High Strength Spring

Author:  Koyama et al.
Source:  US Patent 5,258,082
Doc ID:  1993113
Year of Publication:  1993
Abstract:  
A spring steel containing 0.35 to 0.50% of carbon is refined to the hardness of 2.50 to 2.70 mm in Brinell indentation diameter (HBD) by rapid cooling for quenching and tempering. This spring steel is subjected to warm shot peening at a temperature of 150 to 300 degrees C. (423 to 573 K) by using long-lived practical shots with the normal hardness of 2.65 to 2.80 mm in HBD, whereupon a high-stength spring is obtained having a compressive residual stress in its surface and enjoying the maximum shearing stress of 110 to 135 kgf/mm2 (1080 to 1325 MPa).