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:
Aug. 19, 2008
Filed:
Dec. 01, 2005
Shushi Ikeda, Kobe, JP;
Koichi Sugimoto, Nagano, JP;
Yoichi Mukai, Kakogawa, JP;
Hiroshi Akamizu, Kakogawa, JP;
Shushi Ikeda, Kobe, JP;
Koichi Sugimoto, Nagano, JP;
Yoichi Mukai, Kakogawa, JP;
Hiroshi Akamizu, Kakogawa, JP;
Kabushiki Kaisha Kobe Seiko Sho, Kobe-shi, JP;
Shinshu TLO Co., Ltd., Ueda-shi, JP;
Abstract
The present invention provide a TRIP-type composite structure steel plate of the TPF steel type in which elongation and stretch flange formability at room temperature are improved by controlling the morphology of the second-phase structure. In a composite structure sheet steel comprising 0.02 to 0.12% C, 0.5 to 2.0% Si+Al and 1.0 to 2.0% Mn, with the remainder being Fe and unavoidable impurities, and comprising 80% or more polygonal ferrite (steel structure space factor) and 1 to 7% retained austenite, with the remainder being bainite and/or martensite, wherein the elongation and stretch flange formability of the composite sheet steel are improved by reducing the number of bulky, massive second phases with an aspect ratio of 1:3 or less and a mean grain size of 0.5 μm or more in the second phase of this composite structure, which comprises retained austenite and martensite.