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http://dx.doi.org/10.3740/MRSK.2018.28.7.391

Microstructure and Tensile Properties of 700 MPa-Grade High-Strength and Seismic Resistant Reinforced Steel Bars  

Hong, Tae-Woon (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
Lee, Sang-In (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
Hwang, Byoungchul (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
Publication Information
Korean Journal of Materials Research / v.28, no.7, 2018 , pp. 391-397 More about this Journal
Abstract
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 ferrite-pearlite, 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.
Keywords
high strength; seismic resistant; reinforced steel bar; microstructure; tensile property;
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