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Title: High-Strength Coil Spring and Method of Producing
Author: S Yamamoto; T Shibata Itami Japan
Source: US Patent 5,152,851
Publication year 1992
Document number: 1992074
Number of pages: 11
Abstract:
The present invention relates to a high-strength coil spring useful for an engine and other high-strength springs requiring a high fatigue-resistance and a method of
producing the same.
In general, a higher tensile strength is desired for spring materials but it has been known that if a tensile strength exceeds a certain limit, a toughness and a fatigue
resistance are contrarily reduced.
In addition, a coil spring has been used after forming and then being subjected to a quenching treatment followed by being subjected to a shot peening treatment to add a
compressive residual stress to a surface thereof but an effective shot peening treatment gives a surface roughness Rmax of 6 to 20 um, so that not only it has been
impossible to remove surface defects having a surface roughness of 6 to 20 um or less but also impressions due to the shot peening have covered the surface defects to be
turned into injured portions and fatigue nuclei in many cases.
In view of the above description, the present invention has found a high-strength coil spring with high fatigue resistance using a clean steel wire, such as
chromium-vanadium steel wire and chromium-silicon steel wire, by forming it in the shape of a spring, quenching and tempering at lower temperatures to heighten the tensile
strength, and being subjected to a shot peening treatment followed by being subjected to an electrolytic polishing treatment, which does not exert a bad influence on fatigue
resistance, to remove surface defects and a method of procuding the same.
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This page last revised: 04/24/2008