Springs n’ Things
One of the common misconceptions we hear about springs is that high-strength steel is used to make springs because it’s “stiffer” than low-strength steel. Now, while it’s true that springs are indeed made of high-strength steel (as well as other materials, of course), the “stiffness” of a spring doesn’t depend on the strength of the material. That is, the “stiffness” of a spring depends on just two factors, namely, the geometry of the spring (i.e., its shape–cross section, length, diameter, thickness, etc.), and a property of the material known as its modulus of elasticity….and the modulus of elasticity is essentially the same for all types of carbon and low alloy steels.
So if high-strength steel isn’t any “stiffer” than low-strength steel, why are springs made of high-strength steel? Because the amount of deflection that a spring can undergo without permanent deformation is indeed a function of the strength of the material. That is, for a given spring geometry, the higher the strength of the material, the greater the deflection that the spring can accommodate before it yields. So even though high-strength steel isn’t any “stiffer” than low-strength steel, a spring that’s made of high-strength steel can carry a greater load than one of the same geometry that’s made of low-strength steel.