Improvement in Punching Properties of High Tensile Strength Steel Sheet by Heat-Treatments for Reduction of Center Segregation

Abstract:

We investigated punching properties (crack in punched surface and hole expansion ratio) of high tensile strength steel sheets with and without center segregation. High strength steel sheets were heat-treated to reduce center segregation. Tensile strength, shear surface ratio, depth of rollover and burr height were measured on heat-treated steel sheets to confirm the effect of heat-treatment on strength. The EPMA analysis showed that the center segregation of Mn was reduced by the diffusion during heat-treatment. Crack-formation frequency and hole expansion ratio were also measured. As a result, the center segregation of Mn in high tensile strength steel sheets decreased by the heat-treatment (600 ^oC for 100 h) with maintaining the tensile strength, the depth of rollover and the burr height. The crack-formation frequency of the steel sheets decreased through heat-treatments.

• Periodical: Key Engineering Materials (Volumes 622-623)
• Pages: 1075-1080
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.622-623.1075
• Online since: September 2014
• Authors: Kota Sakumoto*, Kazuhiko Yamazaki, Takashi Kobayashi, Shinsuke Suzuki
• Keywords: Center Segregation, High Tensile Steel Sheet, Hole Expansion Ratio, Punching

References

[1] E. Iizuka, T. Hira, A. Yoshitake, Effect of forming conditions on stretch flange formability of high- strength hot-rolled steel sheets, Jpn. Soc. Technol. Plasticity. 46 (2005) 81-85.

[2] T. Matsuno, Y. Kuriyama, H. Murakami, S. Yonezawa, N. Kanamura, Hole Expansion ratio and fatigue properties in piercing of high-strength steel sheets by PW punch, Jpn. Soc. Technol. Plasticity. 52 (2011) 41-46.

DOI: 10.9773/sosei.52.795

[3] K. Mori, S. Saito, S. Maki, Warm and hot punching of ultra high strength steel sheet, CIRP Ann. Manufacturing. Technol. 57 (2008) 321-324.

DOI: 10.1016/j.cirp.2008.03.125

[4] T. Kawawa, H. Sato, S. Miyahara, T. Koyano H. Nemoto, Macro-and micro-structure of continuously cast slab, Tetsu-to-Hagane. 5 (1974) 22-36.

DOI: 10.2355/tetsutohagane1955.60.5_486

[5] K. Osakada, H. Kido, H. Sekiguchi, The anisotropy of ductile in carbon steel, Bulletin of JSNE. 26 (1983) 2067-(2073).

[6] Japanese industrial standards committee, JIS Z 2241 Metallic materials-Tensile testing-Method of test at room temperature, Japanese standards association, Tokyo, (2008).

[7] Japanese industrial standards committee, JIS Z 2256 Metallic materials-Hole expanding test, Japanese standards association, Tokyo, (2010).

[8] K. Yamada, T. Hujita, K. Ogi, Diffusion of centerline segregation in continuous cast bloom by re-heating, ISIJ. Int. 66 (1980) 272.