Spring materials are selected according to the required strength, fatigue resistance, operating temperature, corrosion resistance, manufacturing process and service environment. Common materials include carbon and alloy spring steels, stainless steels and non-ferrous alloys such as phosphor bronze, copper alloys and nickel-based alloys.
This page provides engineering reference information for metallic spring materials, with particular emphasis on wire used for helical compression, extension and torsion springs. Material requirements for leaf, disc and other specialised springs should also be checked against the relevant product and material standards.
A wide range of metallic materials can be used for springs. Common material groups include:
Material selection should take account of:
Spring strength cannot normally be specified independently of material size and manufacturing condition. In particular, the tensile strength of cold-drawn spring wire generally varies with wire diameter.
The standards applying to spring wire have changed since the original RoyMech material notes were compiled. The following references are relevant to current UK engineering practice.
| Standard | Application | Status / Note |
|---|---|---|
| BS EN 10270-1:2024 | Steel wire for mechanical springs – patented cold-drawn unalloyed spring steel wire | Current replacement for the earlier editions of BS EN 10270-1. |
| BS EN 10270-2:2011 | Steel wire for mechanical springs – oil-hardened and tempered spring steel wire | Covers unalloyed and alloyed oil-hardened and tempered spring wire. |
| BS EN ISO 6931-1:2020 | Stainless steels for springs – wire | Current stainless spring-wire reference. It replaced the withdrawn BS EN 10270-3:2011 in UK practice. |
| BS ISO 8458-1:2026 | Steel wire for mechanical springs – general requirements | General requirements for round steel spring wire. |
| BS ISO 8458-2:2026 | Steel wire for mechanical springs – patented cold-drawn non-alloy steel wire | International spring-wire specification adopted as a British Standard. |
| BS ISO 8458-3:2026 | Steel wire for mechanical springs – oil-hardened and tempered wire | International spring-wire specification adopted as a British Standard. |
| BS ISO 683-6:2023 | Hot-rolled steels for quenched and tempered springs | Relevant to spring steels supplied as bars and wire rod for subsequent forming and heat treatment. |
| BS EN 12166:2024 | Copper and copper alloys – wire for general purposes | Includes copper-alloy wire intended for spring manufacturing applications. |
The applicable standard should always be checked for the required material grade, diameter range, tensile strength, dimensional tolerance, surface condition and testing requirements.
Patented cold-drawn carbon steel wire is extensively used for mechanical springs. Material grades are selected according to required tensile strength, loading duty, wire diameter and manufacturing requirements.
Historically, EN 10270-1 has used the following familiar grade designations:
| Grade | Traditional Description |
|---|---|
| SL | Low tensile strength, principally static duty |
| SM | Medium tensile strength, principally static duty |
| SH | High tensile strength, principally static duty |
| DM | Medium tensile strength, dynamic duty |
| DH | High tensile strength, dynamic duty |
Exact grade definitions, diameter ranges and mechanical properties should be taken from the current edition of the applicable standard rather than from historical summary values.
Oil-hardened and tempered spring wire is available in unalloyed and alloyed grades and is widely used for highly stressed mechanical springs. Applications include compression and extension springs subjected primarily to torsional stress and some spring components subjected to bending.
Traditional EN 10270-2 grade families include carbon, chromium-vanadium and silicon-chromium spring steels with grades selected according to static, medium-fatigue and high-fatigue duties.
| Material Family | Traditional Grade Examples | Typical Application Class |
|---|---|---|
| Carbon spring steel | FDC, TDC, VDC | Static through higher-fatigue applications |
| Chromium-vanadium spring steel | FDCrV, TDCrV, VDCrV | Higher-performance cyclic spring applications |
| Silicon-chromium spring steel | FDSiCr, TDSiCr, VDSiCr | Highly stressed and fatigue-critical spring applications |
The prefixes and grade designations should be interpreted using the relevant edition of the material standard. Do not select allowable stress solely from the simplified duty descriptions above.
Stainless spring steels are used where corrosion resistance is required in addition to spring properties. Austenitic stainless spring wire is common, although the appropriate grade depends on strength, temperature, corrosion environment, magnetic requirements and manufacturing process.
The old RoyMech page referred to BS EN 10270-3:2001. That standard family is no longer the current UK reference for stainless spring wire. Stainless spring wire is now covered by BS EN ISO 6931-1:2020.
The standard covers stainless steel grades commonly supplied as cold-drawn round wire for springs and spring parts exposed to corrosive conditions and, for suitable grades, moderately elevated temperatures.
High-carbon cold-drawn spring wire is widely used for small and medium-sized springs requiring high tensile strength and good fatigue performance.
