Process for producing high-strength spring

Abstract

The present invention provides a process for producing a high-strength spring capable of having a compressive residual stress greater than in the prior art. In particular, the process comprises subjecting to shotpeening a spring having undergone final heating, such as tempering (for heat-treated spring) or stress relieving annealing (for cold formed spring), while the surface temperature of the spring is in the range of 265 to 340 DEG C (preferably 300 to 340 DEG C). The spring after shotpeening is quenched. It is preferred that setting be performed prior to shotpeening, or after shotpeening but before quenching. The quenching can be accomplished by water cooling or oil cooling with no preference. When the wire diameter of the spring is small, forced air cooling can be used.

Description

technical field The present invention relates to a shot peening method for producing springs, especially suspension springs, which have a high level of durability (or fatigue resistance) and sag resistance. Background technique As a method for significantly improving spring durability, shot peening is an indispensable method for high-strength springs, especially for suspension springs used in automobiles or valve springs used in engines. In the shot peening method, a large number of small particles are projected onto the surface of a target object. The process is superficially the same as shot blasting, which removes burrs (or knurling) from cutting or forming the article, or scale (ie, a hard oxide layer) from heat treatment. Surface cleaning process. However, the two processes differ significantly from each other in terms of strength and other conditions; for shot peening, the determined condition is that the plastic deformation is only on the surface of the spring, so...

AI Technical Summary

Problems solved by technology

These past technologies have not always met the performance requirements of the latest springs applied at higher levels of operating stress

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