Impact of Weld Sequencing and Fabrication on Residual Stress Fields

摘要

Welding is the most commonly used and one of the most important material joining processes widely used in the heavy fabrication industries, particularly in nuclear energy industry. Residual stresses in welded components can reduce the lifetime of nuclear components significantly. Welding residual stresses in nuclear power plants can lead to stress-corrosion cracking concerns; however, the ASME code only accounts for fatigue degradation and not stress corrosion cracking (SCC) in its design criteria although there have been a number of SCC failures and few fatigue failures for primary pressure boundary systems. A number of mitigation strategies have been proposed such as Mechanical Stress Improvement Process (MSIP), Full and Optimized Structural Weld Overlay (FSWOL, OWOL), and Inlay and Onlay cladding. Emc~2 has conducted extensive welding residual stress studies for a series of critical components in the nuclear energy industry. The welds studied here have different groove geometries, different weld and repair sequencing, post-weld heat treatment (PWHT) procedures, among other differences. This paper summarizes these results and further shows how the weld sequencing can impact residual stress fields and could potentially mitigate SCC for future plants. Some general discussion and comments on mitigation of SCC will be included in the paper.