Abstract：To study the thermal aging of nuclear primary pipe material 316LN stainless steel weld, accelerated thermal aging experiment was performed at 400℃ for 15000h. Microstructure evolution of weld after aging was investigated by TEM and HREM. Impact properties of weld thermally aged at different time was measured by Charpy impact test. Meanwhile, taking Charpy impact energy as the standard of thermal aging embrittlement, the thermal kinetics formula was obtained by the fitting method. Finally, the Charpy impact properties of the weld during 60 years of service at the actual operation temperature were estimated by the thermal kinetics formula. The results indicate that the spinodal decomposition occurs in the ferrite of the weld after thermal aging at 400℃ for 1000h, results in α (Fe-rich) and α'(Cr-rich) phases, and meanwhile, the G-phase is precipitated in the ferrite; the spinodal decomposition and the G-phase precipitation lead to the decrease in the impact energy of weld as time prolongs; the prediction results show that the Charpy impact energy of weld decreases quickly in the early 25 years, and then undergoes a slow decrease during the subsequent operation process.
罗强, 刘思维, 陈勇, 周军, 何琨. 热老化对316LN不锈钢焊缝微观组织和冲击性能的影响[J]. 材料工程, 2017, 45(12): 25-29.
LUO Qiang, LIU Si-wei, CHEN Yong, ZHOU Jun, HE Kun. Effects of Thermal Aging on Microstructure and Impact Properties of 316LN Stainless Steel Weld. Journal of Materials Engineering, 2017, 45(12): 25-29.
 杨文斗.反应堆材料学[M].北京:原子能出版社,2009. YANG W D.Reactor materials[M].Beijing:Atomic Energy Press,2009.
 王永强,李娜,杨滨,等.核电管道不锈钢中σ相的退火消除及脆性恢复[J].材料工程,2016,44(5):29-36. WANG Y Q, LI N, YANG B,et al.Annealing induced removing of σ phase and recovery of embrittlement in stainless steel used for nuclear power plant pipes[J]. Journal of Materials Engineering, 2016,44(5):29-36.
 郎宇平,陈海涛,翁宇庆,等.热力学计算在高氮奥氏体不锈钢研究中的应用[J].材料工程,2013(5):16-22. LANG Y P,CHEN H T,WENG Y Q,et al.Applications of Thermo-Calc in research of high nitrogen austenitic stainless steels[J].Journal of Materials Engineering,2013(5):16-22.
 CHOPRA O K,AYRAULT G.Aging degradation of cast stainless steel:status and program[J].Nuclear Engineering and Design,1985,86(1):69-77.
 GOTO T,NAITO T,YAMAOKA T.A study on NDE method of thermal aging of cast duplex stainless steels[J].Nuclear Engi-neering and Design,1998,182(2):181-192.
 YAMADA T,OKANO S,KUWANO H.Mechanical property and microstructural change by thermal aging of SCS14A cast duplex stainless steel[J].Journal of Nuclear Materials,2006,350(1):47-55.
 王明家,马千,李景丽,等.热老化对核级316LN锻造控氮奥氏体不锈钢微观组织及性能的影响[J].燕山大学学报,2013,37(5):385-388. WANG M J,MA Q,LI J L,et al.Influence of thermal aging on microstructure and mechanical properties of nuclear grade 316LN forged austenitic stainless steel[J].Journal of Yanshan University,2013,37(5):385-388.
 李时磊,王艳丽,李树肖,等.长期热老化对铸造奥氏体不锈钢组织和性能的影响[J].金属学报,2000,46(10):1186-1191. LI S L,WANG Y L,LI S X,et al.Effect of long term aging on the microstructure and mechanical properties of cast austenitic stainless steels[J].Acta Metallurgica Sinica,2000,46(10):1186-1191.
 CHANDRA K,KAIN V,RAJA V S,et al.Low temperature thermal ageing embrittlement of austenitic stainless steel welds and its electrochemical assessment[J].Corrosion Science,2012,54:278-290.
 CHANDRA K,KAIN V,BHUTANI V.Low temperature thermal aging of austenitic stainless steel welds:kinetics and effects on mechanical properties[J].Materials Science and Engineering:A,2012,534:163-175.
 郑凯,王艳丽,李时磊,等.长期热老化后Z3CN20-09M不锈钢的微观组织与拉伸断裂行为[J].金属学报,2013,49(2):175-180. ZHENG K,WANG Y L,LI S L,et al.The microstructure and tensile fracture behavior of long term thermal aged Z3CN20-09M stainless steel[J].Acta Metallurgica Sinica,2013,49(2):175-180.
 PUMPHREY P H,AKHURST K N.Aging kinetics of CF3 cast stainless steel in temperature range 300-400℃[J].Materials Science and Technology,1990,6(3):211-220.
 PAREIGE C,NOVY S,SAILLET S,et al.Study of phase transformation and mechanical properties evolution of duplex stainless steels after long term thermal ageing(>20 years)[J].Journal of Nuclear Materials,2011,411(1/3):90-96.
 BAEK S,KOO J M,SEOK C S.Evaluation of the degradation characteristics of CF-8A cast stainless steel using indentation techniques and EDS[J].Key Engineering Materials,2006,306/308:869-874.