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金属学报  2018, Vol. 54 Issue (4): 501-511    DOI: 10.11900/0412.1961.2017.00331
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一种Fe-Cr-Ni-Mo高强钢焊接热影响区的显微组织与冲击韧性研究
文明月1,2, 董文超1, 庞辉勇3, 陆善平1()
1 中国科学院金属研究所中国科学院核用材料与安全评价重点实验室 沈阳 110016
2 中国科学技术大学材料科学与工程学院 沈阳 110016
3 舞阳钢铁有限责任公司 平顶山 462500
Microstructure and Impact Toughness of Welding Heat-Affected Zones of a Fe-Cr-Ni-Mo High Strength Steel
Mingyue WEN1,2, Wenchao DONG1, Huiyong PANG3, Shanping LU1()
1 Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
2 School of Materials Science and Engineering, University of Science and Technology of China,Shenyang 110016, China
3 Wuyang Iron and Steel Co. Ltd., Pingdingshan 462500, China
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摘要: 

研究了一种Fe-Cr-Ni-Mo高强钢经不同峰值温度(Tp) (760、830、1020和1320 ℃)焊接热循环后的显微组织与冲击韧性。结果表明,随着Tp的升高,特征热影响区的平均冲击功先增大后减小。粗晶区(CGHAZ,Tp=1320 ℃)和细晶区(FGHAZ,Tp=1020 ℃)的显微组织为淬火马氏体。由于晶粒粗大,造成CGHAZ冲击韧性较差,低于晶粒细小的FGHAZ冲击韧性。部分相变区(ICHAZ,Tp=760 ℃和Tp=830 ℃)的显微组织为淬火马氏体和回火马氏体组成的混合组织,由于冲击试样V型缺口处的混合组织界面所占比例具有随机性,造成ICHAZ冲击功波动较大。ICHAZ (Tp=830 ℃)中均匀的细晶组织对冲击裂纹具有止裂作用,使得该微区具有最佳的冲击性能。尽管ICHAZ (Tp=760 ℃)晶粒细小,但存在的极细晶组织(尺寸为1~2 μm)在遭受冲击载荷时易形成密集分布的次生微孔,基体中未溶的M2C及MC析出相促使微孔连接形成裂纹,导致该微区冲击韧性最差,成为热影响区的薄弱区域。

关键词 Fe-Cr-Ni-Mo高强钢焊接热影响区冲击韧性显微组织    
Abstract

Marine engineering steel is the key material for the construction of major marine infrastructure projects. Due to the harsh environment in the deep sea, the mechanical properties such as strength, low temperature toughness and so on of the marine steel are required to be higher. In this work, the weldability of a Fe-Cr-Ni-Mo high-strength steel was studied, and the microstructure and impact toughness of the steel after welding thermal cycling at different peak temperatures were analyzed. The results show that the average impact toughness of characteristic heat affected zone under different temperatures increases first and then decreases with the increase of peak temperature (Tp). The microstructures of coarse grain heat-affected zone (CGHAZ, Tp=1320 ℃) and fine grain heat-affected zone (FGHAZ, Tp=1020 ℃) are quenched martensite. Because of the coarse grain size, the impact toughness of CGHAZ is poor, which is lower than that of FGHAZ. The microstructure of inter-critical heat-affected zone (ICHAZ, Tp=830 ℃ and Tp=760 ℃) is composed of quenched martensite and tempered martensite. Due to the randomness of the proportion of the interfaces between the mixed microstructures near the V-notch, the impact energy values of ICHAZ fluctuates greatly. The homogeneous fine grain structure in ICHAZ (Tp=830 ℃) has a crack arrest effect during the impact deformation, which makes the characteristic zone have the best impact toughness. Although the grain size in ICHAZ (Tp=760 ℃) is also fine, the existence of the ultra-fine grain zones (the grain size in which is only 1~2 μm) benefits the formation of secondary voids under the impact load. The undissolved M2C and MC precipitations in matrix promote the connecting of secondary voids and then form the secondary cracks. As a result, the impact toughness of the characteristic zone is poor, and becomes the weak region of HAZ.

Key wordsFe-Cr-Ni-Mo high strength steel    welding heat affected zone    impact toughness    microstructure
收稿日期: 2017-08-02      出版日期: 2017-12-12
ZTFLH:  TG401  
基金资助:国家重点研发计划项目No.2016YFB0300601和中国科学院重点部署项目No.GFZD-125-15-003-1
作者简介:

作者简介 文明月,女,1992年生,硕士生

引用本文:

文明月, 董文超, 庞辉勇, 陆善平. 一种Fe-Cr-Ni-Mo高强钢焊接热影响区的显微组织与冲击韧性研究[J]. 金属学报, 2018, 54(4): 501-511.
Mingyue WEN, Wenchao DONG, Huiyong PANG, Shanping LU. Microstructure and Impact Toughness of Welding Heat-Affected Zones of a Fe-Cr-Ni-Mo High Strength Steel. Acta Metall Sin, 2018, 54(4): 501-511.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2017.00331      或      http://www.ams.org.cn/CN/Y2018/V54/I4/501

图1  HAZ各微区的特征热循环曲线
图2  HAZ各微区在不同温度下的Charpy-V型缺口冲击功
图3  0 ℃下ICHAZ的示波冲击载荷-位移曲线
Tp / ℃ Sample No. Ei / J Ep / J Et / J
760 1 30 39 69
2 22 27 49
3 15 24 39
830 1 45 67 112
2 42 52 94
3 44 35 79
表1  ICHAZ在0 ℃下示波冲击实验的裂纹起裂功Ei、裂纹扩展功Ep及总冲击功Et
图4  焊接状态下加热速率与奥氏体转变温度A1和A3的关系
图5  HAZ各微区的显微组织与原奥氏体晶界形貌的OM像
图6  HAZ各微区的SEM像
Tp / ℃ Quenched martensite Tempered martensite
830 594 448
760 574 472
表2  ICHAZ中不同显微组织的硬度
图7  ICHAZ (Tp=760℃)的EBSD像
图8  -20 ℃下ICHAZ冲击样品断口纵剖面上的二次裂纹分布
图9  ICHAZ冲击样品中2种二次裂纹所占比例与冲击功的关系
图10  ICHAZ冲击断口形貌
图11  ICHAZ的TEM明场像
图12  HAADF-STEM模式下,ICHAZ (Tp=760℃)的TEM像及M2C相和MC相的SAED谱
图13  ICHAZ中次生微孔生长过程示意图
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