Effects of Thermal Cycle on Microstructure and Cryogenic Toughness of Coarse-Grained Heat Affected Zone of 9Ni Steel Joint

YANG Xiuzhi; ZHANG Lichao; LI Xuan; HUA Wenlin; YANG Chunjie; DONG Chunfa; XIAO Xinhua

doi:10.11973/jxgccl201808016

Materials and Mechanical Engineering > 2018 > 42(8): 78-82. > DOI: 10.11973/jxgccl201808016

YANG Xiuzhi, ZHANG Lichao, LI Xuan, HUA Wenlin, YANG Chunjie, DONG Chunfa, XIAO Xinhua. Effects of Thermal Cycle on Microstructure and Cryogenic Toughness of Coarse-Grained Heat Affected Zone of 9Ni Steel Joint[J]. Materials and Mechanical Engineering, 2018, 42(8): 78-82. DOI: 10.11973/jxgccl201808016

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Effects of Thermal Cycle on Microstructure and Cryogenic Toughness of Coarse-Grained Heat Affected Zone of 9Ni Steel Joint

1. Mechanical and Electrical Engineering College, Hubei Polytechnic University, Huangshi 435003, China;
2. State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China;
3. Mechanical Engineering College, Wuhan Textile University, Wuhan 430073, China

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Received Date: January 10, 2017
Revised Date: March 02, 2018

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Abstract

Coarse-grained heat affected zone (CGHAZ) samples of 9Ni steel joint were prepared with Gleeble-3500 type thermal simulator at t_8/5 (cooling time from 800℃ to 500℃) of 6,10,30,60,100 s, respectively, and then cryogenic impact tests were carried out on the samples. The effects of t_8/5 on the microstructure and cryogenic toughness of CGHAZ were investigated. The results show that the microstructure of CGHAZ was mainly composed of lath martensite. The granular bainite appeared at t_8/5 of 30 s and the amount increased with increasing t_8/5. With increasing t_8/5, the size of martensite lath in CGHAZ increased slightly and then decreased; the ductile-brittle transition temperature rose and then decreased. The impact energy at -100℃ and -125℃ of CGHAZ prepared at different values of t_8/5 was higher than 200 J. With decreasing impact temperature, the impact fracture morphology changed from dimple to quasi-cleavage.
- 9Ni steel,
- cryogenic toughness,
- welding,
- thermal cycle,
- coarse-grained heat affected zone

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