| 摘要 |
PROBLEM TO BE SOLVED: To provide a rolled steel for cold forging/nitriding, capable of being subjected to cold forging without performing heat treatment beforehand, having reduced surface roughness after cold forging, having excellent machinability after cold forging and capable of imparting high core part hardness to a component subjected to cold forging and nitriding.SOLUTION: A rolled steel for cold forging/nitriding has a chemical composition including 0.06 to 0.15% C, 0.02 to 0.35% Si, 0.10 to 0.90% Mn, ≤0.030% S, 0.50 to 2.0% Cr, 0.10 to 0.50% V and 0.010 to 0.090% Al, and the balance Fe with impurities; wherein P, N and O in the impurities satisfy P≤0.030%, N≤0.0080% and O≤0.0030%, and 5.0≤35(C+N)+5(Si+Mn)+Cr+3(Cu+Ni)+4(Mo+V)≤10.0 and 1.8≤{V+(9/20)Mo}/C≤9.0 is satisfied. The rolled steel for cold forging/nitriding has a microstructure of ferrite-pearlite structure, in which the average grain size of the ferrite is ≤50 μmn. |
