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:
Mar. 07, 2006
Filed:
Jul. 09, 2003
Hiroshi Akamizu, Kobe, JP;
Shushi Ikeda, Kobe, JP;
Koichi Makii, Kobe, JP;
Abstract
A high-strength steel sheet comprises carbon: 0.06 to 0.25 mass %, Si: 0.5 to 3.5 mass % and Mn: 0.7 to 4 mass %. Its mother structure is ferrite, its second phase structure comprises martensite and the residual austenite and the second phase structure measured by image analysis has an area fraction of 25% or less based on the total structure. The steel sheet satisfies the following requirements (1) to (3): (1) the volume fraction (Vtγhd R) of the residual austenite is 5% or more; (2) the ratio (SFγ/Vtγ) of the area fraction (SFγ) of the residual austenite within ferrite to Vtγis 0.65 or more; and (3) the ratio [α2/(α1+γ)] of the space factor (α2) of martensite to the second phase structure (α1+γ) is 0.25 to 0.60. The steel sheet has excellent balance between strength and local elongation, and a low yield ratio.