Title:
HIGH-STRENGTH STEEL SHEET AND METHOD FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/2018/092816
Kind Code:
A1
Abstract:
After adopting a predetermined constituent composition, this steel microstructure is set to have, in terms of surface area ratio, 15% to 55% ferrite and 15% to 30% martensite, and in terms of volume ratio, at least 12% retained austenite, the average crystal grain sizes of the ferrite, martensite and retained austenite are set to 4.0 μm or less, 2.0 μm or less and 2.0 μm or less respectively, the average aspect ratios of the ferrite, martensite, and retained austenite crystal grains are set to exceed 2.0 but not exceed 15.0 respectively, and the value obtained by dividing the Mn content (% mass) in the retained austenite by the Mn content (% mass) in the ferrite is set to at least 2.0. As a result, a high-strength steel sheet having excellent ductility and pore expandability, having a yield ratio (YR) of less than 68% and a tensile strength (TS) of at least 980 MPa is provided.
Inventors:
KAWASAKI YOSHIYASU (JP)
YAMASHITA TAKAKO (JP)
UENO MASAYASU (JP)
TOJI YUKI (JP)
KOBAYASHI TAKASHI (JP)
FUNAKAWA YOSHIMASA (JP)
YAMASHITA TAKAKO (JP)
UENO MASAYASU (JP)
TOJI YUKI (JP)
KOBAYASHI TAKASHI (JP)
FUNAKAWA YOSHIMASA (JP)
Application Number:
PCT/JP2017/041147
Publication Date:
May 24, 2018
Filing Date:
November 15, 2017
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C21D9/46; C22C38/00; C22C18/04; C22C38/14; C22C38/58; C22C38/60
Domestic Patent References:
| WO2016067626A1 | 2016-05-06 | |||
| WO2016067624A1 | 2016-05-06 |
Foreign References:
| JPS61157625A | 1986-07-17 | |||
| JP2003138345A | 2003-05-14 | |||
| JPH01259120A | 1989-10-16 |
Other References:
See also references of EP 3543365A4
Attorney, Agent or Firm:
SUGIMURA Kenji (JP)
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