Inducing High Residual Stress Through Shot Peening with High Hardness Conditioned Cut Wire

Author:  Hayato Taniguchi, Daisuke Gowa
Source:  ICSP-13
Doc ID:  2017052
Year of Publication:  2017
Introduction: Currently, the automobile industry has adopted shot peening methods for automotive parts such as transmission gear, spring, and engine parts. As it is now, the shot peening method is used for almost all parts. Materials and heat-treatment for shot peening have evolved to apply static strength and fatigue strength. An effect required of shot peening is mainly fatigue strength improvement, and this effect depends on compression residual stress. Naturally, optimum shot and conditions should be selected by considering the mechanical properties of the product. With social conditions changing, the automobile industry has been required to reduce the emission of CO2 because of international efforts to reduce CO2 [1]. It is an especially important issue. For that reason, the vacuum carburized furnace has been selected to replace the gas carburized furnace, because it has low CO2 emission [2]. Normally, less than 700HV hardness shot media is used for gas carburized parts. On the other hand, the surface hardness of vacuum carburized parts is approximately 800HV. But the difference in hardness is not considered as a criteria for shot peening. In most cases, the same shot peening conditions are used as with vacuum carburized parts, but actually, shot media that is harder than the processing object should be used. Therefore, high hardness conditioned cut wire has been developed for harder products like vacuum carburized parts. In this study, it is shown that high hardness conditioned cut wire can induce higher residual stress compared to existing conditioned cut wire.

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