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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 9200342 B1

PDFFull Text
Date of Patent:
Dec. 01, 2015

Filed:

Jun. 30, 2011

Hot-rolled steel sheet and manufacturing method thereof

Applicants:

Tatsuo Yokoi, Tokyo, JP;

Hiroshi Abe, Tokyo, JP;

Osamu Yoshida, Tokyo, JP;

Yasuhiro Miyatani, Tokyo, JP;

Shinichi Araki, Tokyo, JP;

Osamu Kawano, Tokyo, JP;

Inventors:

Tatsuo Yokoi, Tokyo, JP;

Hiroshi Abe, Tokyo, JP;

Osamu Yoshida, Tokyo, JP;

Yasuhiro Miyatani, Tokyo, JP;

Shinichi Araki, Tokyo, JP;

Osamu Kawano, Tokyo, JP;

Assignee:

NIPPON STEEL & SUMITOMO METAL CORPORATION, Tokyo, JP;

Attorney:

Kenyon & Kenyon LLP

Primary Examiner:

Weiping Zhu

Int. Cl.
CPC ...
C21D 8/00 (2006.01); C21D 8/02 (2006.01); C21D 9/08 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01); C22C 38/58 (2006.01); C21D 8/10 (2006.01); C21D 9/46 (2006.01); C22C 38/06 (2006.01);
U.S. Cl.
CPC ...
C21D 8/005 (2013.01); C21D 8/02 (2013.01); C21D 8/0226 (2013.01); C21D 8/0263 (2013.01); C21D 8/10 (2013.01); C21D 9/08 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/12 (2013.01); C22C 38/14 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (2013.01); C22C 38/58 (2013.01);
Abstract

A hot-rolled steel sheet according to the present invention is a steel sheet containing a predetermined components, and satisfying O<S/Ca<0.8, N−14/48×Ti≧'0' (zero) %. It is a high-strength hot-rolled steel sheet for a spiral pipe excellent in low-temperature toughness in which a pro-eutectoid ferrite fraction is 3% or more and 20% or less, and the other is a low-temperature transformation phase in a microstructure at a depth of a half thickness of a sheet thickness from a steel sheet surface, a number average crystal grain size of a whole of the microstructure is 2.5 μm or less, an area average grain size is 9 μm or less, a standard deviation of the area average grain size is 2.3 μm or less, and a reflected X-ray intensity ratio {211}/{111} in a direction and in a {111} direction relative to a plane in parallel to the steel sheet surface at the depth of the half thickness of the sheet thickness from the steel sheet surface is 1.1 or more. The steel sheet has both high-toughness and strength of API5L-X80 standard or more.

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