How to choose spring material

The selection of spring material should be determined according to the load nature, stress state, stress size, working temperature, environmental medium, service life, requirements for conductive and magnetic conductivity, process performance, material source and price

In determining the cross-section shape and size of materials, the series sizes specified in national standards and ministerial standards should be preferred, and materials with non-standard series specifications should be avoided as far as possible. For medium and small springs, especially spiral tension springs, steel wires with strengthened treatment, isothermal cold drawn steel wire in lead bath and oil quenched tempered steel wire should be preferred, which have high strength and good surface quality, After cold drawing, carbon spring steel wire and Piano steel wire produce large residual stress. After processing spring, there is larger residual stress. After tempering, the size changes greatly, so it is difficult to control the size accuracy. Oil quenching and tempering steel wire is modulated and strengthened after steel wire is drawn to the specified size, There is basically no residual stress. After low temperature tempering, the size of the formed spring changes little, and the heat resistance stability is better than that of the cold drawn reinforced steel wire

For large and medium-sized springs, cold drawn material or polished steel after cold drawing shall be selected. For springs with low load accuracy and stress, hot-rolled steel can be selected. Flat steel of 55si2mn, 60Si2MnA, 55SiMnVB, 55simnmov, 60crmn, 60crmnb and other flat steels shall be selected for leaf spring, The materials with circular section, square section and rectangular section should be preferentially selected. They have strong bearing capacity, good impact resistance, and can make the spring miniaturized. However, the material sources are few and the price is high. Except for special needs, this kind of material is not selected as far as possible. In recent years, the development of using round steel wire to flatten instead of trapezoidal steel wire has achieved good results

The spring material working at high temperature requires good thermal stability, relaxation or creep resistance, oxidation resistance and corrosion resistance. With the increase of working temperature, the elastic modulus of spring material decreases, resulting in the decrease of stiffness and bearing capacity. Therefore, the change rate (value) of elastic modulus must be known for the spring working at high temperature, According to the provisions of GB 1239, when the working temperature of ordinary spiral spring exceeds 60 ℃, the shear modulus should be modified. The formula is: GT = KTG, in which G is the elastic modulus at normal temperature; GT is the shear modulus under working temperature T; KT — the temperature correction coefficient is selected according to table 2-98

The spring materials used at low temperature should have good low temperature toughness. Carbon spring steel wire, piano steel wire and 1Cr18Ni9 austenitic stainless steel spring steel wire, copper alloy and nickel alloy have good low temperature toughness and strength

At low temperature, the brittleness of materials is very sensitive to surface defects
At low temperature, the corrosion degree of environmental medium is much less than that in greenhouse
At low temperature, the elastic modulus and expansion coefficient of the material change little, so they can not be considered in the design