Title:
THICK STEEL SHEET HAVING HIGH STRENGTH AND METHOD FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/2010/055609
Kind Code:
A1
Abstract:
A thick steel sheet having high strength, which contains (by mass%) 0.18-0.23% of C, 0.1-0.5% of Si, 1.0-2.0% of Mn, 0.020% or less of P, 0.010% or less of S, more than 0.5% and not more than 3.0% of Cu, 0.25-2.0% of Ni, 0.003-0.10% of Nb, 0.05-0.15% of Al, 0.0003-0.0030% of B and 0.006% or less of N, with the remainder being Fe and unavoidable impurities and has such a chemical composition that Pcm becomes 0.39% or less, wherein the Ac3 phase transformation point is 850˚C or lower, the volume fraction of a martensite structure is 90% or more, the yield strength is 1300 MPa or more, the tensile strength [TS] is 1400 to 1650 MPa, and the [TS] and the prior austenite crystal grain size number [Nγ] have the relationship represented by the following formulae: Nγ ≥ ([TS]-1400)×0.006+7.0 when [TS] is less than 1550 MPa and Nγ ≥ ([TS]-1550)×0.01+7.9 when [TS] is 1550 MPa or more.
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Inventors:
KUMAGAI TATSUYA (JP)
USAMI AKIRA (JP)
OKA MASAHARU (JP)
USAMI AKIRA (JP)
OKA MASAHARU (JP)
Application Number:
PCT/JP2009/005315
Publication Date:
May 20, 2010
Filing Date:
October 13, 2009
Export Citation:
Assignee:
NIPPON STEEL CORP (JP)
KUMAGAI TATSUYA (JP)
USAMI AKIRA (JP)
OKA MASAHARU (JP)
KUMAGAI TATSUYA (JP)
USAMI AKIRA (JP)
OKA MASAHARU (JP)
International Classes:
C22C38/00; B21B1/38; B21B3/00; C21D8/02; C22C38/16; C22C38/58
Foreign References:
| JP2007302974A | 2007-11-22 | |||
| JP2005097725A | 2005-04-14 | |||
| JP2007308743A | 2007-11-29 | |||
| JPH06248386A | 1994-09-06 | |||
| JP2008288859A | 2008-11-27 | |||
| JPH0790488A | 1995-04-04 | |||
| JPS6480903A | 1989-03-27 | |||
| JPS6480903A | 1989-03-27 | |||
| JPH11229075A | 1999-08-24 | |||
| JPH01149921A | 1989-06-13 | |||
| JPH01229075A | 1989-09-12 | |||
| JPH09263876A | 1997-10-07 | |||
| JP2001107139A | 2001-04-17 | |||
| JPH08311601A | 1996-11-26 |
Other References:
TETSU-TO-HAGANÉ, vol. 83, 1997, pages 454
See also references of EP 2290116A4
See also references of EP 2290116A4
Attorney, Agent or Firm:
SHIGA, Masatake et al. (JP)
Masatake Shiga (JP)
Masatake Shiga (JP)
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