超硬ショットの特性とばねへの応用
1998 年 1998 巻 43 号 p. 23-30
詳細
1998 年 1998 巻 43 号 p. 23-30
There is an urgent need automotive springs with high fatigue strength, which enable fuel efficiency improvement, vehicle weight reduction and higher output. To realize this, spring materials of higher strengths are sought, and formed spring surface is often hardened.
Due to this trend, spring materials with much higher strength than previously, are being used. Also, formed springs receive extreme surface hardening, to over 900 HV in some cases. Conventional shot peening media are not effective enough to peen such ultra-hard springs.
As a solution to this problem, we have developed cemented-carbide shots. This new shot medium has been applied to spring products, to established the following facts:
1) Cemented-carbide shots, with remarkable hardness and very high density, provide an enormous residual compression-stress, which would be better than any conventional shot medium. The effects of this are more evident in harder workpieces.
2) Compare to conventional shot media, the same residual compression-stress can be obtained at a lower peening speed (pressure). This results in less shot-media and equipment wear as well as lower power demand.
3) The cemented-carbide shots are especially effective for improving the fatigue strength of surface-hardened, for example gas-nitrided, springs.
