304不锈钢管管套装搭接焊接结构失效分析

Failure Analysis of 304 Stainless Steel Pipe to Pipe Lap Welded Structure

为了探寻304不锈钢管管套装搭接焊接结构失效的内在原因及机理,对失效件进行了化学成分检测、金相组织和断口形貌观察,并结合焊件自身的结构特点进行了综合分析。分析认为,该结构焊件在通液薄壁管外径与厚壁管内径及两者连接焊缝背面根部的位置易产生应力集中,加之该处是熔合线位置,组织均匀性较差,更易导致结构件开裂,一旦起裂,在集中应力的作用下裂纹会快速扩展,其断裂失效模式是疲劳脆性断裂。

In order to explore the internal cause and mechanism of the failure of the 304 stainless steel pipe to pipe lap welded structure,the chemical composition,microstructure and fracture morphology of the failure parts were detected,and the structural characteristics of the welding parts were analyzed.The analysis shows that it is easy to produce stress concentration in the position of outer diameter of liquid thin wall pipe,inner diameter of thick wall pipe and the root of the back of the weld connecting them.In addition,it is the location of the fusion line where the microstructure uniformity is poor,which is more likely to lead to the crack of the structural part.Once the crack starts,the crack will expand rapidly under the action of concentrated stress.The failure mode is fatigue brittle fracture.