part thickness, groove geometry and welding execution schedule. In this research, a head to head joint is investigated by penetration welding with experimental methods and finite element simulation. Residual stresses are measured by the central hole drilling method and by converting the obtained data into residual stresses, the obtained results are used to verify the developed finite element model. In the finite element model, the non-coupled thermal-mechanical mode is used and the method of birth and death of the elements is used in the simulation of filler materials. In the simulation, the phase transformation process is considered and with the help of LTT filler introduced, the residual stresses in the single-pass welding show a 15% reduction and in the two-pass welding show a 17% reduction in the tensile residual stresses. By examining the effect of the arrangement and composition of the passes and the type of welding fillers, it was found that the combination of LTT electrode with 6010 electrode provides more favorable results for residual stresses. Regarding the effect of thickness change in the cross section of the samples, the output of the results of both numerical analysis software does not show significant changes.