ベイニティック・フェライト組織高強度熱延鋼板の伸びフランジ性

概要

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Recently, high strength hot rolled steel sheets have been applied to mainly chassises and wheels and high formability, especially high stretchflangeability is required on those parts. Bainitic-ferrite single phase microstructure has been proposed to obtain the high stretch-flange formability. In this paper, the effects of metallurgical factors of bainitic-ferrite single phase microstructure on stretch-flangeability is studied. The effects of atomic ratio of Ti by C of the bainitic ferrite steel and the void creation morphology of bainitic-ferrite, bainite and ferritepearlite steel after stretch flange formation are investigated. The bainitic-ferrite steels with access of 1.0 atomic ratio of Ti by C shows highest stretch-flangeability among the studied steels because cementite is not existed. Cemmentite existed in baintic-ferrite steels with 0.5 atomic ratio of Ti by C, bainite and ferrite-pearlite steels, causes the void initiation during stretch flange formation. In addition of above mentioned, the stretch-flangeability is deteriorated by TiC precipitate and increase grain size.
社団法人日本鉄鋼協会の論文