spring steel wire needs a high yield point and yield ratio (σs / σb), high elastic limit, high anti-fatigue properties; so that the spring can have the sufficient elastic deformation ability and can load relatively big stress. Because the spring's function is buffering, vibration attenuation and store energy. What's more, the spring steel wire needs definite plasticity and toughness, definite hardenability. Some special spring requires the spring steel wire must have heat resistance, corrosion resistance and stable elastic in a long time.
The spring steel wire can make by many steels, such as the medium carbon steel and high-carbon steel. But their hardenability and strength are lower, can only be used to make the spring with small cross section and small load capacity. In recent years, a new kind of spring steel wire appeared, that is alloy spring steel wire. The alloy spring steel wire with its own advantages can be used to make the important spring with large cross section and high yield limit.
Alloy spring steel wire contain medium and high carbon, general accounts for about 0.5%~0.7%, in order to meet the performance requirements of high elastic and high strength. The elements add in mainly is Si\ Mn\Cr, the main purpose is to improve the hardenability and tempering resistance. But the Si is too much, the steel wire's surface will decarburized easily; the Mn is too much, the grain will grow; the small amount of V and Mo can refine the grain, and improve the strength and toughness. So it is necessary to control the elements volume.