The choice of spring material should be determined according to factors such as the nature of the spring’s load, the state of stress, the magnitude of the stress, the working temperature, the environmental medium, the service life, the requirements for conductive and magnetic properties, the process performance, the source of the material, and the price of the spring.
When determining the cross-sectional shape and size of the material, the series of dimensions stipulated by the international standards should be selected first, and materials with non-standard series specifications should be avoided as far as possible.
Medium and small springs, especially spiral tension springs, should be given priority to steel wires that have been strengthened, lead bath isothermal cold drawn steel wires and oil-quenched tempered steel wires.
How to choose the spring material correctly?
The carbon spring steel wire and piano wire produce a large residual stress after cold drawing. After the spring is processed, there is a large residual stress. After tempering, the size changes greatly, and it is difficult to control the dimensional accuracy. Oil-quenched and tempered steel wire is modulated and strengthened after the steel wire is drawn to the specified size. There is basically no residual stress. After the formed spring is tempered at low temperature, the size change is small, and the heat resistance stability is better than that of the cold-drawn reinforced steel wire.
Large and medium-sized springs, cold-drawn or cold-drawn polished steel should be used for high load accuracy and stress. For springs with lower load accuracy and stress, hot-rolled steel can be used.
The material cross-section of the coil spring should be a circular cross-section first. Square and rectangular cross-section materials have strong bearing capacity, good impact resistance, and can reduce the size of the spring. However, the material sources are few and the price is high. Except for special needs, generally try not to choose this material. In recent years, the development of flattened round steel wire instead of trapezoidal steel wire has achieved good results.
The spring material that works at high temperature requires good thermal stability, resistance to relaxation or creep, resistance to oxidation, and resistance to certain medium corrosion.
The spring material used at low temperature should have good low temperature toughness. Austenitic stainless steel spring steel wire such as carbon spring steel wire and piano wire, copper alloy and nickel alloy have good low-temperature toughness and strength.
At low temperatures, the brittleness of the material is very sensitive to surface defects. Therefore, the surface quality of the material should be strictly required.
At low temperatures, the environmental media will corrode the material much less than in the greenhouse, and cadmium and zinc plating can easily cause cold embrittlement.
At low temperatures, the elastic modulus and expansion coefficient of the material does not change much, so it can be ignored in the design.