B - Operations – Transporting – 21 – F
Patent
B - Operations, Transporting
21
F
148/34.6
B21F 3/00 (2006.01) C21D 8/06 (2006.01) C21D 9/02 (2006.01)
Patent
CA 2002138
TITLE OF THE INVENTION HIGH-STRENGTH COIL SPRING AND METHOD OF PRODUCING SAME ABSTRACT OF THE DISCLOSURE 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 µm, so that not only it has been impossible to remove surface defects having a surface rough- ness of 6 to 20 µm 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 producing the same.
Shibata Takeshi
Yamamoto Susumu
Riches Mckenzie & Herbert Llp
Sumitomo Electric Industries Ltd.
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