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. 18, 2009
Filed:
Feb. 07, 2002
Masayuki Hashimura, Muroran, JP;
Takanari Miyaki, Muroran, JP;
Hiroshi Hagiwara, Chiyoda-ku, JP;
Hiroaki Hayashi, Chiyoda-ku, JP;
Shouich Suzuki, Chiyoda-ku, JP;
Katsuaki Shiiki, Wako, JP;
Noriyuki Yamada, Wako, JP;
Seiichi Koike, Wako, JP;
Masayuki Hashimura, Muroran, JP;
Takanari Miyaki, Muroran, JP;
Hiroshi Hagiwara, Chiyoda-ku, JP;
Hiroaki Hayashi, Chiyoda-ku, JP;
Shouich Suzuki, Chiyoda-ku, JP;
Katsuaki Shiiki, Wako, JP;
Noriyuki Yamada, Wako, JP;
Seiichi Koike, Wako, JP;
Nippon Steel Corporation, Tokyo, JP;
Abstract
The present invention provides a steel wire, for springs excellent in coiling property while having a high strength, as a heat treated steel wire for high strength springs, characterized by: comprising, in mass, C: 0.75 to 0.85%, Si: 1.5 to 2.5%, Mn: 0.5 to 1.0%, Cr: 0.3 to 1.0%, P: not more than 0.015%, S: not more than 0.015%, N: 0.001 to 0.007%, W: 0.05 to 0.3%, and the balance consisting of Fe and unavoidable impurities; having a tensile strength of not less than 2,000 MPa; spheroidal carbides, composed of mainly cementite, observed in a microscopic visual field satisfying the area percentage of the spheroidal carbides not less than 0.2 μm in circle equivalent diameter being not more than 7%, the density of the spheroidal carbides 0.2 to 3 μm in circle equivalent diameter being not more than 1 piece/μm, and the density of the spheroidal carbides over 3 μm in circle equivalent diameter being not more than 0.001 piece/μm; the prior austenite grain size number being #10 or larger; the content of the retained austenite being not more than 12 mass %; the maximum diameter of carbides being not more than 15 μm; and the maximum diameter of oxides being not more than 15 μm.