长时高温时效对T23水冷壁焊接接头CGHAZ微观组织的影响
Effect of long term high temperature aging on CGHAZ mi-crostructure of T23 water wall welded joint
尹少华 1王煜伟 2孙志强 3张振华4
作者信息
- 1. 苏州热工研究院有限公司,苏州, 215004;天津大学,天津, 300350
- 2. 国家能源集团江苏电力有限公司,南京, 210036
- 3. 苏州热工研究院有限公司,苏州, 215004
- 4. 国能徐州发电有限公司,徐州, 221166
- 折叠
摘要
通过高温时效方法分析了焊后未热处理T23水冷壁管焊接接头粗晶热影响区(coarse grained heat affected zone,CGHAZ)在服役过程中形成再热裂纹的微观机理,揭示了工程中未热处理T23水冷壁接头在机组启机后,短期运行容易发生开裂泄漏的内在原因.采用材料表征手段对未时效和高温时效处理后的水冷壁焊接接头CGHAZ硬度、微观组织、析出物物相等进行系统分析.结果表明,在 530℃时效 100 h后,CGHAZ硬度出现由晶内弥散强化导致的二次硬化现象,随着时效(运行)时间增加,CGHAZ硬度逐渐降低,但时效 1000 h后,CGHAZ硬度仍有 319 HV高于标准要求;在 600℃温度下,随着时效时间的增加,CGHAZ硬度随之降低,组织回复、再结晶、马氏体板条宽化、位错密度降低、C元素及合金元素从基体析出等因素导致的CGHAZ硬度降低作用高于MX碳化物在晶内弥散析出导致的硬度升高,M23C6 型碳(氮)化物在晶界、亚晶界逐渐析出和长大.
Abstract
The micro-mechanism of reheat crack formation in coarse grain heat affected zone(CGHAZ)of welded joint of T23 water wall tube without heat treatment after welding was analyzed by high temperature aging method.It reveals the in-ternal reason that T23 water wall joint without heat treatment is easy to crack and leak in short-term operation after unit star-tup.The hardness,microstructure and precipitates of welded joints of water wall after unaged and high temperature aging treatment were systematically analyzed by means of material characterization.The results show that after aging at 530℃for 100 h,the hardness of CGHAZ appears secondary hardening caused by intragranular dispersion strengthening.With the in-crease of aging(running)time,the hardness of CGHAZ gradu-ally decreases,but after aging for 1 000 h,the hardness of CGHAZ is still 319 HV,which is higher than the standard re-quirement.After aging at 600℃,the hardness of CGHAZ de-creases with the increase of aging time.The hardness of CGHAZ decreased due to the recovery of microstructure,re-crystallization,broadening of martensite lath,reduction of dis-location density,and precipitation of C and alloy elements from the matrix,which is higher than the hardness increased due to dispersion and precipitation of MX carbide in the grain.M23C6 carbide gradually precipitates and grows at grain boundaries and subgrain boundaries.
关键词
高温时效/T23钢/水冷壁/CGHAZ/再热裂纹Key words
high temperature aging/T23 steel/water cool-ing wall/CGHAZ/reheat crack引用本文复制引用
出版年
2024
NETL
NSTL
维普
万方数据