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Metallurgical and Materials Transactions A

, Volume 50, Issue 2, pp 884–893 | Cite as

Reduction of Cracks During Punching Process by Cementite in High Tensile Strength Steel Sheets

  • Takehiro Okano
  • Chikara InoueEmail author
  • Shinsuke Suzuki
  • Kazuhiko Yamazaki
  • Shunsuke Toyoda
Article
  • 55 Downloads

Abstract

An experimental study on high tensile strength steel sheets with ferritic and ferrite–cementite microstructures was performed with the objective of determining the crack formation and propagation mechanism in the punching process. In addition, the effect of dispersed cementites was also investigated. SEM, EPMA, and EBSD analyses confirmed that voids initiate at the ferrite-inclusion/precipitate (TiN, TiS, and cementite) interface, and the voids then propagate into the ferrite matrix by cleavage. EPMA, EBSD, and TEM/EDS demonstrated that cracks which formed within and near a center segregation area propagate along the Mn center segregation by intergranular fracture due to Mn segregation at the grain boundary. In addition to TiN and TiS, observation of the number of cracks, the length of cracks in the punched surface, and the number density of voids in tensile fracture parts indicated that dispersed cementites are also void formation factors, and cementites decrease the number of cracks and average crack length in the punched surface of ferrite–cementite steel sheets by reducing the stress applied to the voids.

Notes

Acknowledgments

The authors are deeply grateful to Mr. S. Takagi, Mr. T. Mino, and Mr. S. Enomoto (Kagami Memorial Research Institute for Materials Science and Technology, Waseda Univ.) for technical support of the EPMA, EBSD, and TEM/EDS analyses.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2018

Authors and Affiliations

  • Takehiro Okano
    • 1
  • Chikara Inoue
    • 1
    Email author
  • Shinsuke Suzuki
    • 2
  • Kazuhiko Yamazaki
    • 3
  • Shunsuke Toyoda
    • 3
  1. 1.Graduate School of Fundamental Science and EngineeringWaseda UniversityShinjukuJapan
  2. 2.Faculty of Fundamental Science and Engineering, Kagami Memorial Research Institute of Materials Science and TechnologyWaseda UniversityShinjukuJapan
  3. 3.JFE Steel CorporationKawasakiJapan

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