Residual stress measurement in ferritic steel tube welds using X-ray diffraction

Abstract

The X-ray diffraction (XRD) technique has been used to measure the residual stresses before and after post-weld heat treatment in autogenous butt weld joints in 2.25Cr-1 Mo steel tubes. The tubes are used in the steam generator assemblies of fast breeder reactors. Measurement data show that the stress in the weld centre is ~150 MPa maximum. The stress distribution around the weld centre is asymmetrical with larger amounts of compressive stress on the side of the tube sheet block. The stress becomes compressive beyond ~5 mm from the weld centre reaching values of ~200 MPa and more. Post-weld heat treatment (PWHT) at 923 K for 30 min removes most of the residual stresses and PWHT at 988 K for 2.5 h removes all the residual stresses in the weld regions.