Residual-stress measurements on multi-pass weldments of stainless-steel piping

This paper presents measurements of the bulk residual stresses in 100-mm (4-in.) and 250-mm (10-in.) diam Schedule 80 piping weldments using strain-relief techniques. Both laboratory-welded specimens and field-welded specimens from reactors in service were studied. Axial bulk residual-stress distributions were obtained at 45-deg intervals around the circumference. At each azimuthal position, the residual stresses were measured at seven axial positions: on the weld center line and 13, 20 and 25 mm to either side of the weld center line, on both the inside and outside surface. The specimens were parted out using a wire-feed electric-discharge machine, and the resulting strain relief was measured with electrical-resistance strain gages (120-deg rosettes). The bulk residual stresses obtained on the inside surface of the 100-mm weldments exhibit an oscillatory distribution with peak values above 275 MPa (40 ksi) and stress gradients normal to the weld on the order of 35 MPa/mm (127 ksi/in.)