600MW超临界机组屏式过热器管爆管分析
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摘要
通过对爆管样品的宏观形貌分析、化学成分分析、硬度检验、金相组织检验和扫描电镜分析,对某超临界机组T91材质的屏式过热器爆管原因进行分析。结果表明,爆管试样硬度偏低,这与显微组织的变化相关。T91钢的正常供货组织应为回火马氏体,而爆管样品爆口处的金相组织显示马氏体板条位向消失,演变为铁素体和于晶界处析出的颗粒较大的碳化物。屏式过热器管超温服役,导致材料组织老化,综合力学性能下降,在高温高压蒸汽作用下发生失效,造成泄漏。
The burst cause of a platen superheater tube of T91 steel in certain supercritical units was analyzed by macroscopical morphology,chemical composition,hardness test,OM and SEM observation using the specimens exploded platen superheater tube.Results show a low hardness of the failed tube which is related to the microstructure transformation.The metallographic structure of T91 steel is tempered martensite,while the metallographic structure of the exploded tube doesn't show any martensite at all.The martensite lath is evolved into ferrite and coarsen carbides precipitated at grain boundry.The overheat operation of superheater tube causes the microstructure degradation and the decrease of mechanical properties,and finally causes the leakage of platen superheater tube under the condition of high temperature and pressure steam.
The burst cause of a platen superheater tube of T91 steel in certain supercritical units was analyzed by macroscopical morphology,chemical composition,hardness test,OM and SEM observation using the specimens exploded platen superheater tube.Results show a low hardness of the failed tube which is related to the microstructure transformation.The metallographic structure of T91 steel is tempered martensite,while the metallographic structure of the exploded tube doesn't show any martensite at all.The martensite lath is evolved into ferrite and coarsen carbides precipitated at grain boundry.The overheat operation of superheater tube causes the microstructure degradation and the decrease of mechanical properties,and finally causes the leakage of platen superheater tube under the condition of high temperature and pressure steam.
引文
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[2]钟万里,赵君,王伟,等.T91钢的回火工艺分析及其组织评定[J].金属热处理,2012,37(03):94-98.Zhong Wanli,Zhao Jun,Wang Wei,et al.Tempering process analysis and microstructure assessment of T91steel[J].Heat Treatment of Metals,2012,37(03):94-98(in Chinese).
[3]赵彦芬,张路,赵林凤,等.国产T91钢在高温受热面中的应用评价[J].中国电力,2009,42(10):5-11.Zhao Yanfen,Zhang Lu,Zhao Linfeng,et al.Assessment of domestic T91 steel applied on high-temperature surface[J].Electric Power,2009,42(10):5-11(in Chinese).
[4]王学,张珣,占良飞,等.T91钢组织退化行为及对高温持久强度的影响[J].中国电机工程学报,2012,32(29):137-142.Wang Xue,Zhang Xun,Zhan Liangfei,et al.Micresructure degradation behavior and its influence on high temperature stress rupture limit of T91 steel[J].Proceedings of the CSEE,2012,32(29):137-142(in Chinese).