T91+TP347H异种钢焊接接头失效分析

Failure Analysis of T91+TP347H Dissimilar Steel Welded Joints

某电厂超临界锅炉运行中发现高温再热器出口T91/TP347H异种钢焊接接头发生断裂致使锅炉泄漏。对失效焊接接头进行宏观形貌观察、化学成分分析、金相检验、硬度测试等一系列检验,结合该锅炉的运行情况和历史故障情况,综合分析该锅炉异种钢焊接接头的失效原因。结果显示,焊缝成形差、焊接质量不合格是导致出现接头开裂的直接原因;异种钢接头本身化学成分差异大,性能不均匀,在长期的高温和应力作用下发生元素迁移,造成交界面性能下降,这是焊接接头出现开裂的根本原因;机组的深度调峰、频繁启停调峰则进一步加速了裂纹的产生。经过失效原因分析,并借鉴异种钢焊接接头的管理标准及实践经验,建议加强焊接质量控制和优化金属监督策略,提高无损检测的抽样率,并注意控制机组调峰速率。可为同类型电厂异种钢焊接接头管理提供参考。

During the operation of a supercritical boiler in a certain power plant,it was found that the T91/TP347H dissimilar steel welded joint at the outlet of the high-temperature reheater had fractured,causing a boiler leak.A series of tests were conducted on the failed welded joint,including macroscopic morphology observation,chemical composition analysis,metallographic examination,and hardness testing.Combined with the operating conditions and historical fault history of the boiler,a comprehensive analysis was made of the failure causes of the dissimilar steel welded joint.The results showed that poor weld formation and unqualified welding quality were the direct causes of the joint cracking;the large chemical composition difference and uneven performance of the dissimilar steel joint itself,under long-term high temperature and stress,led to element migration,resulting in a decline in interface performance,which is the fundamental reason for the cracking of the welded joint;the deep peak shaving and frequent start-stop peak shaving of the unit further accelerated the generation of cracks.Based on the failure cause analysis,and drawing on the management standards and practical experience of dissimilar steel welded joints,subsequent maintenance inspection and metal supervision strategy optimization suggestions were put forward,which can provide a reference for the management of dissimilar steel welded joints in similar power plants.