The spring should return to its original position after unloading. The smaller the plastic deformation, the better. Therefore, the steel wire should have high elastic limit, yield strength and tensile strength. The higher the yield ratio is, the closer the elastic limit is to the tensile strength, so the higher the strength utilization ratio is, the stronger the spring elasticity is.
The spring absorbs the impact energy by elastic deformation, so the spring steel wire does not have to have high plasticity, but at least it must have the plasticity that can bear the spring forming and enough toughness to bear the impact energy.
Spring usually works under alternating stress for a long time, so it should have high fatigue limit and good creep and relaxation resistance.
Spring used in specific environment, there will be some special requirements for steel wire, for example: the spring used in corrosive medium must have good corrosion resistance.
The instrument should have high sensitivity, low sensitivity and long-term stability. The spring working at high temperature is required to keep enough elastic limit and good creep resistance at high temperature.
In addition, the forming process and heat treatment process of spring steel wire should also be considered. Both cold drawn spring steel wire and oil quenched and tempered spring steel wire are directly wound with steel wire in supply state, and the spring is directly used after stress relief treatment after forming. The tensile strength of cold drawn spring steel wire is slightly higher than that of oil quenched and tempered steel wire.
The elasticity of large size cold drawn steel wire is too large, and it is difficult to wind spring. Therefore, the specification of cold drawn spring steel wire is generally less than 8.0 mm, and that of oil quenched and tempered steel wire is generally less than 13.0 mm. In fact, spring steel wire in light drawing state is mostly used for spring with diameter of 13.0 mm, which is cold drawn, wound and then quenched and tempered. Most of the steel wires with diameter above 15.0 mm are made by heating winding process.