电站锅炉过热器管焊缝开裂失效分析  

Failure analysis of welding seam cracking of superheater tube of power station boiler

作　　者：刘天佐 刘献良 赖云亭[2] 马芹征 LIU Tianzuo;LIU Xianliang;LAI Yunting;MA Qinzheng(Technical Service Branch of Huadian Power International Co.,Ltd.,Jinan 250014,China;Suzhou Nuclear Power Research Institute Co.,Ltd.,Suzhou 215004,China)

机构地区：[1]华电国际电力股份有限公司技术服务分公司,山东济南250014 [2]苏州热工研究院有限公司,江苏苏州215004

出　　处：《电力科技与环保》2022年第4期294-299,共6页Electric Power Technology and Environmental Protection

基　　金：广东省基础与应用基础研究重大项目(2019B030302011);国家自然科学基金(U1867215)。

摘　　要：为了探究某火电厂335MW亚临界锅炉分隔屏过热器管与托块焊接焊缝开裂的原因,采用宏观检查、化学成分分析、力学性能测试、金相检验、能谱分析等方法和试验进行了分析。结果表明:(1)管子化学成分中C、Si、Mn、P、S、Cr、Mo、V元素含量均满足GB/T5310-2017要求;管子室温平均抗拉强度524MPa、屈服强度340MPa,断后伸长率31.0%,力学性能符合标准要求;(2)金相组织2级轻度老化,可排除长时过热或短时过热导致管子开裂情况;(3)熔合区偏析带能谱分析及元素线扫描结果显示偏析带出现了C元素含量显著升高的趋势。结合开裂部件在锅炉中的位置布置及受力情况,综合分析后得出了焊缝开裂的原因:开裂焊缝所在管排频繁晃动,在管子与托块的角焊缝部位产生了较高的应力集中;管子和奥氏体焊缝的熔合区发生了碳元素的迁移,引起熔合区性能劣化,导致在熔合区产生蠕变裂纹。根据分析结论,提出了采用镍基合金焊材、增加托块数量来分散受力、优化管子与托块的焊接结构等措施,以减小焊趾应力集中,减缓裂纹形成的相应建议。In order to find the cause of the cracking problem of the welding seam between the superheater tube and the support block of the partition row of a thermal power boiler,macro inspection,chemical composition analysis,mechanical properties test,metallographic inspection,energy spectrum analysis and other tests were carried out on the samples of the cracked parts.The results show that(1)the contents of C,Si,Mn,P,S,Cr,Mo,and V elements in the chemical composition of the tube all meet the requirements of the standard GB/T 5310-2017.The average tensile strength of the tube at room temperature is 524Mpa the yield strength is 340Mpa and the elongation after fracture is 31.0%,which meets the requirements of the standard GB/T5310-2017.(2)Metallographic structure aging level 2,which indicates that there is no problem of long-term overheating or short-term overheating.(3)The results of the fusion zone segregation band energy spectroscopy and the line scan results of Fe,Cr and C showed that the C element content in the segregation zone had a significant increase in the C element content.Combined with the position arrangement and force of the cracked parts in the boiler,the cause of weld cracking is derived after comprehensive analysis.The tube row where the cracked weld is located frequently shakes,resulting in high stress concentration at the fillet weld between the tube and the support block.Carbon migration occurs in the fusion zone of the tube and austenitic weld,which causes the deterioration of the performance of the fusion zone and creep cracks.According to the analysis conclusion,some suggestions are put forward,such as adopting nickel-based alloy welding materials,increasing the number of support blocks to disperse the stress,and optimizing the welding structure of the tube and the support blocks,etc.,to reduce the stress concentration of the weld toe and slow down the formation of cracks.

关 键 词：12CR1MOVG 异种钢焊接 碳迁移 疲劳开裂 蠕变裂纹 

分 类 号：TK229[动力工程及工程热物理—动力机械及工程] TB31[一般工业技术—材料科学与工程]