Metals and Materials

, Volume 5, Issue 6, pp 571–578 | Cite as

Effect of controlled cooling on the formability of TS 590 MPa grade hot-rolled high strength steels

  • Yeol-Rae Cho
  • Jin-Hwan Chung
  • Hwang-Hoe Ku
  • In-Bae Kim


The effect of cooling on the mechanical properties of hot-rolled high strength steels was investigated in order to improve the stretch-flangeability of conventional TS 590 MPa grade for the automotive parts through laboratory simulation and mill-scale production. The low temperature coiling method using a 3-step controlled cooling pattern after hot rolling was very effective for producing Nb-bearing high strength steel with high stretch- flangeability. It was suggested that the suppressed precipitation of grain boundary cementites and the decreased hardness difference between the ferrite matrix and bainite phases cause the excellent stretch-flangeability of ferrite-bainite duplex microstructure steel. Therefore, the formation and propagation of microcracks were suppressed relative to conventional HSLA steel with the ferrite and pearlite microstructure. In addition, the elongation improved compared with that of hot-rolled steel sheets using the conventional early cooling pattern because the volume fraction of polygonal ferrite increased.

Key words

ferrite-bainite duplex microstructure stretch-flangeability controlled cooling Nb added hot-rolled high strength steels automotive wheel discs 


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Copyright information

© Springer 1999

Authors and Affiliations

  • Yeol-Rae Cho
    • 1
  • Jin-Hwan Chung
    • 1
  • Hwang-Hoe Ku
    • 1
    • 2
  • In-Bae Kim
    • 1
    • 3
  1. 1.Technical Research LaboratoriesPohang Iron & Steel Co., Ltd.Kwangyang545-090Korea
  2. 2.Kwangyang Steel WorksPohang Iron & Steel Co., Ltd.KwangyangKorea
  3. 3.Department of Metallurgical EngineeringPusan National UniversityPusanKorea

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