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:
Jul. 29, 2008
Filed:
Jan. 24, 2002
Hiromu Izumida, Itami, JP;
Nozomu Kawabe, Itami, JP;
Teruyuki Murai, Itami, JP;
Sumitomo Electric Industries, Ltd., Osaka, JP;
Abstract
A high-strength steel wire for heat-resistant springs has both excellent high-temperature tensile strength and excellent high-temperature sag resistance at a temperature as high as 350 to 500° C., particularly at 400° C. or so (these properties are needed for spring materials). The steel wire contains (a) 0.01 to 0.08 wt % C, 0.18 to 0.25 wt % N, 0.5 to 4.0 wt % Mn, 16 to 20 wt % Cr, and 8.0 to 10.5 wt % Ni, (b) at least one constituent selected from the group consisting of 0.1 to 3.0 wt % Mo, 0.1 to 2.0 wt % Nb, 0.1 to 2.0 wt % Ti and 0.3 to 2.0 wt % Si, and (c) mainly Fe and unavoidable impurities both of which constitute the remainder. The steel wire has (a) a tensile strength of at least 1,300 N/mmand less than 2,000 N/mmbefore being treated with low-temperature annealing, and (b) a maximum crystal-grain diameter of less than 12 μm in the γ phase (austenite) in a transverse cross section of the wire.