소성∙가공 (Transactions of Materials Processing)

  • 제27권5호
  • /
  • Pages.281-288
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  • 2018
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  • 1225-696X(pISSN)
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  • 2287-6359(eISSN)
한국소성∙가공학회 (The Korean Society for Technology of Plasticity and materials processing)
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내진용 600 및 700 MPa 급 고강도 철근의 미세조직과 인장 특성 비교

Comparative Study of Microstructure and Tensile Properties of 600 and 700 MPa-Grade High-Strength Seismic Resistant Reinforced Steel Bars

  • 홍태운 (서울과학기술대학교 신소재공학과) ;
  • 이상인 (서울과학기술대학교 신소재공학과) ;
  • 이준호 (고려대학교 신소재공학과) ;
  • 심재혁 (한국과학기술연구원 고온에너지연구센터) ;
  • 이명규 (서울대학교 재료공학부) ;
  • 황병철 (서울과학기술대학교 신소재공학과)
  • 투고 : 2018.07.04
  • 심사 : 2018.08.06
  • 발행 : 2018.10.01
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초록

This study deals with the microstructure and tensile properties of 600 and 700 MPa-grade high-strength seismic reinforced steel bars. High-strength seismic resistant reinforced steel bars (SD 600S and SD 700S) were fabricated by TempCore process, especially the SD 700S specimen was more rapid cooled than the SD 600S specimen during the TempCore process. Although two specimens had microstructure of tempered martensite in the surface region, the SD 600S specimen had ferrite-degenerated pearlite in the center region, whereas the SD 700S specimen had bainite-ferrite-degenerated pearlite in the center region. Therefore, their hardness was highest in the surface region and revealed a tendency to decrease from the surface region to the center region because tempered martensite has higher hardness than ferrite-degenerated pearlite or bainite. The SD 700S specimen revealed higher hardness in the center region than SD 600S specimen because it contained a larger amount of bainite as well as ferrite-degenerated pearlite. On the other hand, tensile test results indicated the SD 600S and SD 700S specimens revealed continuous yielding behavior because of formation of degenerated pearlite or bainite in the center region. The SD 600S specimen had a little higher tensile-to-yield ratio because the presence of ferrite and degenerated pearlite in the center region and the lower fraction of tempered martensite enhance work hardening.

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참고문헌

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