There is no 0.656" listed in the spec. There is 0.625" (Min tensile is 226 KSI, no YS listed) and for 0.687 (Min tensile 224, No YS listed). It is also mentioned that you can interpolate the values for intermediate diameters.
Well that's not particularly helpful, but thanks for the reply. I've been unable to locate a yield strength for it either, thus my request here. Is this because it is a spring material? It still must have a measurable yield strength, wouldn't it?
If you need to know TYS, buy a sample of the material and have a metallurgical lab run a tensile test. With the .656" diameter, you have enough stock to machine a standard .505" test bar.
The spring material specified by ASTM A401 has a very high yield and tensile strength, and limited elongation. When testing a straight section of the original wire, the yield strength will typically be in the range of 90-98% of the ultimate tensile strength, with elongation < 8%. However, is this really what you need? If you are trying to evaluate the performance/failure of an actual cold-coiled spring (helical compression, torsion, tension, etc.), then there are many processing variables that will affect this, including whether the parts are shot peened, what heat treatments are performed on the springs, etc.
Springs are commonly designed to fatigue limits, not yield. The yield on these materials is so high that it does not make sense to measure it.
After all the yield strength is not a 'real' material property, merely a naming convention.
