某锅炉12Cr1MoVG钢过热器管开裂失效的原因  

Failure Causes of Cracking of 12Cr1MoVG Steel Superheater Tube in a Boiler

作　　者：吴婷 湛立宁 卢俊文 陈敏 周璐璐 WU Ting;ZHAN Lining;LU Junwen;CHEN Min;ZHOU Lulu(Hebei Province Specialized Equipment Supervision and Inspection Research Institute Tangshan Branch,Tangshan 063000,China)

机构地区：[1]河北省特种设备监督检验研究院唐山分院,唐山063000

出　　处：《腐蚀与防护》2024年第5期99-104,共6页Corrosion & Protection

基　　金：河北省市场监督管理局科技计划项目(2023ZD13)。

摘　　要：某电站锅炉12Cr1MoVG钢过热器管运行半年即发生爆管开裂。为查明其开裂原因,采用形貌观察、化学成分检测、力学性能试验、硬度测试、非金属夹杂物分析、显微组织分析等方法,对过热器管进行了失效分析。结果表明:过热器管冷弯成型后未进行热处理以消除应力,且弯管内壁有微裂纹等加工缺陷;在服役过程中管子内壁氧化层大幅降低了传热效率,导致过热器管超温运行,从而使金属发生脱碳,降低了金属的耐腐蚀性能;炉水中Na_(3)PO_(4)含量和碱度超标,弯管内壁氧化层中游离态碱离子沉积并浓缩形成碱液,使过热器管在加工缺陷处产生碱应力腐蚀,在弯曲应力作用下过热器管发生沿晶界开裂。A 12Cr1MoVG steel superheater tube of a power plant boiler burst and cracked after half a year of operation.In order to identify the cause of the cracking,the failure analysis of superheater tube was carried out by means of morphology observation,chemical composition detection,mechanical property test,hardness test,nonmetallic inclusion analysis and microstructure analysis.The results show that the superheater tube did not undergo heat-treatment for stress relief after cold bending,and there were machining defects such as micro-cracks on the inner wall of the bent tube.During service,the oxidation layer on the inner wall of the tube greatly reduced the heat transfer efficiency,resulting in overheating operation of the superheater tube,thus decarbonizing the metal and reducing the corrosion resistance of the metal.The Na_(3)PO_(4)content and alkalinity in the furnace water had exceeded the standard.The alkali solution formed by the deposition and concentration of free alkali ions in the oxide layer of the inner wall of the bending tube,which caused alkali stress corrosion to the superheater tube at the processing defect.And the superheater tube cracked along the grain boundary under the action of bending stress.

关 键 词：12Cr1MoVG钢 过热器管 脆性断裂 碱应力腐蚀 脱碳层 

分 类 号：TG111.91[金属学及工艺—物理冶金]