Effect of Welding Conditions on Residual Stress and Stress Corrosion Cracking Behavior at Butt-Welding Joints of Stainless Steel Pipes

Abstract

Stress corrosion cracking (SCC) in Type 316 L low-carbon austenitic stainless steel recirculation pipes have been observed near butt-welding joints. These SCC in Type 316 L stainless steel grow near the welding zone mainly because of the high tensile residual stress caused by welding. Therefore, for SCC growth analysis, it is important to assess the residual stress caused by welding of stainless steel piping. In the present study, which is focused on the scatters of welding parameters such as heat input and welding speed, these values were measured experimentally by fabricating a series of butt-welded specimens of Type 316 pipes. The distribution and scatter of residual stress were also measured by stress relief and X-ray diffraction methods. The effects of welding parameters on residual stress distribution have been evaluated through welding simulations based on finite-element analysis using three-dimensional and axisymmetric models. Parametric analyses were also performed, while taking into account the variation of some welding parameters based on the experiments. SCC growth behavior was calculated using simulated residual stress distributions and applying a procedure in the fitness-for-service code. It was clearly shown that the uncertainties on welding heat input and speed have strong influences on SCC growth behavior because residual stress is also affected by the scatter of these welding parameters.