超超临界锅炉过热器连通管焊接接头开裂原因分析与处理

Analysis and treatment of welding joint cracking of ultra supercritical boiler superheater pipe

从焊接工艺、接头使用工况、裂纹形貌、设备结构等方面分析某在役发电厂低温过热器至分隔屏过热器连通管焊接接头开裂的原因。结果表明,焊接接头HAZ晶粒粗大,伴有应力集中,存在多种应力叠加形成的峰值应力,同时又处于再热裂纹敏感温度范围内,在峰值应力的作用下发生应力松驰而开裂。提出了有效的修复工艺及防治措施,为企业防治类似问题提供参考依据。

In view of welding process,joint condition,crack shape,and facility structure,analyzes the causes for cracking of weld joints of connecting pipes from low-temperature superheater to pendant superheater at a power plant in operation. The results show that weld joints are exposed to stress concentration with coarse HAZ grains while various stresses overlap to create peak stress within the sensitive temperature of reheat cracking. Thus,the peak stress leads to loosening stress and results in cracking. To avoid such problems,a few effective repair procedures and preventive countermeasures are proposed,providing reference for enterprises to prevent and control similar problems.