Residual Stress Measurements in Large Scale Component Sections

Neutron diffractometer Engin-X at ISIS was used use in this study to investigate the residual stresses in a section of a multi-pass girth welded thick pipe, of nominal thickness 62 mm, which was made of a ferritic-martensitic steel denoted type P92. Measurements in such large component sections are rare, and have driven the neutron diffraction method to the edge of its capabilities. Significant stresses of over 150 MPa have been found in this pipe section, though post weld heat treatment has been performed. The influences of these welding residual stresses in components at operating temperatures are discussed in terms of their relaxation and high temperature fracture behaviour.