冷間工具鋼の諸特性に及ぼすHV1200級Fe-Cr-B投射材を用いたショットピーニングの影響

摘要

Shot peening is widely used for automobile parts such as springs and gears to improve fatigue strength. In general, high-hardness media is required for shot peening to high-hardness materials. Recently, shot peening to various tool steels such as cold and hot work tool steels and high speed tool steel has been investigated and is used in some applications, and improvements in fatigue strength and die life by the increase of compressive residual stress and hardness at their shot peened surface have been reported. In this study, the properties of cold work tool steel shot peened by Fe-8%Cr-6.5%B (mass%) gas atomized powder (FeCrB powder) with HV 1200-class Vickers hardness and long life as shot peening media were examined. Quenched and tempered JIS SKD11 followed by shot peening by FeCrB and high speed steel powder sieved between 45 and 125 μm was used. Vickers hardness and compressive residual stress of the shot peened JIS SKD11 surface by FeCrB powder were higher than these by high speed steel powder. As a result, JIS SKD11 shot peened by FeCrB powder showed excellent fatigue property, Charpy impact value and wear resistance property.%ショットピーニソグは投射材と呼ばれる金属やセラミックスの粉末を，被処理材に噴射，衝突させることにより，被処理材の表面に圧縮残留応力を付与する冷間加工の一種である.表面に圧縮残留応力が付与された部品は疲労強度が向上するため，ショットピーニングは自動車用バネやギヤなどに広く用いられている．また，冷間工具鋼，熱間工具鋼および高速度工具鋼のように硬度の高い被処理材へのショットピーニングも研究，適用されている．