Invention Grant
- Patent Title: High-strength steel sheet having excellent ductility and low-temperature toughness, and method for producing same
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Application No.: US15023520Application Date: 2014-09-25
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Publication No.: US10066274B2Publication Date: 2018-09-04
- Inventor: Koji Kasuya , Tadao Murata , Sae Mizuta , Yuichi Futamura
- Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.)
- Applicant Address: JP Kobe-shi
- Assignee: Kobe Steel, Ltd.
- Current Assignee: Kobe Steel, Ltd.
- Current Assignee Address: JP Kobe-shi
- Agency: Oblon, McClelland, Maier & Neustadt, L.L.P.
- Priority: JP2013-202536 20130927; JP2014-071907 20140331
- International Application: PCT/JP2014/075445 WO 20140925
- International Announcement: WO2015/046339 WO 20150402
- Main IPC: C22C38/02
- IPC: C22C38/02 ; C22C38/04 ; C22C38/06 ; C21D8/02 ; C21D9/46 ; C22C38/00 ; C22C38/08 ; C22C38/12 ; C22C38/14 ; C22C38/16 ; C22C38/38 ; C22C38/18 ; C23C2/02 ; C23C2/28 ; C23C2/06
Abstract:
A high-strength steel sheet of the present invention is a steel sheet satisfying a predetermined component composition. A metal structure of the steel sheet is composed of polygonal ferrite, high-temperature region generated bainite, low-temperature region generated bainite and retained austenite each having a predetermined area percent, and a distribution using each average IQ of predetermined crystal grains determined by electron backscatter diffraction satisfies Equations (1) and (2) below. According to the present invention, a high-strength steel sheet having excellent ductility and low-temperature toughness can be realized even at a tensile strength of 780 MPa or more. (IQave−IQmin)/(IQmax−IQmin)≥0.40 (1) (σIQ)/(IQmax−IQmin)≤0.25 (2)
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