660MW超超临界锅炉末级再热器氧化皮大面积剥落原因分析  

Cause Analysis of Massive Oxidation Scale Exfoliation from Final Reheater in 660 MW Ultra-Supercritical Boiler

作　　者：姚兵印[1] 李志刚[1] 党黎军[1] 张志博[1] 侯召堂[1] 唐丽英[1] 

机构地区：[1]西安热工研究院有限公司,西安市710032

出　　处：《电力建设》2014年第11期132-138,共7页Electric Power Construction

摘　　要：为了掌握某电厂2×660 MW超超临界锅炉在运行1．7～2．0万h后末级再热器多次发生氧化皮大面积剥落、堆积的原因，对该厂2台锅炉的末级过热器、后屏过热器、末级再热器TP347 H管子割管取样分析。割管分析内容包括：化学成分分析、室温拉伸试验、硬度检验、金相检验等。分析结果表明：末级过热器和后屏过热器TP347 H管子内壁存在1层细晶粒区（晶粒度9～10级），而高温再热器则整体均为粗晶区，内壁无细晶粒区。二者晶粒度的区别是导致仅高温再热器发生大面积氧化皮剥落堆积的主要原因。TP347 H钢管晶粒度对其内壁氧化皮长大的速度的影响因素表现为材料晶粒越细小，晶界密度越大，Cr元素通过短路扩散方式的扩散速度越快，越有利于在TP347 H管子内壁形成富Cr的氧化层，其抗蒸汽氧化能力越强。最后，对600℃温度等级的超超临界机组高温受热面的选材提出了建议。To understand the reason of massive oxidation scale exfoliation from the final reheater （RH）tubes of two 660 MW ultra-supercritical （USC）boilers after operating for 1.7 ×10^4 to 20 ×10^4 h,TP347H tubes cut from the final superheater （SH）,3rd SH （rear plate superheater）,and final RH were investigated for chemical compositions analysis, tensile testing at ambient temperature,hardness test,metallographic examination,etc.Microstructure analysis shows that there is a layer of fine grain zone （No.9-10 grade grain size）on the inner surface of the 3rd SH and the TP347H tubes in final SH,but only the coarse grain zone can be seen in final RH.The presence of the coarse grain zone on inside surface of RH tubes causes the massive oxidation scale exfoliation from RH tubes.The grain size of TP347 H tubes has great influence on the forming speed of oxide scale on the inside surface.It is found that fine grain size and high density grain boundaries can increase “short way”Cr element diffusion rates in the TP347 H austenitic steel,thus increasing the resistance to steam oxidation during operating at high temperature.Finally,suggestions on material selections for 600 ℃temperature class USC boiler tubes were presented for consideration.

关 键 词：超超临界机组 末级再热器 氧化皮 晶粒度 抗蒸汽氧化能力 

分 类 号：TM621[电气工程—电力系统及自动化]