Title:
STEEL SHEET, MEMBER, METHOD FOR PRODUCING SAID STEEL SHEET, AND METHOD FOR PRODUCING SAID MEMBER
Document Type and Number:
WIPO Patent Application WO/2022/185805
Kind Code:
A1
Abstract:
Provided are an ultrahigh-strength steel sheet having excellent moldability, delayed-fracture resistance, and LME resistance, and a method for producing the same. The steel sheet has a component composition containing, in terms of mass%, 0.24-0.40% of C, 0.2-1.0% of Si, 1.5-3.5% of Mn, 0.002-0.010% of P, 0.0002-0.0020% of S, at most 0.50% (not including 0%) of sol. Al, and 0.0006-0.01% of N, with the remainder made up of Fe and unavoidable impurities. The steel sheet has a steel structure containing, in terms of area ratio, 40-78% of martensite, 20-58% of bainite, and at least 2% of retained austenite. The average particle size of carbides in the tempered martensite of the martensite is at most 0.40 μm, the average C content in the retained austenite is at least 0.5 mass%, the Si concentration from the surface of the steel sheet up to 100 μm in the plate thickness direction is at most 1.3 mass %, and the tensile strength of the steel sheet is at least 1470 MPa.
Inventors:
HATA KATSUYA (JP)
YOSHIOKA SHIMPEI (JP)
KANEKO SHINJIRO (JP)
YOSHIOKA SHIMPEI (JP)
KANEKO SHINJIRO (JP)
Application Number:
PCT/JP2022/003321
Publication Date:
September 09, 2022
Filing Date:
January 28, 2022
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; C21D9/46; C22C38/06; C22C38/60
Domestic Patent References:
| WO2020090303A1 | 2020-05-07 | |||
| WO2020230796A1 | 2020-11-19 | |||
| WO2016152163A1 | 2016-09-29 | |||
| WO2021200580A1 | 2021-10-07 |
Foreign References:
| JP6291289B2 | 2018-03-14 | |||
| JP6288394B2 | 2018-03-07 | |||
| JP6635236A |
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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