Title:
HIGH-STRENGTH STEEL SHEET
Document Type and Number:
WIPO Patent Application WO/2015/198582
Kind Code:
A1
Abstract:
Provided is a low-cost high-strength steel sheet that has excellent bendability, with a tensile strength of at least 780 MPa, and that is well-suited for the manufacture of structural members for machines such as automobiles. The high-strength steel sheet has a specific component composition. Oxide inclusions present in the high-strength steel sheet within 100 µm of the surface and having a particle major axis with a length of at least 2 µm satisfy specific conditions. The metallographic structure of the high-strength steel sheet, by volume ratio, is 20–65% of a martensite phase, 40–80% of a ferrite phase, less than 5% (including 0%) of a bainite phase, and less than 5% (including 0%) of an austenite phase. The total volume ratio of metallographic structures other than the martensite phase and the ferrite phase is 10% or less (including 0%). The tensile strength of the high-strength steel sheet is at least 780 MPa. Here, "particle major axis" refers to the major axis of particles evaluated in a cross-section containing the rolling direction of the high-strength steel sheet.
Inventors:
HASEGAWA KOHEI (JP)
ONO YOSHIHIKO (JP)
MURAI TAKESHI (JP)
SAKURAI MICHITAKA (JP)
ONO YOSHIHIKO (JP)
MURAI TAKESHI (JP)
SAKURAI MICHITAKA (JP)
Application Number:
PCT/JP2015/003114
Publication Date:
December 30, 2015
Filing Date:
June 22, 2015
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; C22C38/06; C22C38/58; C21D9/46
Foreign References:
| JP2002363694A | 2002-12-18 | |||
| JP2011042879A | 2011-03-03 | |||
| JP2006188755A | 2006-07-20 | |||
| JP2003119546A | 2003-04-23 |
Attorney, Agent or Firm:
KUMASAKA, Akira et al. (JP)
Akira Kumasaka (JP)
Akira Kumasaka (JP)
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