| 摘要 |
PROBLEM TO BE SOLVED: To improve the strength and life of a joint cross while maintaining its price. SOLUTION: The joint cross 4 is composed of boron-titanium steel where chromium steel is used as a base and boron(B) and titanium(Ti) are properly added, and carburizing treatment is applied to the cross joint, by which the ratio of carburizing depth (h) to the radius (r) at shaft ends 4a-4d, h/r, is set at 5-20% and also austenite grain size is set to >=#10. By this method, static strength, fatigue strength and rolling life can be improved while maintaining the price as compared with the conventional case where chromium-molybdenum steel is used.
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