Spring design formula and calculations

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Vickers 維氏硬度 HVBrinell 勃氏硬度壓痕HBRockwell 洛氏硬度(鋼)HRCShore 蕭氏硬度HS
Type of wire     
CodeNameCharacteristicsG(kgf/mm2)Specific gravity (g/cm3)Feature Description
SWRMLow carbon steel wire SAE1008Widely used80007.85The strength is low, but the toughness is good, the weldability is good, and the cold stamping property is excellent. It is often used to manufacture products such as chains, rivets, bolts, and shafts.
SW-ASWCWidely used80007.85Hard steel wires are classified and named according to their carbon content, diameter, mechanical properties and use. JIS G 3521 divided into three types: SW-A, SW-B and SW-C. According to the carbon content of the wire, the hardness is determined. The minimum carbon content is 40C and the maximum is 80C.
SW-BHard steel wire Type BWidely used80007.85
SW-CHard steel wire Type CWidely used80007.85
SWPAPiano wire Type AWidely used, Corrosion resistant80007.85General use, high durability, piano steel wire can be used for engine valve springs, mechanical springs and musical instruments.
SWOAOil tempering line Type AWidely used80007.85Oil tempered carbon steel wire for spring SWO (JIS G 3560), Oil tempered carbon steel wire for general valve SWO-V (JIS G 3561), Oil tempered chrome vanadium steel wire for fatigue resistance valve SWOCV-V (JIS G 3565 ) Heat and fatigue resistance 41-55 Spring material that is more durable than piano steel wire. Commonly used in car shock absorbers, engine valve springs.
SUSWPAStainless steel wire No.1Widely used, Heat resistant, Corrosion resistant70008.02304 is a general-purpose stainless steel that is widely used to make equipment and parts that require good overall properties (corrosion resistance and formability). 301 stainless steel exhibits obvious work hardening phenomenon during deformation, and is used in various occasions requiring higher strength. 302 stainless steel is essentially a variant of 304 stainless steel with higher carbon content, which can obtain higher strength by cold rolling. 316 stainless steel contains aluminum, so its resistance to pitting corrosion in marine and chemical industry environments is much better than 304 stainless steel.
BeCuWBeryllium copper wireConductive, Non-magnetic, Corrosion resistant45008.6Also known as copper beryllium, beryllium bronze or spring copper, it refers to a copper alloy with a beryllium content of 0.5 to 3%, sometimes adding other alloying elements. Beryllium copper is a non-magnetic, non-sparking high-strength material with excellent metal processing. It has many applications in harmful environments, musical instruments, precision measuring devices, ammunition and aerospace.
PBWPhosphor‑bronze wireConductive, Non-magnetic, Corrosion resistant43008.8Phosphor bronze wire is a high strength copper alloy with excellent corrosion resistance, fatigue strength, mechanical properties and electrical conductivity. Uses Springs, guitar strings, high-performance electrical terminals, electronic latches, electroplating hooks, mechanical and hardware parts.
BsWBrass wireConductive, Non-magnetic, Corrosion resistant40008.5
Austenitic Stainless Steel     
The most commonly seen 304 stainless steel is this type of stainless steel. Its standard composition is 18% chromium and 8% nickel, which is generally called 18-8 stainless steel. The characteristics of this type of stainless steel are non-magnetic, its metallographic structure cannot be changed by heat treatment, and its workability is good. Because it contains an alloying element-nickel, its corrosion resistance is better than that of chromium-only (nickel-free). The other two types of stainless steel.
The main uses of 300 series stainless steel are: general civilian use such as kitchen tableware, building materials, medical and health equipment, food processing materials, transportation, chemical equipment and pipe fittings, mechanical equipment and parts. For ordinary people, the so-called stainless steel refers to 300 series stainless steel (especially 304 stainless steel).
