Patent ID: 8470104
Filing Date: 2013-06-25
Classification: B21F,B23P,C21D,C22C,F01L

Abstract:
1. A method of manufacturing a high strength valve spring for a vehicle engine, comprising the steps of: (a) forming a wire rod having a tensile strength of about 2200 to 2450 MPa in the form of a spring by coiling with a roller type jig; (b) cutting an end of the formed spring using a rotary type cutting blade; (c) performing residual stress removal heat treatment at about 390° C. to 410° C. for about 20 to 40 minutes; (d) performing shot peening for applying compression stress to a surface of the spring with shot balls; and (e) performing hot setting for applying, in advance, plastic deformation to the spring, wherein the step (e) maintains a temperature at 235° C. to 245° C. for 15 to 25 minutes, followed by applying a load at a maximum spring displacement for about 1.5 to 2.5 seconds; and the step (d) performs the shot peening process with SWRH82A as a material, by first using shot balls having a diameter of about 0.6 mm for about 40 minutes, and then using shot balls having a diameter of about 0.3 mm for about 20 minutes.