The selection of spring material shall be determined according to the spring's nature under load, stress state, stress size, working temperature, environmental medium, service life, requirements for electromagnetic conductivity, process performance, material source, price, and other factors.

When determining the sectional shape and size of materials, the series sizes specified in national standards and ministerial standards shall be preferred, and materials with non-standard series specifications shall be avoided as far as possible.

The common materials of springs are mainly divided into metal materials and non-metallic materials.

Medium and small springs, especially spiral tension springs, should give priority to the use of strengthened steel wire, lead bath isothermal cold drawn steel wire, and oil quenched and tempered steel wire, with high strength, good surface quality, fatigue performance higher than ordinary quenched and tempered steel wire, simple processing, good processability, and stable quality. The carbon spring steel wire and the piano steel wire produce large residual stress after cold drawing. The residual stress of the spring after machining is large, the size changes greatly after tempering, and the size accuracy is difficult to control. The strength of oil quenched and tempered steel wire shall be adjusted after being drawn to the specified size. There is no residual stress.

After forming, the spring is tempered at a low temperature with a small size change. The heat stability is better than cold drawing. Reinforcing steel wire. For large and medium-sized springs, for springs with high load accuracy and stress, cold-drawn materials or polished steel after cold drawing shall be selected. For springs with low load accuracy and low stress, hot-rolled steel can be used.

Flat springs are generally made of 55Si2Mn, 60Si2MnA, 55SiNvB, 55SiNmoV, 60CrMn and 60CrMnB.

The material section of the coil spring should preferably be circular. The square and rectangular section materials have the strong bearing capacity and good impact resistance, which can make the spring smaller. However, the material source is few and the price is high. Except for special needs, this material is generally not selected.

In recent years, the development of round steel wire flattening instead of trapezoidal steel wire has achieved good results. Spring materials working at high temperatures need good thermal stability, anti-relaxation or creep, oxidation resistance, and corrosion resistance to some media. With the increase of the working temperature of the spring, the elastic modulus of the spring material decreases, leading to the decrease of the stiffness and the bearing capacity. Therefore, the change rate (value) of the elastic modulus of the spring working at high temperatures must be understood, and the impact of the reduced bearing capacity of the spring on the service performance must be calculated. According to GB1239, when the working temperature of an ordinary spiral spring exceeds 60 ℃, the shear modulus shall be corrected. The formula is Gt=KtG, where G is the elastic modulus at room temperature; Gt is the shear at working temperature, and t is the variable modulus; Kt is the temperature correction factor. The spring materials used at low temperatures shall have good low-temperature toughness, and carbon spring steel wire, piano steel wire, 1Cr18Ni9 austenitic stainless steel spring steel wire, copper alloy, and nickel alloy shall have good low-temperature toughness and strength.

At low temperatures, the brittleness of materials is very sensitive to surface defects, so strict requirements are put forward for the surface quality of materials. As the corrosion degree of environmental medium to materials under low temperature is far lower than that of greenhouse, cadmium, and zinc plating are likely to cause low temperature and embrittlement. At this time, the elastic modulus and expansion coefficient of the material does not change much, which can be ignored in the design. The selection of spring steel spring hardness (i.e. strength) shall be based on the bearing capacity and stress of the spring. However, hardness is closely related to plane strain fracture toughness. With the increase in hardness, the plane strain fracture toughness (KIC) decreased significantly. This means that when determining the hardness value of the spring, the hardness value of the spring should be low on the premise of meeting the requirements of the spring characteristics.

When selecting spring materials, pay attention to the hardenability of steel. Whether the section of the spring material is in the quenching state has a great influence on the quality of the spring. The electric spring using the spring itself as the conductor or the spring working in a humidity-changing environment, such as water (including sea water) and water vapor, usually uses copper and gold materials. Corrosion-resistant materials, such as stainless steel or nickel alloy, are usually used for springs in acidic contact with other corrosive media.

For springs used under general environmental medium conditions, ordinary spring steel shall be used. After the spring is made, its surface shall be coated with an antirust coating or electroplated (galvanized, cadmium plated, copper plated) to prevent corrosion. To ensure that the accuracy of the weighing instrument and the spring used in the instrument is not affected by the temperature change, the constant elastic alloy with little change in elastic modulus and expansion coefficient is generally selected. Reinforced plastics can be used for springs that require lightweight, insulation, anti-collision, anti-corrosion, and other special purposes. At present, the most suitable plastic spring is thermosetting reinforced plastic GFRP with epoxy resin and phenolic resin as the matrix and glass fiber as the reinforcement. The anti-vibration rubber can also be used to manufacture various rubber springs.

Keneng is a leading manufacturer of customized springs, providing various customized springs. For non-standard spring customization, customers only need to coordinate design and production with us, and select the spring material, wire diameter, size, and special processing technology according to the actual use environment, installation space, and pressure. If you have any needs, please contact Keneng, and we will provide you with the best service.