Material considerations

What lies ahead in the realm of spring manufacture? Of course there are constant refinements to designs and the introductions of new ranges. In particular though, it is often the choice of material which gives us most thought for the future as it shows the way forward in spring technology. 

I use the term ‘technology’ here advisedly since it is not just a question of choosing a new material and adapting it to an established process, often it is a case of defining a new way of working and matching materials with the new demands of new applications in some very sophisticated ways that extend present boundaries and make possible new products that work much better than previous designs.

Much of this development comes in response to the needs of design engineers and manufacturers for eco-friendly, lighter and easier to manipulate spring products to suit newly envisaged requirements. Probably the most important consideration for a custom spring design is the choice of material which can greatly influence the size, suitability, performance and longevity of the finished item. Key factors affecting material choice for a particular application include: meeting stress conditions, either static or dynamic; capability of functioning at a required operating temperature; compatibility with surroundings - eg corrosive environment; and special requirements such as conductivity, constant modulus, weight restrictions, magnetic limitations, etc.

The specification of springs can involve production in an extremely wide range of materials such as beryllium copper, brass, hard drawn carbon steel, oil tempered carbon steel, oil tempered chrome silicon, oil tempered chrome vanadium, Elgiloy, Hastelloy, Inconel, Monel, music wire, phosphor bronze, plastic composites, and stainless steel. In recent years significant advances have been made with some innovative spring materials brought to market as standard catalogue products. In particular we see increasing use of so called “super” alloys, especially Elgiloy – a truly exotic mix of many metals, mainly being Cobalt, Chromium, Nickel, Iron, Molybdenum and Manganese. A derivative from the early days of aerospace development when it was used for control cables on the Lockheed SR-71 Blackbird airplane, Elgiloy is a tough, ductile exotic alloy mix known for its excellent resistance to corrosive environments, elevated temperature resistance and high strength. 

Elgiloy exhibits no magnetism and is blue/brown in colour as a result of heat treatment. It offers a good solution for extreme environ-ments accompanied by mechanical properties simi-lar to high carbon spring steel (music wire). The mechanical properties of Elgiloy are often superior to stainless steel and other nickel alloys. It may also be considered for spring components in some medical applications and can often be used in lieu of titanium where it offers several advantages. Elgiloy offers excellent bio-compatible characteristics and can be used from extreme low temperatures up to +450°C.

This amazing mix of characteristics sees Elgiloy being used wherever exceptional performance is required, such as for gas turbine parts, rocket motors, nuclear reactors, submarines and interestingly orthodontic spring forms where varying levels of temper permit its use where light springs are needed with considerable strength and the possibility of manual adjustment to suit changes in the oral alignment provides flexibility and control. 

More industrially, springs made of Elgiloy offer exceptional performance in severe conditions, including extreme high or low temperatures, under great pressure and exposed to outdoor conditions, including extreme weather. Situations where lesser alloys would simply not be adequate to the task.