Numerical Evaluation of Weld Pool Size, Distortion and Residual Stresses in Electron Beam Weld Joint of Thick SA312 Type 304 L Pipe and its Validation

Now-a-days, electron beam welding is extensively used in piping and pressure vessel of nuclear industry because of its advantages with respect to no use of filler material, lower distortion and residual stresses. Therefore, the paper aims to evaluate weld pool size, deformation and residual stresses in 13.5 mm thick pipe weld of outer diameter 170mm made of austenitic stainless steel (SA312 Type 304L) in a butt joint configuration prepared by Electron Beam Welding (EBW). Pipe weld with back plate has been prepared by EBW with heat input 825 and 700 J/mm and qualified as per requirements of ASME Sections III. Post-welding, axial distortion, depth of penetration, weld width, and weld area have been measured. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis of pipe weld joint has been performed to predict the weld pool size (weld depth penetration and weld width) and axial distortions. Experimental and predicted results with respect to weld pool size and distortions compares well which confirms the validity of the numerical analysis procedure. After validating the numerical analysis procedure, effect of beam power (heat inputs) on weld residual stresses on pipe weld joint have been evaluated by carrying out numerical analyses. The results showed that lower beam power input resulted in reduced weld pool size, residual stresses and HAZ. The residual stresses in pipe weld joint have been compared with available studies in literature for different welding processes such as multi-pass arc welding, gas tungsten arc welding (GTAW) for approximately same pipe diameter to thickness ratio. It has been found that the residual stresses, distortion, weld pool size and HAZ in the pipe weld joint of EBW are lower compared to other welding processes. It has also been brought out that beam input power of 600J/mm is sufficient for manufacturing pipe weld joint of thickness 13.5 mm. Details of the studies are elaborated in this paper.