| 摘要 |
A gear is manufactured using raw material steel having the following chemical composition: C: 0.1% to 0.40% (% by mass), Si: 0.35% to 3.0%, Mn: 0.1% to 3.0%, Cr: less than 0.2%, Mo: 0.1% or less, P: 0.03% or less, S: 0.15% or less, Al: 0.05% or less, N: 0.03% or less, and Fe and unavoidable impurities: remainder, and by performing: a carburizing process of forming a carburized layer on a surface of the gear at a low oxygen concentration, a cooling process of cooling the gear after the carburizing process at a low cooling rate at which no martensite transformation takes place, to or below a temperature at which structural transformation is completed, and a quenching process of heating the gear by high-density energy heating after the cooling process so as to austenitize a region lying shallower than a core portion and tooth portions without austenitizing the core portion, and rapidly cooling the gear from that state. Consequently, surface layer portions of the tooth portions and a tooth root portion are made to be a carburized layer, the remaining portion of the tooth portions and a portion of a disk portion lying below the carburized layer be a quench-hardened layer, and a region of the disk portion lying deeper than the quench-hardened layer be an unquenched layer. |
