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Super 304H钢焊接接头时效脆化机理
李新梅1, 邹勇1, 邹增大1, 张忠文2
1.山东大学材料液态结构及遗传性教育部重点实验室, 济南 250061;2.山东电力研究院, 济南 250002
摘要:
采用扫描电镜、能谱仪、透射电镜、X射线衍射分析等方法并通过冲击试验,研究了Super 304H钢接头在650℃时效后的脆化现象.试验发现,接头的组织为γ+析出相,造成接头650℃时效脆化的根本原因是焊缝金属中大量Cr23C6沿晶析出,而且析出量是决定因素.经650℃时效后,组织中均明显析出Nb(C,N)和Cr23C6,并最终达到相对稳定的数量,其中随晶界上Cr23C6数量快速增加,晶界急剧脆化;其断裂形式逐步向沿晶断裂转变,导致接头冲击吸收功显著降低,尤其是焊缝金属因沿枝晶界析出Cr23C6引起基体严重脆化,而在焊接条件下接头各部位韧度主要与基体的组织形态有关.
关键词:  时效  奥氏体钢  焊接接头  脆化
DOI:
分类号:
基金项目:山东电力集团公司重点科技基金资助项目(2007A-47);山东省自然科学基金资助项目(Z2006F07)
Aging embrittlement of Super 304H steel welded joint
LI Xinmei1, ZOU Yong1, ZOU Zengda1, ZHANG Zhongwen2
1.Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061, China;2.Shandong Electric Power Research Institute, Jinan 250002, China
Abstract:
The embrittlement of welded joints of Super 304H steel was investigated by means of scanning electron microscopy,energy dispersive spectroscopy,transmission electron microscopy,X-ray diffraction analysis and the impact test.The experimental results indicate that the microstructure of welded joints consists of γ-matrix and precipitated phase.The reason of embrittlement of welded joint is that Cr23C6 precipitated alone coarse grain boundary and the amount of precipitation are the key factors.After being aged at 650 ℃,there are obvious precipitated Nb(C,N) and Cr23C6 phases in welded joint,and the amount of precipitate reaches a stable value with the increasing of aging time;the precipitation of Cr23C6 causes the intergranular embrittlement of welded seam,the impact energy of welded joint reduces rapidly,and the fracture mode turns to intergranular fracture.The toughness of welded joint of Super 304H steel depends on the microstructure of the matrix under welded condition.
Key words:  aging treatment  austenitic steel  welded joint  embrittlement