通过断口分析、化学成分分析和金相检验等方法对某盘架管路弯管的断裂原因进行了分析。结果表明: 该盘架管路在生产过程中因非正常使用工具校形导致弯管根部存在较大的残余应力；另外,工具校形在弯管表面产生的机械损伤形成了应力集中, 促进了裂纹的萌生；加之弯管焊缝热影响区晶粒粗大降低了该处材料的疲劳强度；上述因素综合作用最终导致弯管在耐久振动试验中于焊接热影响区的机械损伤处发生疲劳断裂。

The fracture reasons for elbow of the shelf line were analyzed by means of fracture analysis, chemical compositions analysis, metallographic examination and other methods. The results show that during production process of the shelf line, in order to correcting the shape of the elbow the un-normal use of the tools caused a big residual stress at the root of the elbow. In addition, stress concentration formed at the mechanical damage marks remained by the non-normal tool straightening, which sped up the crack initiation. At the same time, the coarse grains of the welding heat affected zone of the elbow reduced the fatigue strength of the material. The above factors eventually led to fatigue fracture of the elbow during the durability and vibration test at the mechanical damaged welding heat affected zone of the elbow.