Measured and predicted residual stresses in thick section electron beam welded steels

Four steel thick-section components, created by electron beam (EB) welding, were measured to obtain their residual stress distributions. Two components were made from ferritic steel and two components manufactured from stainless steel. All four components were measured in the as-welded state, with one ferritic steel component then subjected to post-weld heat treatment (PWHT) and measured. Distributions of the principal residual stresses were measured, across the EB welds and through the weld centrelines. Finite element models simulated the welding processes and the predicted residual stresses were compared to the measurements. In the ferritic steel components it was found that the peak residual stresses occur either side of the weld outside of the heat affected zone, with magnitudes corresponding to parent material yield strengths. After PWHT the measured peak stresses reduced from about 600 MPa to 90 MPa. Compressive residual stresses were found at the EB weld entrance and exit positions of the ferritic steel. This was not observed in the stainless steel EB welds, where tensile stresses were measured in the as-welded state. Overall the profiles of the residual stresses predicted by FE analyses replicated the measurements, but the FE analyses always predicted higher peak values. It was found that the measured distribution of residual stresses across the ferritic steel components are very similar irrespective of component thickness and weld speed, with the tensile stresses confined to distances of about 40% of the component thickness. In contrast in a stainless steel component the tensile stresses are much more broadly distributed about the weld centreline.