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:
Feb. 03, 2009
Filed:
May. 23, 2002
Tetsuya Mega, Tokyo, JP;
Kei Sakata, Tokyo, JP;
Tetsuya Mega, Tokyo, JP;
Kei Sakata, Tokyo, JP;
JFE Steel Corporation, , JP;
Abstract
This disclosure proposes a high-strength hot rolled steel sheet having excellent anti-die-galling property and anti-fatigue property, in which the steel sheet has a composition including C: not less than 0.02 mass % but not more than 0.2 mass %, Si: not less than 0.2 mass % but not more than 1.2 mass %, Mn: not less than 1.0 mass % but not more than 3.0 mass %, Mo: not less than 0.1 mass % but not more than 1.0 mass %, Al: not less than 0.01 mass % but not more than 0.1 mass %, P: not more than 0.03 mass % S: not more than 0.01 mass % and the remainder being substantially Fe and inevitable impurities, and has a steel microstructure containing not less than 55 vol % of ferrite and not less than 10 vol % but not more than 40 vol % of martensite provided that a total of both is not less than 95 vol %, and a ratio ds/dc of an average crystal grain size ds of the ferrite in a surface layer portion of the steel sheet to an average crystal grain size dc of the ferrite in a center portion of the steel sheet is 0.3<ds/dc≦1.0 and a surface roughness is not more than 1.5 μm as an arithmetic mean roughness Ra, as well as a method of producing the same.