Invention Grant
- Patent Title: High-strength steel sheet and method for manufacturing same
- Patent Title (中): 高强度钢板及其制造方法
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Application No.: US14349234Application Date: 2012-10-02
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Publication No.: US08876987B2Publication Date: 2014-11-04
- Inventor: Hiroshi Matsuda , Yoshimasa Funakawa , Kaneharu Okuda , Kazuhiro Seto
- Applicant: JFE Steel Corporation
- Applicant Address: JP
- Assignee: JFE Steel Corporation
- Current Assignee: JFE Steel Corporation
- Current Assignee Address: JP
- Agency: DLA Piper LLP (US)
- Priority: JP2011-220495 20111004
- International Application: PCT/JP2012/006306 WO 20121002
- International Announcement: WO2013/051238 WO 20130411
- Main IPC: C22C38/04
- IPC: C22C38/04 ; C22C38/06 ; C22C38/02 ; C21D8/02 ; C22C38/00 ; C22C38/12 ; C22C38/14 ; C23C2/02 ; C22C38/28 ; C22C38/38 ; C22C38/32 ; C22C38/16 ; C22C38/08

Abstract:
A high strength pressed member has excellent ductility and stretch flangeability and tensile strength of 780-1400 MPa, with a predetermined steel composition and steel microstructure relative to the entire microstructure of steel sheet, where area ratio of martensite 5-70%, area ratio of retained austenite 5-40%, area ratio of bainitic ferrite in upper bainite 5% or more, and total thereof is 40% or more, 25% or more of martensite is tempered martensite, polygonal ferrite area ratio is above 10% and below 50% to the entire microstructure of steel sheet, and average grain size is 8 μm or less, average diameter of a group of polygonal ferrite grains is 15 μm or less, the group of polygonal ferrite grains represented by a group of ferrite grains of adjacent polygonal ferrite grains, and average carbon content in retained austenite is 0.70 mass % or more and tensile strength is 780 MPa or more.
Public/Granted literature
- US20140242416A1 HIGH-STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING SAME Public/Granted day:2014-08-28
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