Abstract Gas tungsten arc welding (GTAW) joints of nuclear power main pipelines were subjected on accelerated thermal ageing tests until 30000 h to investigate long-term ageing effect on fracture property. The results indicate that fracture toughness values JIC and JSZW of both base metals and welded metals decreases clearly and fracture mode transits subsequently from typical ductile to brittle fracture with increasing ageing time, but J-resistance (J-R) curves still lie above the recommend low-bound lines given by NUREG/CR after 30000 h thermal ageing. Moreover, base metals have better fracture toughness than welded metals regardless of thermal ageing time, and thus welded metals are still the weakest part for the whole welded joints. In addition, thermal ageing has no significantly influence on the location of crack initiation at the crack tip and crack growth mode because the thermal ageing could enhance the hardness and strength of ferrite phases and thus the austenite phases still have lower strength.

中文翻译：

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长期时效对核电主管道GTAW焊接接头断裂韧性的影响

摘要 对核电主管道钨极气体保护焊（GTAW）接头进行了30000 h的加速热老化试验，研究了长期老化对断裂性能的影响。结果表明，随着时效时间的增加，母材和焊接金属的断裂韧性值 JIC 和 JSZW 均明显下降，断裂模式随后从典型的韧性断裂转变为脆性断裂，但 J 电阻 (JR) 曲线仍高于推荐的低- NUREG/CR 在 30000 小时热老化后给出的边界线。而且，无论热时效时间如何，母材都比焊接金属具有更好的断裂韧性，因此焊接金属仍然是整个焊接接头中最薄弱的部分。此外，