| 摘要 |
A mechanical structural component is a toothed component obtained by performing cold forging and carburizing treatment on a steel having a chemical composition that includes, in % by mass: 0.10% to 0.35% C; 0.01% to 0.13% Si; 0.30% to 0.80% Mn; 0.03% or less P; 0.03% or less S; 0.01% to 0.045% Al; 0.5% to 3.0% Cr; 0.0005% to 0.0040% B; 0.003% to 0.080% Nb; and 0.0080% or less N, wherein Ti mixed in the chemical composition as an impurity is limited to 0.005% or less, and the chemical composition has a balance including Fe and incidental impurities, in prior austenite grains after the carburizing treatment, an area ratio of crystal grains of 50 µm or less is 80% or more, and an area ratio of crystal grains exceeding 300 µm is 10% or less, and a total helix deviation of teeth after the carburizing treatment satisfies Formula (1) B max / L × 10 3 ‰¤ 5 where B max is a maximum total helix deviation in all teeth in mm, and L is a face width in mm. Such a toothed mechanical structural component has excellent dimensional accuracy. |
