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http://dx.doi.org/10.3365/KJMM.2018.56.11.796

Impact Toughness and Softening of the Heat Affected Zone of High Heat Input Welded 390 MPa Yield Strength Grade TMCP Steel  

Bang, Kook-Soo (Dept. of Materials System Eng., Pukyong National University)
Ahn, Young-Ho (Technical Research Laboratories, POSCO)
Jeong, Hong-Chul (Technical Research Laboratories, POSCO)
Publication Information
Korean Journal of Metals and Materials / v.56, no.11, 2018 , pp. 796-804 More about this Journal
Abstract
The Charpy impact toughness of the heat affected zone (HAZ) of electro gas welded 390 MPa yield strength grade steel, manufactured by a thermo mechanically controlled process, was investigated. The effects of added Nb on the toughness of the steel and the factors influencing scatter in toughness are discussed in the present work. It was observed that adding Nb to the steel led to the deterioration of HAZ toughness. The presence of soluble Nb in the HAZ increased its hardenability and resulted in a larger amount of low toughness bainitic microstructure. Microstructural observations in the notch root area revealed the significant role of different microstructures in the area. In the presence of a larger amount of bainitic microstructures, the HAZ exhibited a lower Charpy toughness with a larger scatter in toughness. A softened zone with a lower hardness than the base metal was formed in the HAZ. However, theoretical analysis revealed that the presence of the zone might not be a problem in a real welded joint because of the plastic restraint effect enforced by surrounding materials.
Keywords
alloys; welding; toughness; impact test; niobium;
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  • Reference
1 W.-H. Choi, S.-K. Cho, W.-K. Choi, S.-G. Ko, and J.-M. Han, J. Kor. Weld. Join. Soc. 30, 64 (2012).
2 H.-D. Jeong, Y.-H. Park, Y.-H. Ahn, and J.-B. Lee, J. Kor. Weld. Join. Soc. 25, 57 (2007).
3 K. Sasaki, K. Suda, R, Motomatsu, Y. Hashiba, S. Ohkita, and S. Imai, Nippon Steel Tech. Rep. 90, 67 (2004).
4 K. Nakashima, K. Hase, and T. Eto, JFE Tech. Rep. 20, 8 (2015).
5 N. Hannerz, Weld. J. 54, 162-s (1975).
6 H. Song, G. Evans, and S. Babu, Sci. Tech.Weld. Join. 19, 376 (2014).   DOI
7 H. Bhadeshia and A. Sugden, Proc. Int. Conf. on Recent Trends in Weld. Sci. Tech. (eds. S. David and J. Vitek), p. 745, ASM Int., Gatlinburg, USA (1989).
8 S. Matsuda, S. Sekiguchi, and H. Kageyama, Tetsu-to- Hagane. 64, 1209 (1978).   DOI
9 JPVRC Rep. MPS-3, Sept. (1983).
10 S. Graham, J. Test. Eval. 33, 550 (2005).
11 N. Bailey, Proc. 2nd Int. Conf. on Trends in Weld. Res. (eds. S. David and J. Vitek), p. 110, ASM Int., Gatlinburg, USA (1991).
12 K.-S. Bang and S.-W. Jung, J. Kor. Weld. Join. Soc. 18, 83 (2000).
13 O. Akselsen, G. Rorvik, M. Onsoien, and O. Grong, Weld. J. 68, 356-s (1989).
14 H. Nitoh, D. Sakai, H. Yajima, Y. Inoue, Y. Sogo, K. Satoh, and M. Toyoda, J. Soc. Naval Arch. Jap. 157, 304 (1988).
15 K. Satoh and M. Toyoda, J. Jap. Weld. Soc. 40, 885 (1971).   DOI
16 K. Satoh, T. Doi, and M. Toyoda, J. Jap. Weld. Soc. 37, 1214 (1968).   DOI