Prediction of welding residual stress in multi-pass butt-welded modified 9Cr–1Mo steel pipe considering phase transformation effects

The objective of this paper is to investigate the influence of solid-state phase transformation on the evolution of residual stress distributions in butt-welded modified 9Cr–1Mo steel pipes. A thermal elastic plastic finite element model taking into account the metallurgical phase transformation was developed. Effects on welding residual stress of the volumetric change and the yield strength change due to austenite–martensite transformation were investigated by means of numerical analysis. The simulated results show that the volumetric change and the yield strength change due to martensite transformation have influences on the welding residual stress. The former not only changes the magnitude of residual stress, but also alters the sign of residual stress in the weld zone; and the later only changes the magnitude of residual stress. In the cases in which the volumetric change due to phase transformation is considered, the simulated results are generally in good agreement with the experimental measurements.