Title:
HIGH-STRENGTH STEEL SHEET, SHOCK-ABSORBING MEMBER, AND METHOD FOR PRODUCING HIGH-STRENGTH STEEL SHEET
Document Type and Number:
WIPO Patent Application WO/2021/070640
Kind Code:
A1
Abstract:
The purpose of the present invention is to provide: a high-strength steel sheet, which has a yield point elongation (YP-EL) of at least 1.0% and a tensile strength (TS) of at least 980 MPa and has excellent uniform ductility, bendability, and collapse characteristics; a shock-absorbing member; and a method for producing the high-strength steel sheet. The invention provides a high-strength steel sheet having a yield point elongation (YP-EL) of at least 1.0% and a tensile strength (TS) of at least 980 MPa, wherein: the high-strength steel sheet has a prescribed component composition; the steel structure is, in terms of area ratio, 30.0% to less than 80.0% ferrite and 3.0% to 30.0% martensite, and in volume ratio, at least 12.0% retained austenite; the average crystal grain size of the ferrite is 5.0 μm or less and the average crystal grain size of the retained austenite is 2.0 μm or less; the Mn content (mass%) in the retained austenite divided by the Mn content (mass%) in the steel is at least 1.50; at least 15% of the total retained austenite is retained austenite with an aspect ratio of at least 3.0 and at least 15% of the total retained austenite is retained austenite with an aspect ratio of less than 2.0; and the volume ratio Vγa of the retained austenite of the fractured part of a tensile test piece after an elevated temperature tensile test at 150℃ divided by the volume ratio Vγb of the retained austenite before the elevated temperature tensile test at 150℃ is at least 0.40.
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Inventors:
KAWASAKI YOSHIYASU (JP)
IWASAWA MUNEKA (JP)
TOJI YUKI (JP)
FUNAKAWA YOSHIMASA (JP)
IWASAWA MUNEKA (JP)
TOJI YUKI (JP)
FUNAKAWA YOSHIMASA (JP)
Application Number:
PCT/JP2020/036363
Publication Date:
April 15, 2021
Filing Date:
September 25, 2020
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C21D9/46; C22C38/00; C22C38/06; C22C38/60; C23C2/02; C23C2/06; C23C2/12; C23C2/28; C23C2/40; C25D5/26; C25D5/36; C25D5/50
Domestic Patent References:
| WO2018092817A1 | 2018-05-24 | |||
| WO2019188640A1 | 2019-10-03 | |||
| WO2017183349A1 | 2017-10-26 | |||
| WO2019194250A1 | 2019-10-10 |
Foreign References:
| JP2019014933A | 2019-01-31 | |||
| JPS61157625A | 1986-07-17 | |||
| JPH01259120A | 1989-10-16 | |||
| JP2003138345A | 2003-05-14 | |||
| JP2015078394A | 2015-04-23 |
Other References:
See also references of EP 4043594A4
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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