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Title:
HIGH-STRENGTH STEEL PLATE AND PROCESS FOR PRODUCTION THEREOF, AND HIGH-STRENGTH STEEL PIPE
Document Type and Number:
WIPO Patent Application WO/2006/104261
Kind Code:
A1
Abstract:
The invention provides a high-strength steel plate which exhibits excellent cutting-crack resistance, Charpy absorption energy and DWTT characteristics, a low yield ratio and a tensile strength of 900 MPa or above; a process for the production thereof; and high-strength steel pipes made by using the same. The high-strength steel plate is one which contains by mass C: 0.03 to 0.12%, Si: 0.01 to 0.5%, Mn: 1.5 to 3%, Al: 0.01 to 0.08%, Nb: 0.01 to 0.08%, Ti: 0.005 to 0.025%, N: 0.001 to 0.01%, and at least one of Cu: 0.01 to 2%, Ni: 0.01 to 3%, Cr: 0.01 to 1%, Mo: 0.01 to 1%, and V: 0.01 to 0.1% and satisfies the following relationship (1) as to the contents of Ca, O and S, whose microstructure is composed of ferrite and a hard second phase at an area fraction of ferrite of 10 to 50% with the cementite contained in the hard second phase having a mean particle diameter of 0.5μm or below, and in which the content of Nb contained as carbide in the steel is at most 10% based on the whole Nb content of the steel. 1 < (1 - 130 × [O]) × [Ca]/(1.25 × [S]) < 3 ... (1)

Inventors:
SHIMAMURA JUNJI (JP)
ENDO SHIGERU (JP)
OKATSU MITSUHIRO (JP)
Application Number:
PCT/JP2006/307285
Publication Date:
October 05, 2006
Filing Date:
March 30, 2006
Export Citation:
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Assignee:
JFE STEEL CORP (JP)
SHIMAMURA JUNJI (JP)
ENDO SHIGERU (JP)
OKATSU MITSUHIRO (JP)
International Classes:
C21D8/02; C22C38/00
Domestic Patent References:
WO2003099482A12003-12-04
Foreign References:
JPH08209287A1996-08-13
JPH11302726A1999-11-02
JPH1017982A1998-01-20
JP2003041341A2003-02-13
JP2003293089A2003-10-15
JPH08311548A1996-11-26
JPH09184015A1997-07-15
Other References:
See also references of EP 1870484A4
Attorney, Agent or Firm:
Ochiai, Kenichiro c/o Patent, Application Dept (JFE Techno-Research Corporation 7th Floor, Yanagiya Building, 1-10, Nihonbashi 2-chom, Chuo-ku Tokyo, JP)
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