Abstract: Disclosed are an outer race for a constant velocity joint, having improved anti-flaking properties and shaft strength, and a process for producing the same. The outer race for a constant velocity joint includes a cup and a serration and comprises 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%, the proportion of the effective case depth in track grooves of the cup being 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, the proportion of the effective case depth of the involute serration in its end being 0.20 to 0.50 in terms of the ratio of the effective case depth t to the radius r, t/r. The involute serration in its end preferably has a former austenite grain size of not less than 8 in terms of the grain size number specified in JIS (Japanese Industrial Standards).

Abstract: Disclosed are a high strength drive shaft and a process for producing the same. The high strength drive shaft comprises as a steel material, by weight, carbon: 0.48 to 0.58%, silicon: 0.01 to 0.15%, manganese: 0.35 to 0.75%, 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: 0.02 to 0.08%, the proportion of the effective case depth of an involute serration in its end of the drive shaft being 0.3 to 0.7 in terms of the ratio of the effective case depth t to the radius r, t/r. The involute serration in its end preferably has a former austenite grain size of not less than 8 in terms of the grain size number specified in JIS (Japanese Industrial Standards). A steel comprising the above constituents and having a hardness of 85 to 95 HRB is machined and form rolled into a shaft, and the shaft is induction hardened and then tempered at 120 to 200° C. to produce the high strength drive shaft.

Abstract: Disclosed is a process for producing a shaft having improved strength without sacrificing machinability and cold workability. The process for producing a high strength shaft comprises the steps of: rolling or forging an alloy at a heating temperature of Ac3 to 105° C. with a reduction in area of not less than 30%, the alloy comprising by weight carbon: 0.47 to 0.55%, silicon: 0.03 to 0.15%, manganese: 0.20 to 0.50%, molybdenum: 0.08 to 0.30%, sulfur: 0.005 to 0.035%, boron: 0.0005 to 0.005%, titanium: 0.05 to 0.20%, nitrogen: not more than 0.01%, aluminum: 0.005 to 0.05%, and manganese+molybdenum: 0.45 to 0.70% with the balance consisting of iron and unavoidable impurities, thereby producing a steel product having a hardness after rolling or forging of 85 to 97 HRB; and induction hardening the steel product to obtain a shaft, as shown in FIG. 1, having a hardening depth ratio (distance from the surface to a position of 500 HV/radius of component) of not less than 0.

Abstract: The process for producing a constant velocity joint having improved cold workability, rolling fatigue life, and torsional strength comprises the steps of: rolling or forging an alloy at a heating temperature of Ac.sub.3 to 1000.degree. C. with a reduction in area of not less than 30%, said alloy comprising by weight carbon: 0.52 to 0.60%, silicon: 0.03 to 0.15%, manganese: 0.10 to 0.40%, chromium: 0.05 to 0.30%, molybdenum: 0.10 to 0.30%, sulfur: 0.003 to 0.020%, boron: 0.0005 to 0.005%, titanium: 0.02 to 0.05%, nitrogen: not more than 0.01%, aluminum: 0.005 to 0.05%, and manganese+chromium+molybdenum: 0.35 to 0.80% with the balance consisting of iron and unavoidable impurities; spheroidizing the rolled or forged alloy in such a manner that, after heating to Ac.sub.1 to 770.degree. C., slow cooling is performed from 730.degree. C. to 700.degree. C. at a rate of not more than 15.degree. C.

Abstract: A carbon steel useful for machine structural use having improved cold forgability and induction hardenability comprises particular amounts of C, Si, Mn, Cr, S, P, O, N or further Mo and the balance being substantially Fe.