Korean Journal of Materials Research, Vol.28, No.7, 391-397, July, 2018
700 MPa급 고강도 및 내진 철근의 미세조직과 인장 특성
Microstructure and Tensile Properties of 700 MPa-Grade High-Strength and Seismic Resistant Reinforced Steel Bars
This study deals with the microstructure and tensile properties of 700 MPa-grade high-strength and seismic reinforced steel bars. The high-strength reinforced steel bars (600 D13, 600 D16 and 700 D13 specimens) are fabricated by a TempCore process, while the seismic reinforced steel bar (600S D16 specimen) is fabricated by air cooling after hot rolling. For specimens fabricated by the TempCore process, the 600 D13 and 600 D16 specimens have a microstructure of tempered martensite in the surface region and ferrite-pearlite in the center region, while the 700 D13 specimen has a microstructure of tempered martensite in the surface region and bainite in the center region. Therefore, their hardness is the highest in the surface region and shows a tendency to decrease from the surface region to the center region because tempered martensite has a higher hardness than ferrite-pearlite or bainite. However, the hardness of the 600S D16 specimen, which is composed of fully ferritepearlite, increases from the surface region to the center region because the pearlite volume fraction increases from the surface region to the center region. On the other hand, the tensile test results indicate that only the 700 D13 specimen with a higher carbon content exhibits continuous yielding behavior due to the formation of bainite in the center region. The 600S D16 specimen has the highest tensile-to-yield ratio because the presence of ferrite-pearlite and precipitates caused by vanadium addition largely enhances work hardening.
- KS D 3504, Steel bars for concrete reinforcement, Korean Agency for Technology and Standards (2016).
- Hwang B, Shim JH, Lee MG, Lee J, Jung JH, Kim BS, Won SB, Korean J. Met. Mater., 54, 862 (2016)
- Lee SY, Lee HC, Park CS, Woo KM, Suh YT, J. Korea Concr. Inst., 22, 5 (2010)
- Nikolaou J, Papadimitriou GD, Constr. Build. Mater., 18, 243 (2004)
- Simon P, Economopoulos M, Nilles P, Iron Steel Eng., 61, 53 (1984)
- Jeong GC, J. Korean Soc. Heat Treatment., 2, 47 (1989)
- Li MV, Niebuhr DV, Meekisho LL, Atteridge DG, Metall. Mater. Trans. B-Proc. Metall. Mater. Proc. Sci., 29, 661 (1998)
- Grange RA, Hribal CR, Porter LF, Mater. Trans. A, 8, 1775 (1977)
- Ollilainen V, Kasprzak W, Holappa L, J. Mater. Process. Technol., 134, 405 (2003)
- Marder AR, Bramfitt BL, Metall. Mater. Trans. A-Phys. Metall. Mater. Sci., 7, 365 (1976)
- Hui W, Zhang Y, Shao C, Chen S, Zhao X, Dong H, J. Mater. Sci. Techol., 32, 545 (2016)
- Dieter GE, Mechanical Metallurgy, McGraw-Hill (1988).
- Waterschoot T, De AK, Vandeputte S, De Cooman BC, Metall. Mater. Trans. A-Phys. Metall. Mater. Sci., 34, 781 (2003)
- Kumar A, Singh SB, Ray KK, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 474, 270 (2008)
- Simon P, Economopoulos M, Nilles P, Metall. Plant Tech., 84, 80 (1984)
- Karlsson B, Linden G, Mater. Sci. Eng., 17, 209 (1975)
- Waterschoot T, Cooman BCD, Ke AK, Vandequtte S, Metall. Mater. Trans. A-Phys. Metall. Mater. Sci., 34, 781 (2003)
- Hansen SS, Sande JBV, Cohen M, Metall. Mater. Trans. A-Phys. Metall. Mater. Sci., 11, 387 (1980)
- Shim J, Hwang B, Lee M, Lee J, Calphad, 62, 67 (2018)