G0400401 ばね鋼の疲労強度に及ぼす硬質マイクロショットピーニングの影響

Abstract

In shot peening, the surface of the material receives a so-called peening effect where strong local deformation forms a work-hardened layer or causes compressive residual stress. More recently, a new type of microshot has been developed to enhance the peening effect. In the present study, the effect of microshot peening on the surface characteristics and fatigue strength of spring steel was investigated. The workpiece was commercial spring steel SUP9. In the microshot peening process, the equipment was used an air-type machine. The microshots used were high-carbon cast steel and cemented carbide with an average diameter of 0.1mm. Air pressure was 0.6 MPa and peening time was in the range of 10-100s. Surface roughness and Vickers hardness for the peened workpiece were measured. The out-of-plane bending fatigue tests were also carried at a frequency of 200 rpm. As the peening time increased, surface roughness for the peened workpiece decreased. The use of microshot was the very effective means of reducing surface defect. The microshot peening process was very efficient in improving the fatigue life of spring steel, especially at a high number of cycles. It was found that the use of the hard microshot was found to cause a significantly enhanced peening effect for spring steel.