NameHardness NumberCharacteristic
Hardness (HV)Tensile strength (N/mm2)Yield strength (N/mm2)Elongation (%)
SUS 3011/2H310~370≧ 930≧ 510≧ 10
3/4H370~430≧ 1130≧ 745≧ 5
H430~490≧ 1320≧ 1030
EH490~530≧ 1570≧ 1275
SEH≧ 530≧ 1740≧ 1450
SUS 304O≦ 200≧ 520≧ 205≧ 40
1/2H250~310≧ 780≧ 470≧ 6
3/4H310~370≧ 930≧ 665≧ 3
H≧ 370≧ 1130≧ 880
SUS 305O≦ 200≧ 480≧ 175≧ 40
SUS 310SO≦ 200≧ 520≧ 205≧ 40
SUS 316LO≦ 200≧ 480≧ 175≧ 40
Martensitic Stainless Steel
The chemical composition of this type of stainless steel contains 13% chromium, less than 0.15% carbon and a small amount of other element alloys. The raw material is cheap, magnetic, hardened by heat treatment, and increased in strength. However, because it does not contain nickel, its corrosion resistance is inferior to that of ordinary 304 stainless steel, so it can only be used in mildly corrosive environments. General uses include bearings, medical appliances and tools.
NameHardness NumberCharacteristic
Hardness (HV)Tensile strength (N/mm2)Yield strength (N/mm2)Elongation (%)
SUS 420J2O≦ 247≧ 540≧ 225≧ 18
SUS 440AO≦ 200≧ 450≧ 205≧ 22
Ferritic Stainless Steel
The representative grade of this type of stainless steel is 430, its standard chemical composition is 16~18% chromium, and its carbon content is low. This type of stainless steel is magnetic, and if the stainless steel sheet we see can be attracted by a magnet, it is likely to belong to this type of stainless steel. It is less expensive because it does not contain nickel. Typical uses are kitchen utensils, netting and accessories.
NameHardness NumberCharacteristic
Hardness (HV)Tensile strength (N/mm2)Yield strength (N/mm2)Elongation (%)
SUS 410LO≦ 200≧ 360≧ 195≧ 22
SUS 430O≦ 269≧ 590≧ 245≧ 15
Precipitation Hardening Stainless Steel
The American Iron and Steel Institute AISI number is 600 series stainless steel. In addition to chromium and nickel, this type of stainless steel also contains precipitation hardening elements such as copper, aluminum and titanium, which harden the material and increase its strength. Typical uses of this type of stainless steel are: valves, motor shafts, petrochemical equipment and golf heads.
NameHeat Treatment NumberCharacteristic
Hardness (HV)Tensile strength (N/mm2)Yield strength (N/mm2)Elongation (%)
SUS 630SAbout ≦375
H900About ≦396≧ 1310≧ 1175≧ 5
H1025About ≦349≧ 1070≧ 1000≧ 5
H1075About ≦319≧ 1000≧ 860≧ 5
H1150About ≦292≧ 930≧ 725≧ 8
HalogenateA phosphate film is attached to the metal surface to enhance the adsorption of oil, which can make the anti-rust ability and electrical insulation better.
RustproofingRustproofing can make the combination of spring and zinc better. Better rust resistance than Electrogalvanizating.
Nickel ElectroplatingElectroplated nickel can prevent rust and be beautiful. Commonly used on battery springs.
Tin ElectroplatingTin plating is a coating with good solderability and certain corrosion resistance.
ElectrogalvanizationEffective anti-rust ability after electroplating. It is not easy to be corroded in acid and alkali. Ductile after electroplating. Can also be bent. Can be electroplated in various colors
Chromium EectroplatingUsually to increase surface hardness and friction resistance. Because chrome is not easy to change color, it is necessary to use the spring in the appearance part. Rust resistance is not as good as galvanized. Expensive.
Gold ElectroplatingIn order to have good electrical conductivity.Expensive.
E-CoatingIt can make the appearance similar to baking paint, the color is uniform and the rust resistance is good, and it is suitable for use on products that require appearance.
Surface PassivationApplied to stainless steel wire, the stainless steel surface is attached with a film to increase corrosion resistance and rust resistance.
Powder CoatingVarious colors can be adjusted,
The surface of the spring can be painted with a layer of 50-300μm.
Shot PeeningSpray spring products with small beads to eliminate stress and increase the service life of springs, often used on compression springs.
GrindUse a grinder to grind the plane at both ends of the compression spring, and the spring can be evenly stressed without tilting when the spring is stressed.
Black OxideBlack with oil on the surface. Can prevent rust. But the effect is limited. To achieve the best results, it is recommended to add anti-rust oil to achieve the best results. Cheap.

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