| 摘要 |
PROBLEM TO BE SOLVED: To provide a stainless-steel tap spring for cell, low in contact electric resistance and improved in soldering property because of dispersion and precipitation of Cu rich phase or Cu enrichment on a passive film or the most outer layer. SOLUTION: The base material of this tap spring is composed of the stainless steel wherein the second phase containing Cu as a main constituent of above 1.0 mass % is dispersed in a matrix phase by the ratio of above 0.2 vol.%, and the second phase containing Cu as the main constituent is exposed on the surface of the base material through the passive film. The stainless steel, wherein the second phase containing Cu as the main constituent is not dispersed and precipitated, can be used, but in this case, the ratio of Cu concentration to the concentration of Cr, Si and Mn on the passive film or the most outer layer on the surface of the base material, is controlled to be Cu/(Cr+Si) >=0.1, Cu(Si+Mn)>=0.5. The soldering property is greatly improved when the precipitation and dispersion of the second phase containing Cu as the main constituent, and the Cu enrichment on the passive film or the outermost layer, are combined. |
