Spring within the elastic range of use, after unloading should return to its original position, I hope plastic deformation as small as possible, so the wire should have high elastic limit, yield strength and tensile strength. The higher the yield-to-tensile ratio, the closer the elastic limit is to the tensile strength, so the more the utilization of strength is increased, the stronger the resulting spring is.
Spring relies on elastic deformation to absorb impact energy, so the spring wire does not have to have high plasticity, but at least have to bear the plastic forming spring, and enough to withstand the impact of energy toughness.
Spring is usually long-term work under alternating stress, and therefore have a high fatigue limit, as well as good creep and resistance to relaxation performance.
Spring used in specific environment, there are some special requirements on the wire, for example: the use of the spring in the corrosive medium, must have good corrosion resistance. Spring used in precision instruments should have long-term stability and sensitivity, low temperature coefficient, high quality factor, small after-effect, and constant modulus of elasticity. Springs operating at high temperatures require that sufficient elastic limits and good creep resistance be maintained even at high temperatures.
In addition, spring steel wire should also consider the forming process and heat treatment process. Cold-drawn spring steel wire and oil quenched and tempered spring steel wire are supplied directly to the state of the wire around the spring, the spring after the formation of the stress-relieving treatment directly. Cold-drawn spring wire tensile strength slightly higher than oil quenching and tempering wire. Large-scale cold-drawn steel wire elasticity is too large, winding the spring is very difficult, so cold-drawn spring wire specifications generally less than 8.0mm, oil quenching and tempering wire specifications generally less than 13.0mm. In fact, the spring diameter 13.0mm multi-use light pull state spring wire, cold drawn around the system after forming quenching and tempering. Steel wire diameter of more than 15.0mm mostly use heating winding system spring.
Spring according to the operating state can be divided into static spring and dynamic spring. Static spring refers to the limited number of active service spring vibration, such as safety valve spring, spring pad, pan spring, scheduled load spring, mechanical spring, watch springs and so on. Dynamic spring refers to the number of vibration of the service period of more than 1 × 106 times the spring, such as the engine valve spring, vehicle suspension spring, shock spring, coupling spring, elevator buffer spring. Static spring material selection mainly consider the tensile strength and stability, dynamic spring material selection mainly consider the fatigue, relaxation and resonance performance.
According to the spring load conditions can be divided into light load, general load and heavy load three states. Light load refers to the static stress, stress lower, smaller deformation of the spring, such as safety devices with springs, vibration absorption and so on. Design life of 103 to 104 times.