A methodology of appropriate weld procedures for axial compressive residual stress on inner surface in multi-pass girth welded pipe joint

Weld residual stress and distortion, which often have negative influences on structural performance of welded components, should be controlled appropriately. Especially, weld residual stress in nuclear power plants can be one of the fatal problems as the factor in generation and propagation of stress corrosion cracking (SCC). It has become well known that an axial residual stress on the inner surface of welded pipe joint has a significant influence on SCC. The axial residual stress has been therefore controlled by additional process, such as some kinds of peening or heat treatment. On the other hand, another approaches for the in-process control of the axial residual stress during weld procedure should be also performed if it is technically possible. In this study, a parametric survey on the relationship between welding conditions, including configuration of the pipe joint, and weld residual stress is done by the numerical analysis with the thermal elastic-plastic model. Based on the numerical results, a methodology for controlling the axial residual stress on the inner surface of welded pipe joints is investigated from a viewpoint of the optimization of weld procedure. (author)