Outer race for constant velocity joint, having improved anti-flaking properties and shaft strength, and process for producing the same

A process for producing an outer race for a constant velocity joint, including a cup and an involute serration and having improved anti-flaking properties and shaft strength, said process comprising the steps of:

• subjecting a steel comprising by weight
• carbon:
• 0.45 to 0.59%,
• silicon:
• 0.15 to 0.4%,
• manganese:
• 0.15 to 0.45%,
• sulfur:
• 0.005 to 0.15%,
• molybdenum:
• 0.1 to 0.35%,
• boron:
• 0.0005 to 0.005%,
• aluminum:
• 0.015 to 0.05%, and
• titanium:
• 0.015 to 0.03% and, in addition,
• nitrogen:
• limited to not more than 0.005% (inclusive of 0%),
• chromium:
• limited to not more than 0.1% (inclusive of 0%),
• phosphorus:
• limited to not more than 0.02% (inclusive of 0%), and
• oxygen:
• limited to not more than 0.002% (inclusive of 0%),
• with the balance consisting of iron and unavoidable impurities,
• to annealing, cold forging, machining, and form rolling to form an outer race having a predetermined shape;
• and
• then induction hardening the outer race in its shaft including the inner surface of the cup and the involute serration, followed by tempering, thereby producing an outer race for a constant velocity joint that the proportion of the effective case depth in track grooves of the cup is 0.25 to 0.45 in terms of the ratio of the effective case depth t to the wall thickness of the cup w, t/w, and the proportion of the effective case depth of the involute serration in its end is 0.20 to 0.50 in terms of the ratio of the effective case depth t to the radius r, t/r.