TY - JOUR
T1 - Effect of YAG laser cutting on stretch-flangeability of ultra high strength TRIP sheet steel with bainitic ferrite matrix
AU - Nagasaka, Akihiko
AU - Kubota, Yuichi
AU - Sugimoto, Koh Ichi
AU - Mio, Atsushi
AU - Hojo, Tomohiko
AU - Makii, Koichi
AU - Kawajiri, Masahiro
AU - Kitayama, Mitsunari
PY - 2010
Y1 - 2010
N2 - 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.
AB - 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.
KW - Bainitic ferrite matrix
KW - Retained austenite
KW - Stretch-flangeability
KW - TBF steel sheet
KW - TRIP-aided steel sheet
KW - Transformation- induced plasticity
KW - YAG laser cutting
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U2 - 10.2355/isijinternational.50.1441
DO - 10.2355/isijinternational.50.1441
M3 - Article
AN - SCOPUS:79956041067
VL - 50
SP - 1441
EP - 1446
JO - Transactions of the Iron and Steel Institute of Japan
JF - Transactions of the Iron and Steel Institute of Japan
SN - 0915-1559
IS - 10
ER -