350MW亚临界锅炉低温再热器失效分析  

Failure Analysis of 350MW Sub-critical Boiler Low Temperature Reheater

作　　者：张乾乾 张建伟 ZHANG Qianqian;ZHANG Jianwei(China Datang Corporation Science and Technology General Research Institute Co.,Ltd.,Northwest Branch,Shanxi 710021,China)

机构地区：[1]中国大唐集团科学技术研究总院有限公司西北电力试验研究院,陕西西安710021

出　　处：《电焊机》2024年第4期71-76,97,共7页Electric Welding Machine

摘　　要：某电厂350MW亚临界锅炉在进行水压试验时发现低温再热器管与管卡TP310H/T12异种钢焊缝发生了泄漏。通过化学成分分析确认两侧母材化学成分符合标准要求,T12钢侧母材发生2级老化。金相观察发现T12钢侧熔合线存在氧化缺口和孔洞,为焊接接头薄弱区域。异种钢接头化学成分差异导致其抗氧化性降低出现氧化缺口,管卡自身结构为了约束低温再热器管道的移动与膨胀产生的结构应力进一步促进氧化缺口沿管壁扩展;结构性未焊透处熔合线两侧硬度值相差过大促进了裂纹的萌生,扫描电镜分析确认氧化缺口的存在是失效的主要原因。设计时要尽量将异种钢接头用于低应力、低拘束的工况下,及时进行相关检查。During the pressure test of a sub-critical boiler in a power plant,it was found that the weld between the low temperature reheater pipe and the pipe clamp TP310H/T12 dissimilar steel leaked.Based on the analysis of macroscopic morphology,chemical composition,microhardness and microstructure of the failed dissimilar steel pipe samples,it was concluded that the chemical composition of the base metal on both sides meets the requirements,and the base metal on the side of T12 steel undergoes two-level aging.The fused line of T12 steel side is the weak area of welded joints.The chemical composition difference of dissimilar steel joints leads to oxidation resistance.In order to restrain the structural stress of low temperature reheater pipe and further promote the expansion of oxidation notch along the pipe wall.The large difference of hardness values on both sides of fusion line at the incomplete penetration of structure promotes the initiation of cracks.Dissimilar steel joints should be used as far as possible under the working conditions of low stress and low restraint and relevant inspections should be carried out in time.

关 键 词：异种钢焊缝 氧化缺口 失效分析 TP310H T12 

分 类 号：TG441.7[金属学及工艺—焊接]