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Title:
SPRING OF EXCELLENT FATIGUE RESISTING CHARACTERISTICS AND SURFACE TREATMENT METHOD FOR MANUFACTURING THE SAME
Document Type and Number:
WIPO Patent Application WO/2000/049186
Kind Code:
A1
Abstract:
A surface treatment method for manufacturing springs of excellent fatigue resisting characteristics, comprising: projecting hard metal particles 500-900 $g(m) in particle diameter which are softer than a nitrided outermost layer of a spring, and which have a hardness Hv of 500-800, onto an outer surface of the nitrided spring at 40-90 m/sec with the occurrence of fine cracks in an outer layer thereof being prevented, whereby residual compressive stress due to the projection operation is applied up to a comparatively deep inner portion of the spring; and projecting onto the surface of the same spring a large number of fine metal particles having an average particle diameter of not smaller than 10 $g(m) and larger than 100 $g(m), a spherical shape or a shape near a spherical shape with no angular portions, a specific gravity of 7.0-9.0, and a hardness Hv which is not lower than 600 and not higher than 1100 and which is not higher than the hardness of the outermost layer of the nitrided spring, at 50-190 m/sec while being controlled to a temperature which causes work hardening to occur in the outer layer of the spring but which is lower than a level at which the softening of the outer layer due to the recovery recrystallization thereof occurs, whereby a high residual compressive stress is applied to a portion very close to the outer surface of the spring without causing fine cracks to occur in the outer layer thereof, this enabling a valve spring of a high fatigue strength to be obtained.

Inventors:
ISHIDA MASAAKI (JP)
UZUMAKI KAZUHIRO (JP)
ISONO YUJI (JP)
TERATOKO KEIICHIRO (JP)
YAMADA YOSHIRO (JP)
SUZUKI HIROSHI (JP)
SASADA HIRONOBU (JP)
Application Number:
PCT/JP1999/004539
Publication Date:
August 24, 2000
Filing Date:
August 23, 1999
Export Citation:
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Assignee:
SUNCALL CORP (JP)
ISHIDA MASAAKI (JP)
UZUMAKI KAZUHIRO (JP)
ISONO YUJI (JP)
TERATOKO KEIICHIRO (JP)
YAMADA YOSHIRO (JP)
SUZUKI HIROSHI (JP)
SASADA HIRONOBU (JP)
International Classes:
B24C1/10; C21D7/06; (IPC1-7): C21D7/06; B24C1/10
Foreign References:
JPH09279229A1997-10-28
JPH05339628A1993-12-21
JPH0957629A1997-03-04
JPH05140726A1993-06-08
Attorney, Agent or Firm:
Ehara, Syogo (Edobori 1-chome Nishi-ku, Osaka-shi Osaka, JP)
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