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:
Oct. 25, 2011
Filed:
Mar. 16, 2006
Nao Yoshihara, Kobe, JP;
Nao Yoshihara, Kobe, JP;
Kobe Steel, Ltd., Kobe-shi, JP;
Abstract
A steel wire for a cold-formed spring according to the present invention contains a prescribed chemical component composition, wherein: a martensitic transformation start temperature Mshown by the following expression (1) is in the range from 280° C. to 380° C.; the austenite grain size number N of austenite grains is No. 12 or more; the grain boundary share of carbide precipitated along the austenite grain boundaries is 50% or less; the amount of retained austenite after austenitized and tempered is 20 vol. % or less; and the tensile strength is 2,000 MPa or more;=550−361[C]−39[Mn]−20[Cr]  (1), where [C], [Mn] and [Cr] represent the contents (mass %) of C, Mn and Cr, respectively. Such a steel wire can: secure hot-rolling formability and subsequent drawability while aiming at higher strength and higher stress; moreover exhibit excellent corrosion resistance; and obtain a spring (mainly a suspension spring for an automobile) excellent also in fatigue strength which is a basic required characteristic.