Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
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Effects of Alloying Elements and the Cooling Condition on the Microstructure, Tensile Properties, and Charpy Impact Properties of High-Strength Bainitic Steels

베이나이트계 고강도강의 합금원소와 냉각조건이 미세조직, 인장성질, 충격성질에 미치는 영향

  • Sung, Hyo Kyung (Center for Advanced Aerospace Materials, Pohang University of Science and Technology) ;
  • Shin, Sang Yong (Center for Advanced Aerospace Materials, Pohang University of Science and Technology) ;
  • Hwang, Byoungchul (Ferrous Alloys Research Group, Korea Institute of Materials Science) ;
  • Lee, Chang Gil (Ferrous Alloys Research Group, Korea Institute of Materials Science) ;
  • Kim, Nack J. (Graduate Institute of Ferrous Technology, Pohang University of Science and Technology) ;
  • Lee, Sunghak (Center for Advanced Aerospace Materials, Pohang University of Science and Technology)
  • 성효경 (포항공과대학교 항공재료연구센터) ;
  • 신상용 (포항공과대학교 항공재료연구센터) ;
  • 황병철 (한국기계연구원 부설 재료연구소 철강재료연구그룹) ;
  • 이창길 (한국기계연구원 부설 재료연구소 철강재료연구그룹) ;
  • 김낙준 (포항공과대학교 철강대학원) ;
  • 이성학 (포항공과대학교 항공재료연구센터)
  • Received : 2010.05.10
  • Published : 2010.09.22
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Abstract

The effects of alloying elements and the cooling condition on the microstructure, tensile properties, and Charpy impact properties of high-strength bainitic steel plates fabricated by a controlled rolling process were investigated in the present study. Eight kinds of steel plates were fabricated by varying C, Cr, and Nb additions under two different cooling rates, and their microstructures and tensile and Charpy impact properties were evaluated. The microstructures present in the steels increased in the order of granular bainite, acicular ferrite, bainitic ferrite, and martensite as the carbon equivalent or cooling rate increased, which resulted in a decrease in the ductility and Charpy absorbed energy. The steels containing a considerable amount of bainitic ferrite or martensite showed very high strengths, together with good ductility and Charpy absorbed energy. In order to achieve the best combination of strength, ductility, and Charpy absorbed energy, granular bainite and acicular ferrite were properly included in the high-strength bainitic steels by controlling the carbon equivalent and cooling rate, while about 50 vol.% of bainitic ferrite or martensite was maintained to maintain the high strength.

Keywords

Acknowledgement

Supported by : 지식경제부

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