Title:
HIGH-STRENGTH STEEL SHEET, IMPACT ABSORBING MEMBER, AND METHOD FOR MANUFACTURING HIGH-STRENGTH STEEL SHEET
Document Type and Number:
WIPO Patent Application WO/2021/070639
Kind Code:
A1
Abstract:
The purpose of the present invention is to provide: a high-strength steel sheet having a yield elongation (YP-EL) of 1% or more and a tensile strength (TS) of 980 MPa or more, and also having excellent uniform ductility, bendability and collapse characteristics; an impact absorbing member; and a method for manufacturing the high-strength steel sheet. Provided is a high-strength steel sheet having a yield elongation (YP-EL) of 1% or more and a tensile strength (TS) of 980 MPa or more, wherein the high-strength steel sheet has a prescribed component composition, and the steel structure thereof comprises at least 30.0% and less than 80.0% of ferrite, 3.0-30.0% of martensite, and 0-3.0% of bainite in terms of area ratio, and at least 12.0% of residual austenite in terms of volume ratio. In addition, among the total number of residual austenite grains, the ratio of residual austenite grains adjoining residual austenite grains having different crystal orientations is 0.60 or more. Furthermore, the average crystal grain size of the ferrite is 5.0 µm or less; the average crystal grain size of the residual austenite is 2.0 µm or less; a value obtained by dividing the content (mass%) of Mn in the residual austenite by the content (mass%) of Mn in the steel is 1.50 or greater; and a value obtained by dividing the volume ratio Vγa of residual austenite in a fracture portion of a tensile test piece after performing the hot tensile test at 150°C by the the volume ratio Vγb of residual austenite before performing the hot tensile test at 150°C is 0.40 or greater.
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Inventors:
KAWASAKI YOSHIYASU (JP)
TOJI YUKI (JP)
IWASAWA MUNEKA (JP)
FUTATSUKA TAKAYUKI (JP)
SATO KENTARO (JP)
TOJI YUKI (JP)
IWASAWA MUNEKA (JP)
FUTATSUKA TAKAYUKI (JP)
SATO KENTARO (JP)
Application Number:
PCT/JP2020/036362
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 | |||
| WO2019188643A1 | 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 4043593A4
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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