The Variability in Weld Residual Stress

Abstract

Residual stresses resulting from welds are a key consideration in the design and assessment of piping and pressure vessels. As welding is a variable process, the resulting variability in weld residual stress should be accounted for in design and assessment. This paper investigates the variability in residual stress resulting from flux cored arc welds by performing residual stress measurements on a set of nominally identical welds between 25mm plates of grade DH36 steel. The welds were produced in two environments to assess the impact on residual stress variability: a well-controlled laboratory environment and a less controlled factory environment. The results showed significant variability in the residual stresses between the welds, with standard deviations up to 25% of the peak value in some locations near the weld center. The welds were two sided and higher variability was measured in the side performed second, with the variability in heat applied appearing to be a key driver of the residual stress variability. A difference was observed between the standard deviations of residual stress in the factory and laboratory samples, with the laboratory samples showing less residual stress variability. Whilst the small number of samples measured prevents firm quantitative conclusions being drawn about the potential differences in residual stress variability between production environments the results do suggest that there is value in further study.