Dissimilar metal welds (DMW) are used to connect the low-alloy steel (LAS) pressure vessel and austenitic stainless steel (ASS) piping in nuclear power reactors. DMWs inherently have high gradient of carbon content across fusion boundary (LAS-ASS), leading to carbon migration from LAS to ASS. Nickel-based alloy is the preferred buttering and welding consumable to minimize carbon migration. Stress-relieving treatment after buttering of LAS also enhances the carbon migration, which may lead to a reduction in local fracture toughness in heat affected zone (HAZ) of LAS. Therefore, this paper aims to study the effect of stress-relieving treatment on the fracture toughness behavior of DMW. Fracture toughnesses of different zones of DMWs have been quantified in as-welded and stress-relieved conditions. It has been shown that stress-relieving leads to lowering of fracture toughness with respect to as welded condition. This is attributed to increase in the microstructural heterogeneity in HAZ (LAS) and near fusion boundary of the DMW.

中文翻译：

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异种金属（SA508 Gr.3 Class 1 和 SA312 Type 304LN）焊接接头的断裂韧性行为：有无应力消除处理

异种金属焊缝 (DMW) 用于连接核动力反应堆中的低合金钢 (LAS) 压力容器和奥氏体不锈钢 (ASS) 管道。DMW 本质上具有跨融合边界 (LAS-ASS) 的高碳含量梯度，导致碳从 LAS 迁移到 ASS。镍基合金是首选的黄油和焊接耗材，可最大程度地减少碳迁移。LAS 脱脂后的应力消除处理也增强了碳迁移，这可能导致 LAS 热影响区 (HAZ) 局部断裂韧性的降低。因此，本文旨在研究去应力处理对DMW断裂韧性行为的影响。DMWs 不同区域的断裂韧性已在焊态和应力消除条件下进行量化。已经表明，相对于焊接条件，应力消除导致断裂韧性降低。这归因于 HAZ (LAS) 和近 DMW 融合边界的微观结构异质性增加。