A spring utilizes the elasticity of its material to convert potential energy into kinetic energy, thereby exerting its function. In theory, materials with higher elasticity are generally better. However, in practical use, the material needs to be selected according to the physical and mechanical properties of the material.
Factors considered in the selection of general materials:
1.Elastic limit
The elastic limit is the stress relative to the maximum force that causes deformation when a force is applied to a material, and the elimination of this force results in no residual deformation. This value is difficult to determine, but relatively speaking, the higher the tensile strength of the material, the higher its elastic limit. At the same time, the elastic limit can be changed through heat treatment processing.
2.Elastic coefficient
The stress that produces a unit strain when a force is applied to a spring material is called the elastic coefficient, also known as stiffness in the industry. This value is the matrix of spring design, and the elastic coefficient of spring material mainly depends on the chemical composition of the material, which may vary slightly due to heat treatment processing.
3.Fatigue strength
The fatigue strength is related to the material selection and the tensile strength of the same material, but there are significant differences due to differences in surface condition, decarburization, heat treatment processing technology, surface strengthening technology, etc.
4.Quenchability
In order to improve the quenching effect, large springs require materials with good quenching properties, which depend on the chemical composition of the material. The critical diameter for oil quenching of chromium vanadium steel is 40mm, and the critical diameter for water quenching is 50mm; The critical diameter for oil quenching of silicon chromium steel is 50mm, and the critical diameter for water quenching is 60-70mm.
5.Heat resistance
Some springs are used in high-temperature environments, and the various mechanical properties of spring materials usually decrease with increasing temperature. Generally, the maximum operating temperature of carbon steel springs is 200 ℃, the maximum operating temperature of general alloy steel is 250 ℃, and the maximum operating temperature of special high-temperature resistant materials can reach 600-900 ℃, such as Inconel-X750, Inconel-X718, etc.
6.Corrosion resistance
Some spring materials may experience corrosion fatigue when used in corrosive environments, and their corrosion resistance depends on the chemical composition of the material and may also vary slightly due to differences in production processes.
7.Electrical conductivity
Electrical appliances and communication equipment are often used for electrical conduction, and copper alloy metals such as brass, phosphor copper, beryllium copper, etc. can be used as spring substrates.
8.Expansion coefficient
Special precision equipment, such as clock spring and precision instrument spring, should avoid the expansion and contraction caused by temperature changes, and special substrates are needed at this time.
Common wire selection for springs:
1.Piano Wire
It uses piano steel wire for toughening treatment, special processing and drawing technology to endow the wire with good dimensional accuracy, good surface condition, and good mechanical properties. Qin steel wire is generally divided into SWP-A; SWP-B； Suitable for applications with high strength, heavy load, and high fatigue life requirements.
2.Carbon Steel Wire
Carbon steel wire is a commonly used spring wire. After toughening treatment, it is processed by drawing and manufactured. Its cost-effectiveness is high, suitable for ordinary application environments, and suitable for springs without impact loads. Common carbon steel wires include 65Mn, 72B, 82A, etc.
3.Stainless steel wire
Stainless steel has both soft and hard wires. Hard wires are used on springs, which are made by tempering, pickling, and cold drawing stainless steel wires. They have excellent corrosion resistance and are also suitable for working conditions that require heat and corrosion resistance. Some grades of stainless steel increase their carbon content to enhance tensile strength, but excessive carbon content may cause stress corrosion and be prone to magnetism. Common stainless steel grades include SUS304, SUS316, SUS202, SUS303, SUS410, SUS420, SUS430, etc.
4.Alloy Steel
There are various types of alloy steel, with common grades including 60Si2MnA, 55CrSi, SEA9254, SWOSC-V, OTEV series, etc. The characteristics of alloy steel materials of different grades are completely the same, resulting in different optimal usage environments for non steel materials. In this case, engineers need to choose suitable spring substrates based on the operating conditions, the frequency of spring reciprocating per minute, and the different stresses.
