SPRING AND METHOD FOR PRODUCING SAME

摘要

Provided are: a spring that has a high compressive residual stress layer having increased fatigue resistance and that has increased simplicity of the production process and decreased materials cost; and a method for producing the spring. The following are performed in order: a formation step for forming a spring shape in a steel material having the components by mass% of 0.5-0.7% of C, 1.0-2.0% of Si, 0.1-1.0% of Mn, 0.1-1.0% of Cr, no greater than 0.035% of P, and no greater than 0.035% of S, the remainder comprising iron and unavoidable impurities; a heat treatment step for austenitizing at a temperature of the Ac3 point to (Ac3 point + 250°C), then cooling at a rate of at least 20°C/second, isothermally holding for at least 400 seconds at a temperature of (Ms point - 20°C) to (Ms point + 60°C), and then cooling to room temperature at a cooling rate of at least 20°C/second; a setting step for imparting a permanent strain; and a shot peening step for projecting shot.