Overview of spring material selection
The choice of spring material should be determined according to factors such as the nature of the spring’s load, working temperature, stress state, service life, requirements for electrical conductivity, process performance, stress, environmental media, material sources, and price.
Second, several important points for attention when selecting spring materials
1. Material factors
Leaf springs generally use flat steels of 55SiMnVB, 55SiMnMoV, 55Si2Mn, 60Si2MnA, 60CrMnB, 60CrMn, etc.
Medium and small springs, especially helical tension springs, should be given priority to using strengthened steel wire, lead bath isothermal cold drawn steel wire and oil quenched tempered steel wire. Its strength and surface quality are higher, and its fatigue performance is higher than that of ordinary quenched tempered steel wire. Fire steel wire, good manufacturability, simple processing and stable quality. For large and medium-sized springs, cold-drawn or cold-drawn polished steel should be used for higher load accuracy and stress; hot-rolled steel should be used for lower load accuracy and stress.
Electrical springs that use the spring itself as a conductor or springs that work under variable humidity conditions, such as water (including sea water) and steam, generally use copper and gold steel.
Springs that work under acid contact with other corrosive media generally use corrosion-resistant materials such as stainless acid-resistant steel or nickel alloy. For springs used under general environmental conditions, ordinary spring steel is selected, and the surface of the spring is made of anti-rust coating or electroplating (zinc plating, cadmium plating, copper plating) to prevent corrosion.
Springs used in weighing instruments and instruments, in order to ensure that their accuracy is not affected by temperature changes, generally use constant elastic alloys with minimal changes in elastic modulus and expansion coefficient.
Reinforced plastics can be selected for special purpose springs that require light weight, insulation, anti-collision, anti-corrosion, etc. Various types of rubber springs can also be made of anti-vibration rubber.
2. Characteristic factors
Strength and hardness have a great relationship with plane strain fracture toughness. Therefore, its selection should be based on the spring bearing properties and stress.
Hardenability, whether or not the cross-section of the spring material is hardened and the degree of hardening, have a great influence on the quality of the spring.
Special type, the material cross-section of the coil spring, the circular cross-section should be preferred. Although square and rectangular cross-section materials have strong bearing capacity and good impact resistance, they have fewer sources and higher prices. Except for special needs, generally try not to choose this material.
3. Temperature factor
Spring materials that work at high temperatures require 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. Carbon spring steel wire, piano steel wire and austenitic stainless steel spring steel wire such as 1Cr18Ni9, copper alloy and nickel alloy have good low temperature toughness and strength. Because under low temperature conditions, the brittleness of the material is very sensitive to surface defects. The degree of corrosion of environmental media to materials is much smaller than that in the greenhouse, and cadmium and zinc plating easily cause cold brittleness. The elastic modulus and expansion coefficient of the material do not change much, so it can be ignored in the design.