| 摘要 |
PROBLEM TO BE SOLVED: To provide hot-forged parts that have a fatigue strength exceeding 350 MPa and an endurance ratio of 0.45 or higher in a portion of a base metal, which receives no influence even after having been subjected to an induction hardening step, and that hardly cause hardening crack due to induction hardening. SOLUTION: The hot-forged parts comprise 0.35-0.58% C, 0.10-1.00% Si, 0.50-1.50% Mn, 0.030% or less P, 0.020-0.130% S, 0.03-0.30% Cr, one or more elements of V, Nb and Ti in an amount of 0.03-0.30% in total and the balance Fe with impurities; and satisfy the expressions of fn1≥8.0 and fn2≥300. Here, fn1=S<SP>-0.59</SP>×RA<SP>-2.1</SP>×24,500 and fn2=521-353C-22Si-25Mn-8Cu-17Ni-18Cr-26Mo, wherein S, C, Si, Mn, Cu, Ni, Cr and Mo represent mass% of each element; and RA represents a total reduction (%) of an area during the hot working step in a hot forging process for forming the steel ingot into the final parts. COPYRIGHT: (C)2007,JPO&INPIT
|
