Title:
WELDED STEEL PIPE FOR LINEPIPE WITH SUPERIOR COMPRESSIVE STRENGTH AND SUPERIOR TOUGHNESS, AND PROCESS FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/2011/065578
Kind Code:
A1
Abstract:
A thick-walled steel pipe for linepipes is provided in which the decrease in yield stress caused by the Bauschinger effect is inhibited by optimizing the metallographic structure of a steel plate and in which the base metal and the weld heat-affected zone have excellent toughness. The welded steel pipe for linepipes, which has superior compressive strength and superior toughness, contains, in terms of mass%, 0.03-0.08% C, up to 0.10% Si, 1.00-2.00% Mn, up to 0.010% P, up to 0.0030% S, up to 0.06% Al, 0.005-0.020% Nb, 0.005-0.025% Ti, and 0.0010-0.0060% N, Ti (%)/N (%) being 2-4, the value of Ceq being 0.30 or more, and the remainder comprising Fe and incidental impurities. The steel pipe is characterized in that the metallographic structure of the base metal has specific values of the contents of bainite, island martensite (MA), and cementite, etc. and that the weld heat-affected zone has a specific metallographic structure. Also provided is a process for producing the welded steel pipe.
Inventors:
ISHIKAWA NOBUYUKI (JP)
TANIZAWA AKIHIKO (JP)
SUEYOSHI HITOSHI (JP)
HORIE MASAYUKI (JP)
KIYOTO YASUMITSU (JP)
TANIZAWA AKIHIKO (JP)
SUEYOSHI HITOSHI (JP)
HORIE MASAYUKI (JP)
KIYOTO YASUMITSU (JP)
Application Number:
PCT/JP2010/071527
Publication Date:
June 03, 2011
Filing Date:
November 25, 2010
Export Citation:
Assignee:
JFE STEEL CORP (JP)
ISHIKAWA NOBUYUKI (JP)
TANIZAWA AKIHIKO (JP)
SUEYOSHI HITOSHI (JP)
HORIE MASAYUKI (JP)
KIYOTO YASUMITSU (JP)
ISHIKAWA NOBUYUKI (JP)
TANIZAWA AKIHIKO (JP)
SUEYOSHI HITOSHI (JP)
HORIE MASAYUKI (JP)
KIYOTO YASUMITSU (JP)
International Classes:
C22C38/00; B21B3/00; B21C37/08; B21C37/30; B23K9/025; B23K9/23; C21D8/02; C22C38/14; C22C38/58
Foreign References:
| JP2009221534A | 2009-10-01 | |||
| JP2008121036A | 2008-05-29 | |||
| JP2006183133A | 2006-07-13 | |||
| JP2007119884A | 2007-05-17 | |||
| JP2003340518A | 2003-12-02 | |||
| JPH0949025A | 1997-02-18 | |||
| JP2003342639A | 2003-12-03 | |||
| JP2004035925A | 2004-02-05 | |||
| JP2002102931A | 2002-04-09 | |||
| JP2003340519A | 2003-12-02 | |||
| JP2008056962A | 2008-03-13 | |||
| JP2009052137A | 2009-03-12 |
Other References:
See also references of EP 2505681A4
Attorney, Agent or Firm:
OCHIAI, Kenichiro (JP)
Ken-ichiro Ochiai (JP)
Ken-ichiro Ochiai (JP)
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