This post is the first in our series of blogs about what affects spring longevity.

The first question is ‘could a spring last forever?’ and the answer is yes, it could do if

• The operating stresses are not too high
• The working temperature does not cause the spring to lose too much load
• The environment does not cause corrosion
• The spring is not abused
• The spring is well-made and free from imperfections.

If a spring meets the above requirements, yes it could potentially last forever!

Selecting the best material to ensure spring longevity

The wire material used in spring manufacture directly impacts the spring’s lifespan and performance. These properties are severely compromised in an unsuitable spring material, and the spring may not be fit for the purpose. All solid materials have certain properties which lend themselves to the make-up of a spring. Even wood demonstrates elastic potential in its use for making bows for firing arrows! These are considered one of the first representations of spring technology. We will now look at the main materials from which most springs are manufactured today.

Carbon Steel

Carbon steel is the favoured and most common material in spring production. This is because it is relatively inexpensive and widely available. It has high strength and its popularity stems from its high load capacity and consistent performance in high-pressure applications. Disadvantages of this material include its susceptibility to load less at high temperatures and the risk of corrosion.

For spring manufacturers, carbon steel is denoted by the standard EN10270-1 and there are various grades from SL (Static Low) up to DH (Dynamic High). Higher tensile strength and better surface quality results in a greater fatigue life within a dynamic spring application. Spring fatigue life is the ability to withstand thousands, or even millions, of cycles without the risk of fracture.

Stainless Steel

Stainless steel is also a popular choice of spring material, due to its:

• Ability to operate in temperatures up to 300 degrees Celsius
• Resistance to corrosion
• Durability, high yield strength and subsequent ability to withstand intense stress, while still maintaining its form.

On the other hand, it is slightly weaker than materials such as carbon spring steel and more expensive. However, new stainless steels are in development to increase strength while retaining resistance to relaxation under high temperatures.

Silicon Chrome

Silicon Chrome is suitable for springs supporting a great amount of force/shock loads and high-stress applications. This is due to its high tensile strength – particularly at wire diameters exceeding 2mm. It is also able to perform in relatively high-temperature environments, therefore making it a suitable spring material for engine valve springs, firearm recoil springs and automotive suspension.

Exotic Materials

Examples of exotic materials include Inconel®, Elgiloy® and Nimonic®. Exotic materials contain greater concentrations of elements such as nickel, chromium, cobalt and molybdenum and these provide high strength, corrosion resistance (in environments in which stainless steel is at risk of corrosion), oxidation and high temperatures. Consequently, these properties make them ideal materials to use in particularly aggressive environments – high temperatures and levels of corrosion are typically the two main aspects. One example would be their use in the oil and gas industry.

Summary of How Material Affects Spring Longevity

The first questions to ask are, “Would carbon steel work? If not, why not?”. This will usually indicate which material would be suitable. The calculation of operating stresses will determine whether carbon steel has sufficient strength. You must consider how temperature affects spring performance, as temperature causes spring relaxation over time.

Following this, you should consider the environment i.e. is it corrosive? If so, the spring material will need to be resistant to corrosion or coated with corrosion protection.

Opting for materials of a higher grade within a specification results in better quality springs with increased longevity – quality can be looked at in terms of the tensile strength of the material and the surface quality i.e. the fewer flaws in the surface, the better the quality of the material.

Ultimately, it entirely depends on each spring’s unique application.

The flowchart below poses questions about the environments and applications in which a spring may operate. If you follow the appropriate arrows, each answer will suggest a suitable material for the purpose. However, this should purely be a guide. There are several additional caveats to consider, including spring prestressing and the potential need to redesign those with high operating stresses.

For more information about spring longevity or our work producing compression springs, tension springs and torsion springs, visit our other webpages. Alternatively, send an enquiry through our Contact Us page to find out how we can provide you with lean spring solutions. We’re always happy to help with any queries you may have about springs and their applications.

Other blog from this series:
How Fit and Function Affect Spring Longevity