PURPOSE: To suitably improve the fatigue strength of a steel pipe for use in hollow axle by grinding-machining the inner face of the steel pipe by 10 to 1200μm.
CONSTITUTION: With a steel pipe for use in driving hollow axle, the inner face of the steel pipe is ground and machined by 10μm or more to grind and remove one or two or more of irregularities, flaws or decarburized layer to improve the fatigue strength property. The metal-removal rate is changed depending on the inner bore diameter of the hollow axle. In the case of this type of hollow axle, the upper limit of metal removal rate is 1200μm. The grinding process is relatively simple and low-priced, and the wall-thinning for grinding-machining is limited to maintain the strength property.
FUKUI TOSHIHIKO
ISHIZAWA YOSHIKAZU
KONDO RYUICHI
