Effect of tempering temperature on stretch-flangeability of maltensitic steels

Shigeo Ohtani, Tatsuya Morikawa, Kenji Higashida, Shun Ichi Hashimoto, Hiroyuki Haren

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    5 Citations (Scopus)

    Abstract

    The effect of microstructures on the stretch-flangeability has been investigated using high-strength martensitic steels tempered at various temperatures. For the index of the stretch-flangeability, hole-expanding ratio A was measured using plate specimens with a hole introduced by a punching process. Tensile tests were also carried out using the same tempered specimens. A increased with increasing tempering temperature, and took the maximum value at 773K, and then decreased in the specimens tempered at temperatures higher than 773K. On the other hand, in the tensile tests, total elongations or local elongations increase with increasing tempering temperature up to 973K, and decreased in the specimen tempered at 1073K where typical dual phase microstructure was observed. Microstructural observations around the holes formed by punching process suggest that the maximum value of λ is determined by the balance between the recovery enhancing ductility and the growth of cementite size causing void formation during the punching process. It is to be noted that grain refinement due to severe plastic deformation during punching process was observed around the holes, which might contribute to enhancing the stretch-flangeability.

    Original languageEnglish
    Pages (from-to)406-413
    Number of pages8
    JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
    Volume96
    Issue number6
    DOIs
    Publication statusPublished - 2010

    All Science Journal Classification (ASJC) codes

    • Condensed Matter Physics
    • Physical and Theoretical Chemistry
    • Metals and Alloys
    • Materials Chemistry

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