超高張力TRIP型ベイニティックフェライト鋼板の伸びフランジ性に及ぼすYAGレーザ切断の影響(加工・加工熱処理)

概要

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Effect of YAG laser cutting on stretch-flangeability of 0.2C-1.5Si-1.5Mn (mass%) ultra high-strength TRIP-aided sheet steel with bainitic ferrite matrix (TBF steel) having different martensite start temperatures, which were austempered at 375 or 450℃, was investigated for automotive applications. Hole notches of 5mm diameter were produced by YAG laser cutting or mechanical punching for hole-expanding test. The stretch-flangeability was evaluated using hole-expanding ratio (λ). In TBF steel, laser cutting resulted in much higher stretch-flangeability than mechanical punching. The hole-expanding ratio (λ) of TBF steel austempered at 375℃ in the case of laser cutting at average powers between 50 and 100W was higher than that at 450℃, and also higher than mechanical punching. Furthermore, the strength-stretch-flangeability balance (TS×λ) of TBF steel austempered at 375℃ showed the highest stretch-flangeability by laser cutting at 100W. We found that compared with mechanical punching, YAG laser cutting contributed to the improvement of the TS×λ of 1100MPa class TBF steel with fine bainitic ferrite matrix.
社団法人日本鉄鋼協会の論文
2008-09-01