Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
권호 표지

Effect of Effective Grain Size on Charpy Impact Properties of High-Strength Bainitic Steels

베이나이트계 고강도강의 샤르피 충격 특성에 미치는 유효결정립도 영향

  • Shin, Sang Yong (Center for Advanced Aerospace Materials Pohang University of Science and Technology) ;
  • Han, Seung Youb (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) ;
  • Lee, Sunghak (Center for Advanced Aerospace Materials Pohang University of Science and Technology)
  • 신상용 (포항공과대학교 항공재료연구센터) ;
  • 한승엽 (포항공과대학교 항공재료연구센터) ;
  • 황병철 (한국기계연구원 부설 재료연구소 철강재료연구그룹) ;
  • 이창길 (한국기계연구원 부설 재료연구소 철강재료연구그룹) ;
  • 이성학 (포항공과대학교 항공재료연구센터)
  • Received : 2008.07.10
  • Published : 2008.10.25
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Abstract

This study is concerned with the effect of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels. Six kinds of steels were fabricated by varying alloying elements and hot-rolling conditions, and their microstructures and tensile and Charpy impact properties were investigated. Their effective grain sizes were also characterized by the electron back-scatter diffraction analysis. The tensile test results indicated that the B- or Cu-containing steels had the higher yield and tensile strengths than the B- or Cu-free steels because their volume fractions of bainitic ferrite and martensite were quite high. The B- or Cu-free steels had the higher upper shelf energy than the B- or Cu-containing steels because of their higher volume fraction of granular bainite. In the steel containing 10 ppm B without Cu, the best combination of high strengths, high upper shelf energy, and low energy transition temperature could be obtained by the decrease in the overall effective grain size due to the presence of bainitic ferrite having smaller effective grain size.

Keywords

Acknowledgement

Supported by : 지식경제부, 한국과학재단

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