| 摘要 |
PROBLEM TO BE SOLVED: To provide a coil spring having a shallow nitride layer, whereby it is possible to secure a high anti-settling property even when a high load is applied and which can show a high fatigue strength. SOLUTION: A coil spring concerned is structured so that its depth of nitride layer ranges between 20-50μm, internal hardness is more than HV540, the surface roughness is below Rmax 15μm, and the steepness is below 0.02. Thus the resultant coil spring is equipped with a long lifetime and presents a small fatigue settling, i.e., the settling amount (residual shear strain) with a repetition frequency of 10<7> is no more than 3×10<-4> even with a high load stress according to the test stressτ=70±65kgf/mm<2> .
|
