Abstract Dissimilar metal welds are commonly used in various types of reactors to connect low alloy steel nozzles and austenitic stainless steel piping systems. To mitigate the degradation of stainless steel pipe welds that are affected by intergranular stress corrosion cracking in BWRs, weld overlays have been implemented to provide the structural reinforcement. They have also been applied to repair dissimilar metal welds at nozzles in BWRs and PWRs. A weld overlay can favorable reverse residual stresses from tensile to compressive around interior of the susceptible materials. The ASME Code Case N-504 series suggest that the evaluation of repaired welds should consider residual stresses that are generated by the weld overlay with other applied loads on the system. This study considers a dissimilar metal weld that joins the low alloy steel nozzle to the stainless steel safe end in a typical PWR, and is to calculate the post-overlay residual stress states using ANSYS finite element analysis software. Based on the stress report and site survey of the hot leg nozzle, models for analyzing residual stresses were developed on various assumptions. Computational results demonstrate that the weld overlay process probably provides compressive distributions of axial and hoop residual stresses at the inside surface of the dissimilar metal weld. The residual stress distributions that are induced by weld overlays of various sizes are compared to determine the effect of weld overlay sizing on the residual stresses in the original weld. The comparison reveals that weld overlay length has a greater effect on residual stresses than weld overlay thickness. As the applied overlay length increases, the compressive residual stresses increase markedly. Each nozzle/safe end design is somewhat unique; using a feasible weld overlay dimension in consideration of technical and economic is necessary. This investigation has provided a reference for optimizing the weld overlay design of dissimilar metal welds in PWRs.

中文翻译：

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堆焊尺寸对压水堆异种金属焊缝残余应力影响的有限元分析

摘要 异种金属焊缝常用于各类反应器中，用于连接低合金钢喷嘴和奥氏体不锈钢管道系统。为了减轻受 BWR 中晶间应力腐蚀裂纹影响的不锈钢管焊缝的退化，已实施堆焊以提供结构加固。它们还被用于修复 BWR 和 PWR 喷嘴处的异种金属焊缝。堆焊可以有利地将敏感材料内部周围的残余应力从拉伸应力逆转为压缩应力。ASME 规范案例 N-504 系列建议对修复焊缝的评估应考虑由堆焊产生的残余应力和系统上的其他应用载荷。本研究考虑了典型压水堆中将低合金钢喷嘴连接到不锈钢安全端的异种金属焊缝，并使用 ANSYS 有限元分析软件计算叠加后的残余应力状态。根据热腿喷嘴的应力报告和现场调查，基于各种假设开发了用于分析残余应力的模型。计算结果表明，堆焊过程可能会在异种金属焊缝的内表面提供轴向和环向残余应力的压缩分布。比较由不同尺寸的堆焊引起的残余应力分布，以确定堆焊尺寸对原始焊缝残余应力的影响。比较表明，与堆焊厚度相比，堆焊长度对残余应力的影响更大。随着覆盖层长度的增加，残余压应力显着增加。每个喷嘴/安全端设计都有些独特；考虑到技术和经济，使用可行的堆焊尺寸是必要的。本研究为优化压水堆异种金属焊缝堆焊设计提供了参考。