X-ray Investigation of the Effect of Machining Condition on Residual Stress Distribution due to Welding after Surface Machining

抄録

In nuclear power plants, the high tensile residual stress introduced by welding after surface machining may be an important factor in the occurrence of stress corrosion cracking in welds of low-carbon austenitic stainless steel type SUS316L. This study investigated the effect of machining conditions on variations in the distributions of residual stress introduced through surface machining and sequential welding. First, in experiments, test specimens were prepared by surface machining under different machining conditions. Then, bead-on-plate welding under the same welding conditions was conducted on the test specimens with different surface machined layers. The residual stress variations were evaluated by X-ray diffraction method. As a result, the residual stress introduced by surface machining showed nearly uniform distributions and varied drastically depending on the machining conditions. After welding, the welding longitudinal residual stress had a maximum tensile stress in the heat affected zone and the values of residual stress were independent of the residual stress due to surface machining. Based on the Vickers hardness testing results, we concluded that the magnitude of the maximum residual stress introduced by welding after surface machining is strongly dependent on the degree of work hardening due to surface machining.