Title:
HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT WORKABILITY, MOLTEN GALVANIZED HIGH-STRENGTH STEEL SHEET, AND METHOD FOR PRODUCING THE SAME
Document Type and Number:
WIPO Patent Application WO/2010/061972
Kind Code:
A1
Abstract:
Provided is a high-strength cold-rolled steel sheet having a TS of 1,180 MPa or greater and excellent workability, such as stretch flange workability and bendability. Also provided are a molten galvanized high-strength steel sheet, and a method for producing the same. The high-strength cold-rolled steel sheet having excellent workability has a composition that comprises, by mass%, C: 0.05 to 0.3, Si: 0.5 to 2.5, Mn: 1.5 to 3.5, P: 0.001 to 0.05, S: 0.0001 to 0.01, Al: 0.001 to 0.1, N: 0.0005 to 0.01, and Cr: 1.5 or less (including 0) and satisfies formulas (1) and (2), with the balance being Fe and inevitable impurities. The steel sheet has a microtexture wherein there is a ferrite phase and a martensite phase, the percentage of the texture total surface area occupied by martensite phase is 30% or greater, (the surface area occupied by martensite phase)/(surface area occupied by ferrite phase) exceeds 0.45 but is less than 1.5, and the average particle diameter of the martensite phase is 2 µm or larger. [C]1/2×([Mn]+0.6×[Cr])≧1-0.12×[Si]・・・(1), 550-350×C*-40×[Mn]-20×[Cr]+30×[Al]≧340・・・(2) where C*=[C]/(1.3×[C]+0.4×[Mn]+0.45×[Cr]-0.75).
Inventors:
KANEKO SHINJIRO (JP)
KAWASAKI YOSHIYASU (JP)
NAKAGAITO TATSUYA (JP)
MATSUOKA SAIJI (JP)
KAWASAKI YOSHIYASU (JP)
NAKAGAITO TATSUYA (JP)
MATSUOKA SAIJI (JP)
Application Number:
PCT/JP2009/070367
Publication Date:
June 03, 2010
Filing Date:
November 27, 2009
Export Citation:
Assignee:
JFE STEEL CORP (JP)
KANEKO SHINJIRO (JP)
KAWASAKI YOSHIYASU (JP)
NAKAGAITO TATSUYA (JP)
MATSUOKA SAIJI (JP)
KANEKO SHINJIRO (JP)
KAWASAKI YOSHIYASU (JP)
NAKAGAITO TATSUYA (JP)
MATSUOKA SAIJI (JP)
International Classes:
C22C38/00; C21D9/46; C22C18/00; C22C38/38; C22C38/58; C23C2/02; C23C2/06; C23C2/28
Foreign References:
| JP2007262494A | 2007-10-11 | |||
| JP2001207235A | 2001-07-31 | |||
| JP2000017385A | 2000-01-18 | |||
| JP2003113442A | 2003-04-18 | |||
| JP2007277729A | 2007-10-25 | |||
| JP2007302918A | 2007-11-22 | |||
| JP2000192191A | 2000-07-11 | |||
| JPH05179345A | 1993-07-20 | |||
| JP2009179852A | 2009-08-13 | |||
| JPH0913147A | 1997-01-14 | |||
| JPH11279691A | 1999-10-12 | |||
| JP2002069574A | 2002-03-08 | |||
| JP2003055751A | 2003-02-26 |
Other References:
THE JAPAN INSTITUTE OF METALS, MATERIA JAPAN, vol. 46, no. 4, 2007, pages 251 - 258
See also references of EP 2371979A4
See also references of EP 2371979A4
Attorney, Agent or Firm:
OCHIAI, Kenichiro (JP)
Ken-ichiro Ochiai (JP)
Ken-ichiro Ochiai (JP)
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