302 高靱性ばね鋼の疲労特性に及ぼすマイクロショットピーニングの影響(塑性加工とその周辺技術(1),ものづくりにおける基礎研究と先端技術の融合)

概要

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Shot peening is a surface treatment that improves the performance of engineering components. In conventional shot peening, the medium consists of small spheres, which are usually made of high-carbon cast steel; the diameter of the spheres is in the range from 0.3 to 1.2mm. More recently, however, a new type of microshot has been developed to enhance the peening effect. The diameter of the spheres in the new medium is in the range from 0.03 to 0.15mm. In the present study, the effect of microshot peening on the surface characteristics and fatigue strength of spring steel was investigated. The injection method of the microshot was of the compressed air type. The microshots of 0.1mm diameter were high-carbon cast steel and cemented carbide, and the workpiece used was the commercially spring steel JIS-SUP10. The surface roughness, hardness, compressive residual stress, and fatigue strength of the peened workpieces were measured. The surface layer of the workpieces was sufficiently deformed by microshot peening. A high hardness or residual stress was observed near the surface. The shot peening process improved the fatigue life in the high cycle range. The use of hard microshots such as cemented carbide was found to cause a significantly enhanced peening effect for spring steel.
2010-11-27