US 11,807,923 B2
Spring steel wire
Hiromu Izumida, Osaka (JP); and Tetsuya Nakajima, Osaka (JP)
Assigned to Sumitomo Electric Industries, Ltd., Osaka (JP)
Appl. No. 17/058,459
Filed by Sumitomo Electric Industries, Ltd., Osaka (JP)
PCT Filed Jun. 17, 2020, PCT No. PCT/JP2020/023718
§ 371(c)(1), (2) Date Nov. 24, 2020,
PCT Pub. No. WO2021/255848, PCT Pub. Date Dec. 23, 2021.
Prior Publication US 2022/0186349 A1, Jun. 16, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/18 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01)
CPC C22C 38/18 (2013.01) [C22C 38/02 (2013.01); C22C 38/04 (2013.01); C21D 2211/008 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A spring steel wire comprising:
a main body made of a steel and having a line shape; and
an oxidized layer covering an outer peripheral surface of the main body;
the steel constituting the main body containing not less than 0.62 mass % and not more than 0.68 mass % C, not less than 1.6 mass % and not more than 2 mass % Si, not less than 0.2 mass % and not more than 0.5 mass % Mn, not less than 1.7 mass % and not more than 2 mass % Cr, and not less than 0.15 mass % and not more than 0.25 mass % V, with the balance being Fe and unavoidable impurities, a value obtained by dividing a sum of a Si content and a Mn content by a Cr content being not less than 0.9 and not more than 1.4,
the steel constituting the main body having a tempered martensite structure;
wherein the oxidized layer contains Fe3O4 in a percentage of not less than 80 mass %, and
wherein the oxidized layer has thickness of not less than 2 μm and not more than 5 μm.