• CSCD核心库收录期刊
  • 中文核心期刊
  • 中国科技核心期刊

电力建设 ›› 2014, Vol. 35 ›› Issue (11): 132-138.doi: 10.3969/j.issn.1000-7229.2014.11.023

• 发电技术 • 上一篇    

660 MW超超临界锅炉末级再热器氧化皮大面积剥落原因分析

姚兵印,李志刚,党黎军,张志博,侯召堂,唐丽英   

  1. 西安热工研究院有限公司,西安市 710032
  • 出版日期:2014-11-01
  • 作者简介:姚兵印(1971),男,硕士,高级工程师,主要从事火电厂、水电厂、风电场金属材料焊接修复及新材料性能研究、金属监督管理与失效分析; 李志刚(1952),男,研究员,主要研究方向为电厂化学与水处理、材料腐蚀与防护技术; 党黎军(1963),男,研究员,现任西安热工研究院有限公司电站技术监督部副总工程师,长期从事锅炉燃烧与运行优化、故障诊断、锅炉及节能技术监督研究; 张志博(1982),男,硕士,高级工程师,主要从事火电厂、水电厂、风电场金属监督管理与失效分析工作; 侯召堂(1980),男,本科,高级工程师,从事火力发电厂重要部件的无损检测与寿命评估工作; 唐丽英(1978),女,硕士,高级工程师,主要从事火电厂新新材料性能研究与失效分析。

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

 

YAO Bingyin, LI Zhigang, DANG Lijun, ZHANG Zhibo, HOU Zhaotang, TANG Liying
  

  1. Xi’an Thermal Power Research Institute Co., Ltd., Xi’an 710032, China
  • Online:2014-11-01

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TP347H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TP347H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。TP347H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TP347H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。

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

Abstract:

 

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 1.7×104 to 20×104 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 TP347H 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 TP347H 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.

Key words: ultra-supercritical unit, final reheater, oxide scale, grain size, resistance to steam oxidation