Optimizing the Local Strength Mismatch of a Dissimilar Metal Welded Joint in a Nuclear Power Plant

Local strength mismatch is one of the important factors which affects the fracture behavior of a dissimilar metal welded joint (DMWJ). The question to consider is how to improve the fracture resistance of the DMWJ effectively by optimizing the local strength mismatch. In this paper, a DMWJ in a nuclear power plant was selected, the J-resistance (J–R) curve and crack growth path of the DMWJ under different strength mismatches of heat affect zone (HAZ), fusion zone (FZ), and near interface zone (NIZ) were systemically studied. And then, the optimal design of the local strength mismatch was investigated. The results show that decreasing the strength of HAZ and NIZ and increasing the strength of FZ will increase the fracture resistance of a DMWJ. Increasing the strength of FZ increases the J–R curve obviously. When the Ms(HAZ):Ms(FZ):Ms(NIZ) = 1.12:1.4:1.26 and Ms(HAZ):Ms(FZ):Ms(NIZ) = 1:1.4:1, the DMWJs have the highest J–R curves. Considering that the two J–R curves are similar, it is suggested that the fracture resistance of the DMWJ can be improved only by increasing the strength of the FZ.