Invention Grant
- Patent Title: High-strength galvanized steel sheet with high yield ratio having excellent ductility and stretch flange formability and method for manufacturing the same
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Application No.: US13809953Application Date: 2011-07-12
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Publication No.: US09765413B2Publication Date: 2017-09-19
- Inventor: Yoshiyasu Kawasaki , Tatsuya Nakagaito , Shinjiro Kaneko , Yasunobu Nagataki , Keisuke Fukushi
- Applicant: Yoshiyasu Kawasaki , Tatsuya Nakagaito , Shinjiro Kaneko , Yasunobu Nagataki , Keisuke Fukushi
- Applicant Address: JP
- Assignee: JFE Steel Corporation
- Current Assignee: JFE Steel Corporation
- Current Assignee Address: JP
- Agency: DLA Piper LLP (US)
- Priority: JP2010-160401 20100715; JP2011-144093 20110629
- International Application: PCT/JP2011/066290 WO 20110712
- International Announcement: WO2012/008597 WO 20120119
- Main IPC: C21D6/00
- IPC: C21D6/00 ; B05D3/12 ; B05D3/02 ; C21D9/46 ; C22C38/00 ; C22C38/06 ; C23C2/40 ; C22C1/02

Abstract:
A high-strength galvanized steel sheet with high yield ratio having excellent ductility and stretch flange formability, the steel sheet having a chemical composition containing, by mass %, C: 0.04% or more and 0.13% or less, Si: 0.9% or more and 2.3% or less, Mn: 0.8% or more and 2.4% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.1% or less, N: 0.008% or less, and the balance being Fe and inevitable impurities and a microstructure including, in terms of area ratio, 94% or more of a ferrite phase and 2% or less of a martensite ferrite phase, wherein mean grain size of ferrite is 10 μm or less, Vickers hardness of ferrite is 140 or more, mean grain size of carbide particles existing at grain boundaries of ferrite is 0.5 μm or less, and aspect ratio of carbide particles existing at the grain boundaries of ferrite is 2.0 or less.
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