2000 年 2000 巻 45 号 p. 1-7
Spring weight-saving will be achieved by increased design stress. However, in case of the conventional spring steel, high strength steel reduces corrosion fatigue life and toughness, and it gets down the reliability of springs in actual environment. In this paper, we propose newly developed spring material with emphasis on improvement of shot peening to satisfy higher strength and corrosion fatigue life simultaneously.
The chemical elements of developed material were designed under the following philosophies, where Si stays at 1.8% for sag-resistance, C is reduced to 0.4% for the corrosion fatigue life, Ni is added by 0.5% for the controled forming of corrosive pit, and a trace of B and Nb is added for the strength of austenitic grain boundary which be way of corrosion fatigue's crack propagation and fine grain size respectively.
Experimental results by straight test piece and coil spring under high stress shows that the developed spring material is effective for improving corrosive fatigue life and delayed fracture strength. Developed spring material can achieve 20% weight-saving under 1200MPa design stress comparing with the conventional spring steel.