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.:
Date of Patent:
Dec. 27, 2011
Filed:
Dec. 04, 2007
Takuya Hara, Tokyo, JP;
Hitoshi Asahi, Tokyo, JP;
Takuya Hara, Tokyo, JP;
Hitoshi Asahi, Tokyo, JP;
Nippon Steel Corporation, Tokyo, JP;
Abstract
The present invention provides high strength thick welded steel pipe for line pipe superior in low temperature toughness, and a method of production of the same. A base material steel plate containing C: 0.010 to 0.050%, Si: 0.01 to 0.50%, Mn: 0.50 to 2.00%, Al: 0.020% or less, Ti: 0.003 to 0.030%, and Mo: 0.10 to 1.50%, having a carbon equivalent Ceq of 0.30 to 0.53, having a crack susceptability parameter Pcm of 0.10 to 0.20, satisfying formula 3, comprised an area ratio of 20% or less of polygonal ferrite and an area ratio of 80% or more of bainite, and having an effective crystal grain size of 20 μm or less is formed into a pipe shape, then seam welded to make the effective crystal grain size of the heat affected zone 150 μm or less:10C+100Al+5Mo+5Ni<3.3  formula 3.