百万千瓦核电机组高压缸主蒸汽进汽管线焊接接头断裂原因分析  

Analysis of the cause of fracture of the welded joint of the main steam inlet pipeline of the high-pressure cylinder of a million-kilowatt nuclear power unit

作　　者：汤恒 邓江勇 曾勇 李尚昱 银帮耀 Tang Heng;Deng Jiangyong;Zeng yong;Li Shangyu;Yin Bangyao(Guangxi Fangchenggang Nuclear Power Co.,Ltd.,Fangchenggang 538001,Guangxi,China;Suzhou Nuclear Power Research Institute Co.,Ltd.,Suzhou 215004,Jiangsu,China)

机构地区：[1]广西防城港核电有限公司,广西防城港538001 [2]苏州热工研究院有限公司,江苏苏州215004

出　　处：《焊接》2024年第10期74-80,共7页Welding & Joining

摘　　要：【目的】某核电机组满功率运行期间,高压缸主蒸汽进汽管线VVP4001MP焊接接头断裂泄漏,对其焊接接头断裂原因进行研究分析。【方法】通过宏观形貌检查、化学成分分析、金相检验、力学性能测试、扫描电镜断口分析、安装焊接文件复核、振动测试、疲劳寿命计算、装配应力分析和管道结构静强度计算等方法,对断裂焊接接头进行综合分析。【结果】结果表明,失效焊接接头化学成分满足GB/T 14976要求;母材硬度均值为172 HV10;焊缝断裂区域金相组织正常,未见裂纹、未熔合等焊接缺陷;焊接接头几何尺寸与工艺及标准要求存在一定偏差,轴向焊脚尺寸小于工艺卡要求最小值,支管插入深度小于ASME标准;断口分析表明,焊接接头裂纹由焊趾处启裂,以疲劳方式扩展;计算VVP4001MP管座插套焊的疲劳寿命为3658 d,不满足设计安全运行40 a的要求;根部焊缝结构应力不存在超标的情况;射线探伤检验(Radiographic testing,RT)底片显示VVP4001MP母管支管座与插管轴线存在明显夹角,结合现场施工逻辑推断出焊接接头装配时存在强力组对问题。【结论】VVP4001MP管线的断裂性质为高周疲劳断裂,裂纹在焊趾应力集中处萌生,焊接接头断裂的根本原因除与管线固有振动相关外,还与新增焊接强力组对应力相关,二者共同作用促进了裂纹的快速萌生和扩展,而焊脚尺寸不足是造成断裂的促成因素。[Objective]During the full power operation of a certain nuclear power unit,the welded joint of the VVP4001MP main steam inlet pipeline of the high-pressure cylinder broke and leaked,and the reasons for the welded joint fracture were studied and analyzed.[Method]The comprehensive analysis of fractured welded joints was conducted by macroscopical appearance inspection,chemical composition analysis,metallographic examination,mechanical property testing,scanning electron microscopy fracture analysis,installation welding document review,vibration testing,fatigue life calculation,assembly stress analysis,and pipeline structure static strength calculation.[Result]The results indicated that the chemical composition of the failed welded joint meeted the requirements of GB/T 14976.The average hardness of the base material was 172 HV10.The metallographic structure of the fracture area of the weld was normal,and no welding defects such as cracks or lack of fusion were found.However,there was a certain deviation between the geometric dimensions of the welded joint and the requirements of the process and standards,axial weld foot size was smaller than the minimum required by the process card,and the insertion depth of the branch pipe was smaller than the ASME standard.Fracture analysis showed that the cracks in the welded joint originated from the weld toe and propagate in a fatigue manner.The fatigue life of VVP4001MP socket welding was calculated to be 3658 d,which did not meet the requirement of 40 a of safe operation in the design.There was no excessive stress in the root weld structure.The RT film showed that there was a significant angle between the VVP4001MP main pipe branch socket and the insertion pipe axis,and based on the on-site construction logic,it was inferred that there was a strong pairing problem during the welding joint assembly.[Conclusion]The fracture property of VVP4001MP pipeline was high cycle fatigue fracture,with cracks initiating at the stress concentration point at the weld toe.The root cause of wel

关 键 词：主蒸汽管线 焊接接头 振动 疲劳断裂 强力组对 

分 类 号：TG405[金属学及工艺—焊接]