高強度熱延鋼板の伸びフランジ性におよぼすレーザー切断の影響

概要

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Effect of laser beam cutting on stretch flangeability of high strength hot rolled steel sheets having different chemical compositions was investigated and the results were discussed from metallurgical point of view. Hole notches with a diameter of 10mm were pierced by either laser beam cutting or mechanical punching method for hole expansion test. Laser beam cutting resulted in much higher stretch flangeability than mechanical punching because the former cut surface was smooth, defect-free and had thin heat-affected layer in contrast with a rugged punched surface containing a number of microvoids and thick work-hardened layer. Change in hole expanding ratio of laser cut steel sheet was well explained by the hardness of the heat affected layer. A carbon equivalent equation which agrees well with the variation in hardness was tentatively proposed by modifing the WES C_<eq.>. It indicates that the steel sheet strengthened by the chemistry leading to less quench hardenability shows higher stretch flangeability. Increase in manganese sulfide inclusion markedly lowered stretch flangeability.
社団法人日本鉄鋼協会の論文
1985-12-01