2001 年 2001 巻 46 号 p. 41-65
Austenitic stainless steels such as SUS 304 have been widely used for small sized springs depending on improved strength generated by deformation induced martensitic transformation during wire drawing process. It has the advantage of superior characteristics of corrosion resisting, heat resisting and nonmagnetic properties too. However, actual fatigue endurance of austenitic stainless steels is not superior compared with those of other steels with the same strength characters and the endurance test data has a tendency of scattering. It is pointed out in some occasion that the endurance limit of stainless steel wire is superior for the materials with lower martenisitic transformed phase contents despite having low tensile strength. As controversial comment can be also heard in other occasions, the effect of martensitic transformation upon fatigue endurance of austenitic stainless steel wires has not been commonly understood in general. Therefore, the reasonable methods for controlling the quality of small sized stainless steel springs has not been established yet. For this reason, they have been applied in only a limited cases. In this study, some trials for grasping the governing factors to improve fatigue endurance and the statistical fatigue characteristics of austenitic stainless steel have been conducted. Research Committee on Endurance of Stainless Steel Wires was established in July 1995 to investigate the governing factors in the fatigue endurance of austenitic stainless steel wire form the viewpoints of tensile strength, surface roughness, hardness of surface layer and deformation induced martensitic transformation. A lot of experimental data have been accumulated in this committee until October 1999. As a result, valuable experimental data and some tips for the manufacturing process of wire and spring were obtained as presented in this paper.