• Title, Summary, Keyword: Ferrite-Bainite Duplex Steel

Search Result 4, Processing Time 0.024 seconds

Hole Flangeability and Fracture Behaviors of Circular Flanges of High Strength Hot Rolled Steels (고강도 열연재의 Hole Flanging시 성형특성과 파단에 관한 연구)

  • Kim J. W.;Gong S. R.;Kim B. J.;Moon Y. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • /
    • pp.49-52
    • /
    • 2000
  • The hole flanging experiments are performed on a flat circular plates with a hole in the center and the flangeability and fracture behavior of TRIP steel and ferrite-bainite duplex steel were examined. Over the ranges of conditions investigated, the flangeability of ferrite-bainite duplex steel is better than TRIP steel and the term 'hole flanging capacity' introduced in this study. Fracture behavior of TRIP steel and ferrite-bainite duplex steel was characterized by petal formation at the edge of flange. In case of crack propagation, crack tip diversion that is supposed to be responsible for flangeability occurs more severely on HSLA Steel.

  • PDF

Effect of Lip Shape on the Hole Flangeability of High Strength Steel Sheets (고강도 열연재의 홀 플랜징시 립 형상이 플랜정성에 미치는 효과)

  • Kim, Jeong-Un;Kim, Bong-Jun;Mun, Yeong-Hun
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.26 no.1
    • /
    • pp.147-152
    • /
    • 2002
  • Effect of lip shape on the hole flangeability of high strength steel sheets is investigated. Circular plates of various hole sizes are tested and the variation of lip length as well as the variation of thickness on the sectional views of the finished lip were studied. The conventional hole flanging process is limited to a certain limit hole diameter below which failure will ensue during the hole expansion. The intention of this work is to examine the effect of lip shape on the flangeability of TRIP steel and Ferrite-Bainite duplex steel and find out major parameters which can affect flanging shape of high strength hot rolled steels. Over the ranges of conditions investigated, the minimum hole diameter of F+B steel is better than TRIP steel. while, the lip-shape accuracy of TRIP steel is better than that of F+B steel. although the tensile strength and elongation of %P steel are superior than those of Ferrite-Bainite duplex steel, the flangeability is found to be not so strongly sensitive to the tensile properties but sensitive to displacement on the circumferential direction of hole edge.

A Study on the Stretch-flangeability of Hot-Rolled High Strength Steel with Ferrite-Bainite Duplex Microstructure (페라이트-베이나이트 복합조직 고강도 열연강판의 신장플랜지 특성에 관한 연구)

  • Cho, Yeol-Rae;Chung, Jin-Hwan;Koo, Hwang-Hoe;Kim, In-Bae
    • Korean Journal of Materials Research
    • /
    • v.9 no.12
    • /
    • pp.1252-1262
    • /
    • 1999
  • The effect of microstructures on the strength-flangeability of Nb bearing hot-rolled high strength steel was investigated in order to improve the strength-flangeability of conventional TS 580MPa grades HSLA steel for the automotive wheel disc. The low temperature coiling method using 3-step controlled cooling pattern after hot rolling was effective to produce the Nb-bearing high strength steel with the polygonal ferrite and bainite duplex microstructures. It was suggested that the suppressed precipitation of grain boundary cementites and the decreased hardness difference between ferrite matrix and bainite cause the excellent stretch-flangeability of ferrite-bainite duplex microstructure steel. Therefore, the formation and propagation of microcracks were suppressed relative to the conventional HSLA steel with ferrite and pearlite microstructure. In addition, the elongation was improved as compared with that of hot-rolled steel sheets using conventional early cooling pattern because the volume fraction of polygonal ferrite was increased.

  • PDF

Fracture Analysis of Hole Flanging Process for High Strength Steel Sheets (고강도 열연판재의 홀 플랜정시 파단특성연구)

  • 김정운;김봉준;문영훈
    • Transactions of Materials Processing
    • /
    • v.10 no.6
    • /
    • pp.465-470
    • /
    • 2001
  • Hole flanging experiments are performed on flat circular plates with a hole in the center and the flangeability and fracture behaviors of TRIP steels and ferrite-Bainite duplex steels were examined. In the hole flanging, deformation by lip and petalling occurs when plates are struck by punches of various shapes and high circumferential strains induced in the target material cause radial cracking and the subsequent rotation of the affected plate material in a number of symmetric petals. In all cases, failure of the plate was due to lip fracture that results from multiple localized neckings that take place around the hole periphery where straining is most severe and a somewhat regular pattern was observed in a fracture shape. The neck characteristics in flange formation and the transition from the lip to petal mode at which fracture occurs were compared with two materials.

  • PDF