| 摘要 |
PROBLEM TO BE SOLVED: To find out carbon concentration and nitrogen concentration in a surface layer effective for improving fatigue strength; and to find out an amount of residual austenite optimum for applying compressive residual stress and improving hardness by inductive-transforming of residual austenite by shot-peening after carbo-nitriding. SOLUTION: In the ball screw 100 comprising a screw shaft 110 having a screw groove on an outer periphery, a nut 120 having a screw groove on an inner periphery, and a steel ball assembled in the screw grooves of the screw shaft 110 and the nut 120, the steel ball has the carbon concentration of 1.1 to 1.3 wt.% on the surface layer, the nitrogen concentration of 0.1 to 0.35 wt.%, and the residual austenite amount of 10 to 30 vol.%. COPYRIGHT: (C)2006,JPO&NCIPI
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