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:
Jun. 12, 2012
Filed:
Jun. 04, 2007
Michiharu Nakaya, Kakogawa, JP;
Yoichi Mukai, Kakogawa, JP;
Koichi Sugimoto, Nagano, JP;
Kobe Steel, Ltd., Kobe-shi, JP;
Abstract
The present invention provides a high-strength steel sheet which has a 980 MPa class tensile strength as well as has excellent elongation, stretch flangeability and weldability, and also has excellent anti-delayed fraction property. The high-strength steel sheet comprises steel satisfying: C: 0.12 to 0.25%, Si: 1.0 to 3.0%, Mn: 1.5 to 3.0%, P: 0.15% or less, S: 0.02% or less, Al: 0.4% or less, and comprising the remnant made from iron and unavoidable impurities, wherein a ratio of the contents of Si and C (Si/C) is within the range from 7 to 14 in terms of a mass ratio, and a microstructure in a longitudinal section comprises, by an occupancy ratio based on the entire structure, 1) bainitic ferrite: 50% or more, 2) lath-type residual austenite: 3% or more, and 3) block-type residual austenite: 1% or more to ½×occupancy ratio of lath-type residual austenite, and 4) average size of block-type second phase is 10 μm or less.