| 摘要 |
A spring with superior fatigue resistance and a production method therefor are provided by decreasing the material cost and simplifying the production process. There is provided with a spring comprising: a composition consisting of, by mass %, 0.5 to 0.7 % of C, 1.0 to 2.0 % of Si, 0.1 to 1.0 % of Mn, 0.1 to 1.0 % of Cr, not more than 0.035 % of P, not more than 0.035 % of S, and the balance of Fe and inevitable impurities; a structure including not less than 95 % of tempered martensitic structure by area ratio in a cross section of a wire material; a compressive residual stress layer formed from a surface to a depth of 0.35 mm to D/4, in which D (mm) is a circle-equivalent diameter of a cross section, the compressive residual stress layer having maximum compressive residual stress of 800 to 2000 MPa; a center portion with Vickers hardness of 550 to 700 HV in the cross section; and a high hardness layer with greater hardness than the center portion by 50 to 500 HV from a surface to a depth of 0.05 to 0.3 mm. |
