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http://dx.doi.org/10.12656/jksht.2015.28.2.75

Effects of B and Cu Additions on the Microstructure and Mechanical Properties of High-Strength Bainitic Steels  

Yim, H.S. (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
Lee, S.Y. (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
Hwang, B. (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
Publication Information
Journal of the Korean Society for Heat Treatment / v.28, no.2, 2015 , pp. 75-81 More about this Journal
Abstract
Effects of B and Cu additions on the microstructure and mechanical properties of high-strength bainitic steels were investigated in this study. Six kinds of high-strength bainitic steels with different B and Cu contents were fabricated by thermo-mechanical control process composed of controlled rolling and accelerated cooling. The microstructures of the steels were analyzed using optical and transmission microscopy, and the tensile and impact tests were conducted on them in order to investigate the correlation of microstructure with mechanical properties. Depending on the addition of B and Cu, various low-temperature transformation products such as GB (granular bainite), DUB (degenerated upper bainite), LB (lower bainite), and LM (lath martensite) were formed in the steels. The addition of B and Cu increased the yield and tensile strengths because of improved hardenability and solid solution strengthening, but decreased the ductility and low-temperature toughness. The steels containing both B and Cu had a very high strength above 1.0 GPa, but showed a worse low-temperature toughness of higher DBTT (ductile-to-brittle transition temperature) and lower absorbed energy. On the other hand, the steels having GB and DUB showed a good combination of tensile and impact properties in terms of strength, ductility, yield ratio, absorbed energy, and DBTT.
Keywords
Bainitic steel; High-Strength; Microstructure; Mechanical properties; B; Cu;
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  • Reference
1 T. Hayashi, F. Kawabata and K. Amano : Proc. Materials Solution 97 on Accerated Cooling/Direct Quenching Steels, ASM, Materials Parks, OH, 1997, pp. 93-99.
2 J. Koo, M. J. Luton, N. V. Bangaru, R. A. Petkovic, D. P. Fairchild, C. W. Petersen, H. Asahi, T. Hara, Y. Terada, M. Sugiyama, H. Tamehiro, Y. Komizo, S. Okaguchi, M. Hamada, A. Yamamoto and I. Takeuchi : Int. J. Offshore and Polar Eng. 14 (2004) 2.
3 B. Hwang, C. G. Lee, S. Lee and C. Lee : Trends in Metals & Materials Engineering (The Korean Institute of Metals and Materials), 22 (2009) 28.
4 H. K. Sung, S. Y. Shin, B. Hwang, C. G. Lee and S. Lee : Metall. Mater. Trans. 44A (2013) 294.
5 H. K. Sung, D. H. Lee, S. Y. Shin, S. Lee, J. Y. Yoo and B. Hwang : Mater. Sci. Eng. A624 (2015) 14.
6 D. H. Werner : Boron and Boron Containing Steels, Verlag Stahleisen mbH, Dusseldorf, 1995.
7 B. Hwang, D. W. Suh and S. J. Kim : Scripta Mater. 64 (2011) 1118.   DOI   ScienceOn
8 H. K. Sung, S. Y. Shin, B. Hwang, C. G. Lee and S. Lee : Metall. Mater. Trans. 43A (2012) 3703.
9 S. Takaki, M. Fujioka, S. Aihara, Y. Nagtataki, T. Yamashita, N. Sano, Y. Adachi, M. Nomura and H. Yaguchi : Mater. Trans. JIM, 45 (2004) 2239.   DOI
10 A. M. Elwazri, A. Fatehi, J. Calvo, D. Bai and S. Yue : ISIJ Int., 48 (2008) 107.   DOI
11 I. Tamura, H. Sekine, T. Tanaka and C. Ouchi : Thermomechanical Processing of High-Strength Low-Alloy Steels, Butterworth & Co. Ltd., London, 1988.
12 R. W. Hertzberg : Deformation and Fracture Mechanics of Engineering Materials, 4th ed., John Wiley & Sons, Inc., 1996.
13 T. Gladman : The Physical Metallurgy of Microalloyed Steels, The Institute of Materials, London, 1997.