Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Characterization of Aluminum Coated Layer in Hot Press Forming of Boron Steel

고온 프레스성형시 보론강 알루미늄 코팅층 거동특성

  • Jang, Jeong-Hwan (Department of Mechanical and Precision Engineering/Engineering Research Center for Net Shape and Die Manufacturing, Pusan National University) ;
  • Joo, Byeong-Don (Department of Mechanical and Precision Engineering/Engineering Research Center for Net Shape and Die Manufacturing, Pusan National University) ;
  • Lee, Jae-Ho (Department of Mechanical and Precision Engineering/Engineering Research Center for Net Shape and Die Manufacturing, Pusan National University) ;
  • Moo, Young-Hoon (Department of Mechanical and Precision Engineering/Engineering Research Center for Net Shape and Die Manufacturing, Pusan National University)
  • 장정환 (부산대학교 정밀기계공학과/정밀정형 및 금형가공 연구소) ;
  • 주병돈 (부산대학교 정밀기계공학과/정밀정형 및 금형가공 연구소) ;
  • 이재호 (부산대학교 정밀기계공학과/정밀정형 및 금형가공 연구소) ;
  • 문영훈 (부산대학교 정밀기계공학과/정밀정형 및 금형가공 연구소)
  • Received : 2008.06.23
  • Accepted : 2008.07.14
  • Published : 2008.07.31
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Abstract

Hot press forming allows geometrically complicated parts to be formed from sheet and the rapid cooling hardens them to extremely high strength. The main purpose of this research is to characterize Al coated layer in Al coated boron steel during hot press forming. For the hot press hardening experiment, test specimens were heated up to $810{\sim}930^{\circ}C$ and held for 3, 6 and 9 minutes, respectively. And then, some specimens were press hardened and others were air-cooled without any pressing for the comparison purpose. Al coated layer shows four distinct micro-structural regions of interest; diffusion zone, Al-Fe zone(I) low-Al zone(LAZ) and Al-Fe zone(II). Band-like LAZ is clearly shown at temperature ranges of $810{\sim}870^{\circ}C$ and sparsely dispersed at temperature higher than 900oC. The micro-cracking behavior in the Al coated layer during forming were also analyzed by bending and deep drawing tests. The strain concentration in softer LAZ is found to be closely related with micro-cracking and exfoliation in coated layer during forming.

Keywords

References

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