Most solid materials have the ability to flex when a force is applied and return to their shape, although for some materials the amount of flex before breakage may be very small. Some materials may not be regarded as a spring material at all. One good example is paper; when formed into an “origami”-type frog, it will display the characteristics of a spring where flexed and jump when released.
Most mechanical springs are designed with the ability to store energy and release it when required. The amount of energy that can be stored is dependent on the size of the spring and the material from which it’s manufactured.
Springs, wireforms and flat pressings can be manufactured from a wide range of materials, including the following:
High Carbon Steels
High carbon steels are the most common materials in spring manufacturing. Hard-drawn wires for low-stress applications are lower cost, whereas higher tensile materials are more suitable for higher stressed applications and are more expensive. Carbon steels may need additional corrosive protection such as a pre-galvanised coating.
This material contains, approximately, 0.60% to 1.25% carbon content, which gives it strength, hardness, resistance to wear and good shape memory. Adding carbon to steels improves their performance in a variety of application, which makes it suitable for springs in many industries and sectors.
High carbon steels have the highest hardness and toughness of all carbon steels, as well as the lowest ductility – this means that they are more brittle than alloys with less carbon content. Carbon steel can be made from new steel, recycled steel or a combination of the two – at Airedale Springs, we use metal that is 100% recyclable for all of our springs, wireforms and pressings.
Stainless steel is the most popular alloy for springs. They have a high degree of resistance to heat and to corrosion, which means they’re useful for applications where this is a concern; specific grades of stainless steel are available for elevated resistance requirements. Spring wire created from this material is manufactured by cold drawing and, in a spring temper condition, it will be slightly magnetic.
Stainless steel springs, which are stress relieved after forming, may be a light brown colour, requiring an extra cleaning operation if a shiny finish is required.
There are five stainless-steel families:
- Austenitic (properties include being non-magnetic when annealed, ductile, easy to weld, high resistance to corrosion)
- Ferritic (alloys in this group are magnetic, cannot be hardened by heat treatments and don’t have great weldability)
- Duplex (have great resistance to corrosion, good weldability and high tensile strength)
- Martensitic (can be heat-treated, are magnetic, have poor weldability and cannot be cold-formed)
- Precipitation hardening (magnetic, high-strength alloys with moderate resistance to corrosion)
In general, stainless-steel alloys provide many advantages to spring manufacturing and, while each family or grade has its own properties, the alloys tend to have, in general:
- High resistance to corrosion
- High strength and hardness
- High resistance to heat and low temperatures
- High ductility (certain types of stainless-steel alloys, such as austenitic, to have a high degree of ductility)
Stainless steel is also easy to clean and maintain and highly recyclable. Certain grades even provide high hot strength, meaning they’re capable of retaining strength even at high temperatures; this is more common for grades that contain high levels of chromium, silicon or nitrogen, for example.
Chrome Vanadium and Chrome Silicone alloy steels are cold draw steels suitable for shock loads, such as engine valve springs.
Chrome Vanadium – This alloy contains a high amount of chromium, usually between 0.8% and 1.1%, while its vanadium content tends to be 0.18%. Other materials include manganese and silicon. When the percentages change, the properties of the alloy may also change. Chrome vanadium is strong and resistant to wear, and also has high tensile strength. The alloy has different grades, some of which are better suited for springs than others.
Chrome Silicon – Chrome Silicon has a high level of tensile strength (meaning it can withstand shock loads) as well as of resistance to heat. The alloy is durable and resistant to wear and tear, even after repeated uses, and is suitable for applications where high stress and high temperatures are a concern.
Cold-drawn copper alloys are excellent for application where good electrical conductivity is required. Some alloys can also be used for elevated temperature applications or high corrosion resistance is required.
These alloys refer to materials that are not iron-based (if they contain iron, it’s in negligible amounts) and tend to provide a high level of strength and great resistance to wear and corrosion. They are, usually, more expensive than ferrous alloys due to their properties, which will vary depending on the alloyed materials.
For example, non-ferrous alloys can have low weight (if they contain aluminium) or high conductivity (if they have copper, which is ideal for electrical springs and wireforms). Nickel is another popular metal in non-ferrous alloys, and is known for its toughness and ability to perform well in both high and low temperatures.
High Temperature Alloys
Cold drawn Nickel and Chromium alloys are excellent materials for applications that require good corrosion resistance at elevated temperatures.
Nickel Alloys – Nickel is a versatile component that works well with many other metals, so it’s common to find nickel-iron, nickel-copper and nickel-chromium alloys in a variety of sectors. Often used in high-temperature environments, these alloys are also resistant to oxidation and corrosion and are strong across a range of temperatures.
Chromium Alloys – Chromium is a lightweight metal with a high level of resistance to corrosion, so it’s often used as a protective coating for many metals. In its alloyed form, chromium is a great choice of material for springs, since it offers wear and tear resistance and strength at high temperatures.
As spring manufacturers, we produce springs made from all of these materials. For more information on any of them – including which may be the best choice for your spring application – contact us today and our friendly staff will be more than happy to help.
We will also work with you when it comes to developing your spring design, so you can be sure our products meet your exact requirements and the strict demands on your industry, and we offer a spring assembly service as well.