It is particularly suited to highly stressed springs operating under normal environmental conditions. Corrosive environments or elevated temperatures may require a different material or suitable protective treatment.
Oil-hardened and tempered wire is a widely used spring material available in carbon and alloy steel grades. It is particularly useful where larger wire sizes, high working stresses or improved fatigue performance are required.
The appropriate grade should be selected according to the loading duty, required strength, operating temperature and applicable wire specification.
Hard-drawn carbon steel wire provides an economical material for general spring applications where the highest fatigue strength and dimensional precision are not required.
Its suitability depends strongly on wire diameter, working stress, loading cycles and environmental conditions.
Chromium-vanadium spring steels are used for springs requiring good strength, toughness and fatigue resistance. They have traditionally been selected for applications involving cyclic loading and, with the appropriate grade and processing, shock loading.
Silicon-chromium spring steels are widely used for highly stressed springs requiring good fatigue performance. Typical applications include demanding cyclic-duty springs where high strength and resistance to relaxation are important.
Stainless spring steels combine useful spring properties with improved corrosion resistance. Austenitic grades are widely used for general corrosion-resistant springs, while other stainless grades may be selected for particular combinations of strength, temperature and environmental requirements.
Corrosion resistance varies substantially between stainless grades and with the service environment; the term "stainless steel" should therefore not be treated as a single material specification.
Spring brass is readily formed and offers useful electrical conductivity and corrosion resistance. Its mechanical strength and fatigue performance are generally lower than those of high-strength spring steels, so it is normally selected where electrical, forming or corrosion properties are important.
Phosphor bronze combines corrosion resistance, electrical conductivity and good resistance to repeated flexure. It is widely used for electrical contacts, clips, small springs and other applications where copper-alloy properties are advantageous.
Beryllium-copper alloys can provide high strength, good fatigue performance, electrical conductivity and corrosion resistance after appropriate heat treatment.
Nickel-based spring alloys are used where combinations of corrosion resistance, elevated-temperature performance or resistance to stress relaxation are required beyond the capabilities of conventional spring steels.
Properties vary considerably between nickel-alloy grades, so design values must be obtained for the specific alloy and material condition.
Titanium alloys offer high specific strength and low density and may be selected where spring mass is particularly important, including aerospace applications.
Their elastic modulus is substantially lower than that of steel, which has a major influence on spring stiffness and geometry. Material grade, manufacturing process, surface condition and fatigue behaviour require careful consideration.
Spring-wire strength depends on material composition, manufacturing process, heat treatment, surface condition and wire diameter. A material name alone is therefore insufficient to define the allowable spring stress.
For several traditional spring-wire materials, ultimate tensile strength has historically been approximated over a limited diameter range using:
where:
| Material | Diameter Range (mm) | Exponent m | A (MPa) |
|---|---|---|---|
| Music wire | 0.1 – 6.5 | 0.145 | 2211 |
| Oil-tempered wire | 0.5 – 12 | 0.187 | 1855 |
| Hard-drawn wire | 0.7 – 12 | 0.190 | 1783 |
| Chromium-vanadium | 0.8 – 12 | 0.168 | 2005 |
| Chromium-silicon | 1.6 – 10 | 0.108 | 1975 |
| 302 stainless | 0.3 – 2.5 | 0.146 | 1867 |
| 302 stainless | 2.5 – 5 | 0.263 | 2065 |
| 302 stainless | 5 – 10 | 0.478 | 2911 |
| Phosphor bronze | 0.1 – 0.6 | 0 | 1000 |
| Phosphor bronze | 0.6 – 2.0 | 0.028 | 913 |
| Phosphor bronze | 2.0 – 7.5 | 0.064 | 932 |
Older preliminary spring-design methods sometimes estimate torsional yield strength from ultimate tensile strength. The original RoyMech notes give the broad empirical range:
The original reference further gives the following approximate relationships:
The shear modulus G, historically called the modulus of rigidity, is required in the calculation of many helical and torsional springs.
The following values are typical engineering reference values. Actual values vary with alloy, material condition and temperature.
| Material | Typical Shear Modulus G (GPa) |
|---|---|
| Carbon steel | 78.6 |
| 316 stainless steel | 68.9 |
| Brass | 34.5 |
| Phosphor bronze | 41.4 |
| Monel-type nickel-copper alloy | 65.5 |
| Inconel-type nickel alloy | 72.4 |
| Beryllium copper | 50.0 |
For accurate spring-rate calculations, use the modulus specified for the actual material grade, condition and operating temperature whenever that information is available.