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The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.

The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.

Patent No.:

US 8871039 B1

PDFFull Text
Date of Patent:
Oct. 28, 2014

Filed:

Sep. 13, 2011

Thick welded steel pipe excellent in low temperature toughness, manufacturing method of thick welded steel pipe excellent in low temperature toughness, and steel plate for manufacturing thick welded steel pipe

Applicants:

Yasuhiro Shinohara, Tokyo, JP;

Takuya Hara, Tokyo, JP;

Naoki Doi, Tokyo, JP;

Eiichi Yamashita, Tokyo, JP;

Inventors:

Yasuhiro Shinohara, Tokyo, JP;

Takuya Hara, Tokyo, JP;

Naoki Doi, Tokyo, JP;

Eiichi Yamashita, Tokyo, JP;

Assignee:

Nippon Steel & Sumitomo Metal Corporation, Tokyo, JP;

Attorney:

Birch, Stewart, Kolasch & Birch, LLP

Primary Examiner:

Deborah Yee

Int. Cl.
CPC ...
C22C 38/48 (2006.01); C22C 38/50 (2006.01); C21D 8/10 (2006.01); C22C 38/26 (2006.01); C22C 38/24 (2006.01); C21D 9/08 (2006.01); B23K 35/24 (2006.01); C22C 38/16 (2006.01); C22C 38/02 (2006.01); C22C 38/00 (2006.01); C22C 38/06 (2006.01); B23K 35/30 (2006.01); B23K 9/025 (2006.01); C22C 38/12 (2006.01); C22C 38/08 (2006.01); C22C 38/14 (2006.01); B23K 9/18 (2006.01); C22C 38/04 (2006.01); C21D 8/02 (2006.01);
U.S. Cl.
CPC ...
C21D 9/08 (2013.01); C21D 2211/005 (2013.01); C22C 38/16 (2013.01); C22C 38/02 (2013.01); C22C 38/005 (2013.01); B23K 2203/04 (2013.01); C22C 38/06 (2013.01); C22C 38/002 (2013.01); B23K 35/3053 (2013.01); B23K 9/0253 (2013.01); C22C 38/12 (2013.01); C22C 38/08 (2013.01); C22C 38/14 (2013.01); B23K 35/3073 (2013.01); B23K 9/186 (2013.01); C22C 38/04 (2013.01); C21D 8/02 (2013.01); C22C 38/00 (2013.01); C21D 2211/001 (2013.01); B23K 2201/06 (2013.01); C21D 8/105 (2013.01); Y10S 148/909 (2013.01);
Abstract

The present invention provides a thick welded steel pipe excellent in low temperature toughness in which contents of Mn and Mo satisfy (Expression 1) below, Pcm obtained by (Expression 2) below is 0.16 to 0.19, and a metal structure of a base material steel plate consists of ferrite being 30 to 95% in an area ratio and a low temperature transformation structure, and in a metal structure of a coarse-grained HAZ, an area ratio of grain boundary ferrite is 1.5% or more, the total area ratio of the grain boundary ferrite and intragranular ferrite is not less than 11% nor more than 90%, an area ratio of MA is 10% or less, and its balance is composed of bainite.1.2325≦(0.85×[Mn]−[Mo])≦1.5215  (Expression 1)andPcm=[C]+[Si]/30+([Mn]+[Cu]+[Cr])/20+[Ni]/60+[Mo]/15+[V]/10  (Expression 2).

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