Patent ID: 8328956

Claim:
A carbonitrided induction hardened steel part superior in surface fatigue strength at high temperature comprising steel, the steel comprising, by mass %, C: 0.005 to 0.22%, Si: 2.0% or less, Mn: 0.2 to 3.0%, P: 0.03% or less, S: 0.005 to 0.10%, Ni: 3.0% or less (including 0%), Cr: 5.0% or less (including 0%), Mo: 2.0% or less (including 0%), W: 1.0% or less (including 0%), B: 0.0050% or less (including 0%), O: 0.0050% or less, and N: 0.003 to 0.03%, one or both of Al: 0.005 to 0.2% and Ti: 0.005 to 0.2% and one or both of V: 0.3% or less and Nb: 0.3% or less, and a balance of iron and unavoidable impurities, wherein the steel part is carbonitrided, and then induction hardened, and wherein the steel part has a surface N concentration of 0.1 to 0.8 mass %, a sum of N and C concentrations of 1.0 to 2.0 mass %, a surface residual austenite in an amount of less than 10 vol %, an incompletely hardened layer at a depth from the surface of less than 5 μm, and a surface X-ray diffraction half width of 6.0 degrees or more.