An Efficient Method for Estimation of Reduction of Welding Residual Stresses from Stress-Relief Annealing (Report Ⅳ) - Applicability of the Method for Stress-Relief Annealing of Thick Welded Joints

摘要

Stress-relief annealing (SR treatment) is included in the fabrication process of welded structures such as pressure vessels. This study aims to develop a simple analytical method to facilitate the calculation of transient and residual stresses during SR treatment, in order to easily determine the reasonable conditions for SR treatment of recent large-size structures of high-quality thick plates. In the first report, estimation equations for uni-axial stress state were formulated for relaxation tests at changing and constant temperatures. In the second report, the stresses relaxed by SR treatments in thick welded joints were analyzed accurately by the finite element method based on thermal elastic-plastic creep theory. The characteristics of the changes in the welding residual stresses in multi-axial stress states were studied in detail. In the third report, estimation equations for multi-axial stress state were developed for thick welded joints, based on the above characteristics. In this report, the stress relaxation phenomena of thick welded joints during SR treatment are analyzed by applying the estimation equations. The accuracy of the method is investigated, comparing the results with ones by FEM.