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Title:
THICK HIGH-TENSILE-STRENGTH HOT-ROLLED STEEL SHEET WITH EXCELLENT LOW-TEMPERATURE TOUGHNESS AND PROCESS FOR PRODUCTION OF SAME
Document Type and Number:
WIPO Patent Application WO/2010/087511
Kind Code:
A1
Abstract:
Provided is a process for the production of a thick high-tensile -strength hot-rolled steel sheet which combines a high strength of 510MPa or higher and high ductility and is well balanced between strength and ductility, and which exhibits excellent low -temperature toughness. Also provided is a high-tensile -strength hot-rolled steel sheet having a composition which contains 0.02 to 0.08% of C, 0.01 to 0.10% of Nb, and 0.001 to 0.05% of Ti, the contents of C, Ti and Nb satisfying the relationship: (Ti + (Nb/2))/C < 4, with the balance being Fe and unavoidable impurities. In the high-tensile-strength hot-rolled steel sheet, the matrix phase of the structure at a depth of 1mm from the surface in the sheet thickness direction is ferrite, tempered martensite, or a mixed phase of both; the matrix phase of the structure at the center in the sheet thickness direction is ferrite; and the difference (ΔV) between the second phase fraction (vol%) of the structure at a depth of 1mm from the surface in the sheet thickness direction and the second phase fraction (vol%) of the structure at the center in the sheet thickness direction is 2% or less.

Inventors:
KAMI CHIKARA (JP)
NAKATA HIROSHI (JP)
NAKAGAWA KINYA (JP)
Application Number:
PCT/JP2010/051646
Publication Date:
August 05, 2010
Filing Date:
January 29, 2010
Export Citation:
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Assignee:
JFE STEEL CORP (JP)
KAMI CHIKARA (JP)
NAKATA HIROSHI (JP)
NAKAGAWA KINYA (JP)
International Classes:
C22C38/00; B21B1/26; B21B3/00; C21D8/02; C22C38/14; C22C38/58
Foreign References:
JP2008274323A2008-11-13
JP2007138290A2007-06-07
JP2004315957A2004-11-11
JP2005281838A2005-10-13
JP2010037567A2010-02-18
JPH08319538A1996-12-03
JPH09296216A1997-11-18
JP2008056962A2008-03-13
JP2001240936A2001-09-04
JP2001207220A2001-07-31
JP2004315957A2004-11-11
Other References:
See also references of EP 2392682A4
Attorney, Agent or Firm:
OCHIAI, Kenichiro (JP)
Ken-ichiro Ochiai (JP)
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