Effect of YAG laser cutting on stretch-flangeability of ultra high strength TRIP sheet steel with bainitic ferrite matrix

Akihiko Nagasaka, Yuichi Kubota, Koh Ichi Sugimoto, Atsushi Mio, Tomohiko Hojo, Koichi Makii, Masahiro Kawajiri, Mitsunari Kitayama

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

The effect of YAG laser cutting on stretch-flangeability of ultra high strength TRIP-aided steel sheets with bainitic ferrite matrix (TBF steel sheet) austempered at 375 or 450°C, was investigated for automotive applications. Holes of 5 mm diameter for hole-expanding test were produced by YAG laser cutting and mechanical punching and the stretch-flangeability was evaluated by measurement of the hole-expanding ratio (l ). In TBF steel sheet, laser cut specimens show higher stretch-flangeability than mechanically punched specimens. The hole-expanding ratio (λ) of TBF steel sheet austempered at 375°C in the case of laser cutting at powers between 50 and 100W was higher than those austempered at 450°C. Furthermore, the strength-stretch-flangeability balance (TS×λ ) of TBF steel sheet austempered at 375°C showed the highest value after laser cutting at 100W. Compared to mechanical punching, YAG laser cutting contributed to the improvement of the TS×λ to 1 100MPa with TBF steel sheet possessing fine bainitic ferrite matrix.

Original languageEnglish
Pages (from-to)1441-1446
Number of pages6
JournalIsij International
Volume50
Issue number10
DOIs
Publication statusPublished - 2010

Keywords

  • Bainitic ferrite matrix
  • Retained austenite
  • Stretch-flangeability
  • TBF steel sheet
  • TRIP-aided steel sheet
  • Transformation- induced plasticity
  • YAG laser cutting

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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