Precipitation Strengthened Spring Steel for Automotive Suspensions

The addition of a small amount of vanadium and columbium. into SAE 9260 was found to give the steel excellent sag resistance, caused by the precipitation strengthening of V and Cb. The precipitation strengthening enhances the yield strengths in tension and torsion obtained from the specimens with various tempered hardness values after quenching from 900°C (1652°F). The sag resistance was estimated by means of load relaxation under the stresses of 1050 MPa (149 ksi) and 1128 MPa (164 ksi). Using this steel for coil springs is expected to reduce the weight by 25%, and several new models using the coil springs wound from V-Cb treated steels are going to appear in the market.