| In this paper, the intergranular corrosion performance of the stainless steel (E308L) welding materials for domestic nuclear power was evaluated using the E method in the GB/T4334-2008《Metal and Alloy-Intergranular corrosion test method for stainless steel》 namely sulfuric acid-copper sulfate boiling solution soak method, the results were analyzed through microscopic observation and energy spectrum analysis. The finite element method (FEM) based on GTN damage model was used to simulate the bending process of corrosion specimen, for the purpose of investigating the influencing factors of bending assessment method for intergranular corrosion. The finite element method (FEM) based on GTN damage model was also used to investigate the effects of initial dual-cracks location on the fracture behavior of dual-cracks in the dissimilar metal welded joints (DMWJ) plate. The coalescence condition of dual-cracks and the effects of material strength mismatch and weld width on it were analyzed. The main conclutions are as following:(1) According to the E method in the GB/T4334-2008, intergranular corrosion tests were conducted for three kinds of domestic stainless steel welding materials (welding electrods E308L-16, welding wire ER308L and welding strip EQ308L) for nuclear power with sensibilisation treatment or not. The result of the bending method are consistent with that of optical observation method, and both methods did not display any intergranular corrosion crack. The energy spectrum analysis shows that no Cr lack zone exists in grain boundaries, and this is the reason of no intergranular corrosion crack. It indicates that the intergranular corrosion resistance and bending toughness of the three welding materials is good, and the GB/T4334-2008is applicable to the intergranular corrosion evaluation of the welding materials.(2) In the bending tests, the tensile plastic strain in the specimens increases with increasing the bending angle and decreasing the pressure head diameter, and the specimens become to be easier to crack. Cracks may initiate during bending process for some stainless steels with lower plasticity, toughness and fracture resistance. So the effects of bending angle, pressure head diameter, and mechanical properties of materials on the bending assessment results for intergranular corrosion should be considered(3) The interaction between dual-cracks in nuclear power DMWJ affects the distribution of stress and strain along the crack tips and the coalescence behavior of dual-cracks. The relative position between the dual-cracks influence the extent of interaction, and then affect the difficulty of coalescence. The coalescence condition of dual-cracks is related to S (the distance of crack tips in the direction along the crack surface), h (the distance of crack surfaces), c (the crack length) and the crack location.When h<2.44c+0.62S, dual-cracks in Alloy52Mw zone will coalesce during the crack propagation; and when h<2.4c+0.514S, dual-cracks in the interface zone between Alloy52Mw and316L will coalesce during the crack propagation.(4) The fracture behavior of dual-cracks is related to the strength mismatch factor M (ratio of the strength of weld metal to base metal). With increasing the M, the maximum load that DMWJ can bear increases, the energy absorbed during fracture increases firstly, and then decreases, finally increases.The lowest energy occurred at M=1.3, and the dual-cracks are most easy to coalesce. The impact of weld width on the fracture behavior of DMWJ is small under high mismatch condition. But under low mismatch condition, the plastic strain and stress triaxiality in weld zone become higher, and with increasing weld width the weld zone becomes easier to fracture and the dual-cracks become harder to coalesce. |
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