| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an induction-hardened gear excellent in inner hardness, toughness and surface fatigue strength, and an induction hardening method of a gear.SOLUTION: The induction-hardened gear is provided which is made of a steel composed of V of 0.05 to 0.35% and other predetermined component composition, and in which a depth of hardened region of a martensite structure is 0.3 to 3.0 mm, hardness at a position of 50μm depth from a surface is HV 620 to 850, a minimum value at a side closest to the hardened region in a hardness distribution in an inner region from a position of depth of the hardened region is HV300 to 550, and in terms of a prior austenite grain at a position of 50μm from the surface, no mixed particle having average diameter of 5μm or less and defined by JIS G 0551 is not present. The induction hardening method of a gear is also provided which performs heat treatment by induction hardening twice and comprises a first heat treatment and a second heat treatment consisting of preliminary heating and main heating, each of the heat treatment having a predetermined temperature pattern.</p> |
