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. 13, 2011
Filed:
Dec. 27, 2006
Koichi Nakagawa, Kanagawa, JP;
Reiko Sugihara, Chiba, JP;
Tetsuo Shimizu, Chiba, JP;
Shusaku Takagi, Hiroshima, JP;
Koichi Nakagawa, Kanagawa, JP;
Reiko Sugihara, Chiba, JP;
Tetsuo Shimizu, Chiba, JP;
Shusaku Takagi, Hiroshima, JP;
JFE Steel Corporation, Tokyo, JP;
Abstract
A hot-rolled high strength steel sheet in which, without using expensive Mo, and by effectively using Ti, which is an expensive element, the amount of precipitation hardening of which is large, both ductility and stretch-flangeability are improved at a tensile strength of 780 MPa or higher, and desirable tensile fatigue properties are exhibited. The hot-rolled high strength steel sheet has a composition including, in percent by mass, C: 0.06% to 0.15%, Si: 1.2% or less, Mn: 0.5% to 1.6%, P: 0.04% or less, S: 0.005% or less, Al: 0.05% or less, and Ti: 0.03% to 0.20%, the balance being Fe and incidental impurities, wherein the steel sheet has a structure in which the volume fraction of ferrite is 50% to 90%, the balance is substantially bainite, the total volume fraction of ferrite and bainite is 95% or more, precipitates containing Ti are precipitated in the ferrite, and the precipitates have an average diameter of 20 nm or less; and 80% or more of the Ti content in the steel is precipitated.