火电站用T92耐热钢工程服役退化研究
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摘要
为了查明超超临界火力发电机组的高温锅炉管道T92耐热钢在高温长时服役过程中的组织及性能变化情况,通过光学显微观察、扫描电镜、EDS能谱分析、透射电镜分析、显微硬度测试,常规拉伸试验和微型杯突试验,研究了原始态及服役两年和三年的T92钢管的显微组织结构和力学性能的变化规律.试验结果表明:高温服役三年后的T92钢组织上仍然保持马氏体板条形态,析出碳化物的数量和尺寸不断增加,且服役两年及三年后组织中除了原始态时的M23C6和MX相,还在原奥氏体晶界及马氏体板条界处析出大量粗化较快的Laves相.材料室温力学性能随服役时间增加整体呈下降趋势,维氏硬度在服役三年后降低了13%,而其屈服强度,抗拉强度分别下降了5.35%和4.19%.SEM断口形貌分析可知随服役年限的增加,断裂特征由韧性断裂向韧脆混合断裂方式转变.
T92steel has become one of the main candidate alloys for ultra supercritical plants(USC),therefore it is of great necessity to secure the safe service of generator set by exploring the rules behind the microstructure and mechanical property change under the condition of high temperature service.Metallographic microscopy,scanning electron microscopy,EDS analysis,transmission electron microscopy,micro hardness test,conventional tensile test and small punch test are conducted to measure the microstructure and mechanical properties of original state T92steel samples and the ones after two year and three year service.Results show:After three year service,the microstructure of T92steel still remains lath martensite,but the number and size of the main precipitates have increased.Besides precipitates M23C6and MX,which already exist in original T92steel,there is Laves phase particles emerging at the boundary of martensite and austenite in T92steel samples after two year service,and the Laves phase experiences rapidly coarsening under high temperature service.Also,the hardness,yield strength and tensile strength decrease by 13%,5.35% and 4.19%,respectively.Meanwhile,the SEM observation of instantaneous tensile fracture and small punch test fracture shows that the fracture has changed from the ductile fracture to ductile brittle fracture after serving.
T92steel has become one of the main candidate alloys for ultra supercritical plants(USC),therefore it is of great necessity to secure the safe service of generator set by exploring the rules behind the microstructure and mechanical property change under the condition of high temperature service.Metallographic microscopy,scanning electron microscopy,EDS analysis,transmission electron microscopy,micro hardness test,conventional tensile test and small punch test are conducted to measure the microstructure and mechanical properties of original state T92steel samples and the ones after two year and three year service.Results show:After three year service,the microstructure of T92steel still remains lath martensite,but the number and size of the main precipitates have increased.Besides precipitates M23C6and MX,which already exist in original T92steel,there is Laves phase particles emerging at the boundary of martensite and austenite in T92steel samples after two year service,and the Laves phase experiences rapidly coarsening under high temperature service.Also,the hardness,yield strength and tensile strength decrease by 13%,5.35% and 4.19%,respectively.Meanwhile,the SEM observation of instantaneous tensile fracture and small punch test fracture shows that the fracture has changed from the ductile fracture to ductile brittle fracture after serving.
引文
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[3]张红军,周容灿,唐丽英,等.P92钢650℃时效的组织性能研究[J].中国电机工程学报,2009,(29):174.ZHANG Hong-jun,ZHOU Rong-can,TANG Liying,et al.Study on Microstructure and Mechanical Properties of P92 Steel Aged at 650℃[J].Proceedings of the CSEE,2009,(29):174.(in Chinese)
[4]窦洪,王志武,宋涛.服役10500h后超临界锅炉高温再热器用T92钢管的显微组织[J].机械工程材料,2013,37(5):15.DOU Hong,WANG Zhi-wu,SONG Tao.Microstructure of T92Steel Pipe Used for High Temperature Reheater in Supercritical Boiler after Working for 10500h[J].Material for Mechanical Engineering,2013,37(5):15.(in Chinese)
[5]许建豪,赵彦芬,王起江,等.宝钢T92钢管母材性能试验与应用评价[J].宝钢技术,2011,1:29.XJian-hao,ZHAO Yan-fang,WANG Qi-jiang,et al.Property Tests and Application Evaluation of Baosteel T92Steel for High Pressure Boiler Tubes[J].Bao-Steel Technology,2011,1:29.(in Chinese)
[6]要玉宏,刘江南,王正品,等.材料力学性能的微型杯突试验评述[J].理化检验,2004,40(1):29.YAO Yu-hong,LIU Jiang-nan,WANG Zheng-pin,et al.Commentary of Small Punch Test for Material Mechanical Properties[J].Physical Testing,2004,40(1):29.(in Chinese)
[7]窦洪,王志武,宋涛.超超临界机组压力锅炉用T92/P92钢析出相的研究进展[J].广东电力,2012,25(2):15.DOU Hong,WANG Zhi-wu,SONG Tao.Research Progress of Precipitated Phase of T92/P92Steel for Ultra Supercritical Pressure Boilers[J].Guangdon Electric Power,2012,25(2):29.(in Chinese)
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[9]郭晓峰,巩建鸣,姜勇.超超临界锅炉管用T92/P92钢研究进展[J].技术综述,2001,5(28):55.GUO Xiao-feng,GONG Jian-ming,JIANG Yong.Research Advances of T92/P92Steel for Boiler Pipes of USC Power Plants[J].CPVT,2001,5(28):55.(in Chinese)