Why is 51CrV4 steel suitable for springs?

51CrV4 is a more advanced spring steel, which is used as a high-load important spring with a large cross-section and a valve spring, piston spring, and safety valve spring with a working temperature <300 °C.

For springs, the greater the yield ratio of steel, the better its reliability, for the following reasons:
Because the deformation of 51CrV4 steel is linear when the force does not exceed the yield point, that is, it will return to its original shape after unloading; if the force exceeds the yield point, 51CrV4 steel will produce plastic deformation. Under the same load increment, the deformation of 51CrV4 steel that has passed the yield point is larger than that of the 51CrV4 steel that has not passed the yield point.

So for mechanical components, of course, 51CrV4 steel with small deformation is better, then the yield of 51CrV4 steel should be close to the ultimate breaking strength of steel, that is to say, 51CrV4 steel with large yield ratio is used for spring reliability high.