浸炭・鍛造焼入れによる高疲労強度傘歯車の開発

概要

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In the previous report, basic tests conducted on test pieces revealed the possibility of improvement of bevel gear strength through the combined application of carburizing and forge-quenching. A study was then made of suitable manufacturing conditions including the blank shape, die shape and forging temperature, and metallurgical structures and mechanical properties were examined. The following results were obtained in carburized, forge-quenched gears and bevel gears that were by conventional process. (1) Bevel gear strength was reduced due to increased surface roughness as a result of oxidation when gears were forged at temperatures over 1050℃. (2) Low cycle fatigue life of the gear corner R of tooth root was 100 times longer at a forging temperature of 1050℃, but 40 times longer at forging temperatures of 850 or 950℃. (3) The bending fatigue limit of the corner R of tooth root was 40% higher at a forging temperature of 850℃, but 20% higher at 1050℃. (4) Gear accuracy was nearly equal to that of gears manufactured by a conventional machining process. The results of these tests have led to the development of higher fatigue strength bevel gears.
1992-08-01