| abstract |
A gear which has tooth parts and tooth-root parts and which has undergone, after the forming, carburizing and quenching subsequent thereto, wherein the chemical composition of the raw material steel contains 0.10 to 0.30% of C, 0.01 to 3.00% of Ni, 0.50 to 3.00% of Si, 0.20 to 1.00% of Cr, 0.30 to 3.00% of Mn, at most 0.10% of Mo, at most 0.030% of P, at most 0.05% of N, at most 0.030% of S, and 0.01 to 1.00% of Cu with the balance being Fe and unavoidable impurities, and satisfies the relationship: Si% + Ni% + Cu% - Cr% > 0.5. Further, a tempered region which exhibits a hardness lower than that of martensite is formed by partial tempering in the surface layer in an edge part (16) in the axial end portions of the tooth and tooth-root parts, while the surface layer in the other part is composed of martensite formed by the quenching. |