Optimising industrial spring life – material selection a critical factor

A small compression spring used in the actuation of an electromechanical switch will be expected to perform faultlessly for 000’s of cycles. The compression spring in an aircraft ejector seat mechanism on the other hand, stored under compression, will be expected to perform once to order.

Key considerations to maximise life

For many standard duties a spring produced from range 3 music wire, or high
tensile stainless steel is perfectly adequate. In operation the material is subject to various degrees of stress and therefore must be highly tensile.

A standard stainless steel will operate in conditions of up to 300°C. However, some grades of stainless steel have restricted environmental operating conditions. The basic “music wire” used for producing springs is however available in different grades.

Stainless steel not always appropriate


Here is a good example of the detailed consideration of the most suitable material that needs to take place: type 302 stainless should not be used in conditions where acids are present making it unsuitable for applications processing citrus fruits where instead type 316 should be used – which is incidentally also suitable for medical applications where contact with blood and tissue may occur or in
low salt conditions.

Medical and electrical applications can require very special materials

Components used in the medical industry are often made from platinum; iridium or gold may also be used. A readily worked alloy, platinum–iridium is much harder, stiffer, and more resistant to chemicals than pure platinum, which is relatively soft. Platinum–iridium is also very resistant to high-temperature electric sparks and is widely used for
electrical contacts.

Special materials for arduous conditions

Extreme operational environments put quite different demands on the component.  In the offshore industry for example, Inconel is usually the material of choice because of the specific properties of Inconel alloys which render them oxidation and corrosion resistant, well suited for service in such environments and which may be subject to pressure and heat. When heated, Inconel forms a thick, stable, oxide layer protecting the surface from further attack.