SPRING AND MANUFACTURING METHOD THEREOF

Title:

SPRING AND MANUFACTURING METHOD THEREOF

Document Type and Number:

WIPO Patent Application WO/2012/121115

Kind Code:

A1

Abstract:

Provided are a spring and a manufacturing method thereof, such that the material cost can be reduced, the manufacturing process can be simplified, and a spring excellent in fatigue endurance can be manufactured. The spring is characterized in that the spring has a composition comprising, by mass%, 0.5 - 0.7% C, 1.0 - 2.0% Si, 0.1 - 1.0% Mn, 0.1 - 1.0% Cr, 0.035% or less Cr, and 0.035% or less S, with the remainder comprising iron and unavoidable impurities; the area ratio of a tempered martensite structure is equal to or higher than 95% in an arbitrary cross-section of the coil strand; with the circle-equivalent diameter of the arbitrary cross-section being D (mm), a compressive residual stress layer is formed in the 0.35mm - D/4 range from the surface; the maximum compressive residual stress of the layer is 800 - 2,000MPa; the Vickers hardness at the center of the cross-section is 550 - 700HV; and a high-hardness layer, which is harder than the hardness at the center by 50 - 500HV, is formed in the 0.05 - 0.3mm depth range from the surface.

Inventors:

SUZUKI TAKESHI (JP)
ONO YOSHIKI (JP)
KUROKAWA SHIMPEI (JP)

Application Number:

PCT/JP2012/055277

Publication Date:

September 13, 2012

Filing Date:

March 01, 2012

Export Citation:

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Assignee:

NHK SPRING CO LTD (JP)
SUZUKI TAKESHI (JP)
ONO YOSHIKI (JP)
KUROKAWA SHIMPEI (JP)

International Classes:

C22C38/00; B21F35/00; C21D7/06; C21D9/02; C22C38/18; F16F1/02; F16F1/06

Domestic Patent References:

WO2005081586A1

2005-09-01

Foreign References:

JP2009052144A	2009-03-12
JP2007138260A	2007-06-07
JP2004346424A	2004-12-09
JP2008115468A	2008-05-22
JPS6483644A	1989-03-29
JP2008163423A	2008-07-17
JP2005120479A	2005-05-12
JPH0257637A	1990-02-27

Other References: