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某蒸汽换热器环管接头正常工作9-13个月后即在集管与盘管焊缝处出现开裂,通过光学显微镜、洛氏硬度计和万能试验机对环管接头进行分析,环管接头分为盘管区、集管区、焊缝区及热影响区。结果表明:在焊缝区形成的细晶铁素体使得组织细化,导致焊缝区硬度增强;热影响区的晶粒粗大,硬度最低,与相邻的焊缝区产生强度差,使应力集中在热影响区,并且热影响区有较多的非金属夹杂物,从而导致在热影响区产生裂纹源使得环管接头断裂失效。
A steam heat exchanger ring joints work normally after 9-13 months in the header and coil weld cracks appear, through the optical microscope, Rockwell hardness tester and universal testing machine ring connector analysis, loop Joints are divided into coil area, header area, weld zone and heat affected zone. The results show that fine-grained ferrite formed in the weld zone leads to the refinement of the microstructure, which leads to the increase of the hardness of the weld zone. The heat-affected zone has coarse grains with the lowest hardness and poor strength with the adjacent weld zone, Concentrated in the heat affected zone, and the heat affected zone has more non-metallic inclusions, resulting in cracks in the heat-affected zone causes cracks in the ring joint failure.