核电接管安全端308L/309L异种金属焊接接头拉伸断裂行为

Tensile fracture behavior of nuclear safe-end 308L/309L dissimilar metal welded joints

对核电接管安全端异种金属焊接接头（SA508-3-308L/309L-316L）进行拉伸、硬度试验及显微组织观察,确定接头拉伸断裂位置并研究断裂位置产生原因。结果表明：焊缝在接头具有最低强度及塑性,断裂位置为焊缝隔离层;隔离层中铁素体大部分呈板条状,因此隔离层裂纹扩展穿透两相界面相对较少,裂纹扩展阻力更小;隔离层相对于对接焊缝硬度更高,隔离层具有高的位错密度,因此残余应力大,导致硬度升高,降低隔离层临界塑性变形能力;焊缝与SA508-3钢为低强度匹配,高的三轴应力及塑性应变主要分布在隔离层内,裂纹更易萌生。

The tensile,hardness test and microstructure observation of SA508-309 L/308 L-316 L dissimilar metal welded safe-end joints（DMWJs） were carried out,and the tensile fracture position of the joints was determined and the cause of fracture position was studied.The results show that the weld seam has the lowest strength and ductility in the joints,and the fracture position is the buttering layer of the weld seam.The ferrite in the buttering layer is lath-shaped;so the crack propagation in the buttering layer penetrates the two-phase interface relatively less,and the resistance of crack propagation is even smaller.The buttering layer has higher hardness compared with the butt weld seam,and the buttering layer has high dislocation density.Therefore,the residual stress is large,resulting in the increase of hardness and the critical plastic deformation ability of the buttering layer.The weld seam and SA508-3 base metal have low strength matching,and the high triaxial stress and plastic strain are mainly distributed in the buttering layer,and the crack is more prone to initiation.