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. 05, 2008
Filed:
Mar. 23, 2005
Hidetoshi Yoshikawa, Nagoya, JP;
Tomohiro Nakano, Nagoya, JP;
Takayuki Sakakibara, Nagoya, JP;
Masami Wakita, Nagoya, JP;
Hidetoshi Yoshikawa, Nagoya, JP;
Tomohiro Nakano, Nagoya, JP;
Takayuki Sakakibara, Nagoya, JP;
Masami Wakita, Nagoya, JP;
Chuo Hatsujo Kabushiki Kaisha, Nagoya, JP;
Abstract
An oil-tempered wire for a cold-formed coil spring having a quality equivalent of or higher than a hot-formed coil spring is provided. A cold-formed coil spring made from the oil-tempered wire is also provided. Material used is the steel which contains, in weight percentage, 0.35 to 0.55% C, 1.8 to 3.0% Si, 0.5 to 1.5% Mn, 0.5 to 3.0% Ni, and 0.1 to 1.5% Cr. The ferrite fraction in the microscopic structure of this material is set to 50% or less. Hot rolled wire is cold drawn with a predetermined reduction of area, and a heat treatment using high frequency induction heating is conducted. It is preferable to set the maximum heating temperature between 900° C. to 1020° C. (favorably 950° C.) and holding time between 5 to 20 seconds. It is preferable to make the oil tempered material to have the grain size number of 9 or more, and the tensile strength from 1830 to 1980 MPa.