To provide a ball screw device capable of having an excellent wear resistance and being suitably used even when a high load is applied momentarily and in a short stroke service condition.
At least a screw shaft 1 of the ball screw device is formed of an alloy steel containing C of 0.15 to 0.6 wt%, Si of 0.1 to 0.9 wt%, Mn of 0.1 to 1.5 wt%, and Cr of 0.5 to 4.0 wt%. In an exterior thread groove 2 of the screw shaft 1 complete after carbonizing or carbonitrizing, a total area ratio of carbide, nitride and carbonitride (hereinafter referred to as carbide, etc.) in the range from the surface to 50μm is 10% to 30%, and an area ratio of carbide, etc. with grain diameter of 1μm or less is the total area of 60% or more. Vickers hardness in the range of the rolling element diameter of 2% from the surface is Hv 700 or more, and the maximum grain diameter of the carbide, etc. is 5μm or less in a circle equivalent diameter.
Yoshiaki Naito
Cui Shu Tetsu
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