Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
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Tensile and Charpy Impact Properties of High-Strength Bainitic Steels Fabricated by Controlled Rolling Process

제어압연한 베이나이트계 고강도강의 인장 및 충격 성질

  • 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 : 2010.03.17
  • Published : 2010.07.22
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Abstract

This study is concerned with tensile and Charpy impact properties of high-strength bainitic steels fabricated by controlled rolling process. Six kinds of steels were fabricated by varying finish rolling temperature, start cooling temperature, and cooling rate, and their microstructures and tensile and Charpy impact properties were investigated. Their effective grain sizes were also characterized by the electron backscatter diffraction analysis. The microstructures of the steels rolled in the single phase region were most similar to those of the steels rolled in the two phase region. The steels cooled from $700{^{\circ}C}$ were composed mainly of granular bainites, while those cooled from $600{^{\circ}C}$ contained a number of bainitic ferrites, which resulted in the decrease in ductility and upper shelf energy in spite of the increase in strength. In the steels cooling from $600^{\circ}C$, fine acicular ferrites were well formed when the cooling rate was slow, which led to the best combination of high ductility, high upper shelf energy, and low energy transition temperature according to the decrease in the overall effective grain size due to the presence of acicular ferrites having smaller effective grain size.

Keywords

Acknowledgement

Supported by : 지식경제부

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