2006 年 2006 巻 51 号 p. 1-7
0.4%C-Ti-V steel can enhance the suspension spring design stress comparing the common steel grades such as SAE 9260 or 9254 and has been increasingly applied to automobiles. Titanium and vanadium addition to this steel grade have the two significant features for improving spring corrosion fatigue property. Titanium and vanadium system precipitations lead to the fine austenite grain size with their pinning action. Furthermore tianium and vanadium system precipitations can trap the diffusible hydrogen in the steel during corrosion fatigue. Hydrogen trapping effect and austenite grain size refining can contribute to delay the fatigue crack propagation under the corrosion pit. It is cleared that titanimum has the larger effect than vanadium on the corrosion fatigue property, hydrogen embrittlement, and fracture toughness from this study and there is room for optimizing titanium and vanadium contents.