Springs can be made from many types of material, and RSM is there to help determine what is best for your application. The material selected depends upon many different factors, but the main considerations are: atmospheric conditions of installation, the imposed stress levels, the fatigue life required, or the relaxation properties desired. The main consideration, however is always cost, and an effective balance between mechanical properties and unit cost must always be achieved.
Plain Carbon Steels – generally known as Spring Steel. It is cheap, commonly available, and is readily available in differing grades and most common diameters and gauges. It has very good spring qualities, but like most High Carbon Steels it readily corrodes, and a whole number of protective finishes are now available. Carbon Steels have a restricted range of operation of up to 100 degrees centigrade without excessive relaxation, but beyond this temperature long term relaxation may become an issue. Due care must be undertaken when specifying corrosion preventing finishes, and care must be taken to ensure that hydrogen embrittlement is not introduced, which has resulted in an increasing number of organic coatings reaching the market. If in doubt, we are here as a Company to help specify a suitable protective coating to suit your needs.
Some grades of plain Carbon Steels are available pre-coated, such as zinc coated (or Galvanised), which can be useful where a spring design does not allow a coating to permeate between the coils, or where it gets electronically repelled by the coating process.
Alloy Spring Steels (Silicon Chromes, Chrome vanadium etc)
These are spring steels which are more stable for use at high fatigue levels, and elevated temperatures, such as engine valve springs. Their performance can be greatly enhanced by the introduction of some post forming processes such as shot-peening, where considerable gains in fatigue life may be achieved. Our ability to coil and heat treat in process is beneficial to reducing of the spring notch embrittlement which may occur in the manufacture of some tight index springs manufactured from these materials. Materials of this type, usually have a more prolonged lead time due to material availability, and most requirements are drawn to order. Minimum material draws are therefore a consideration, and so the manufacture of springs from this type of material is usually for those designs requiring higher volumes, or very specialised requirements needing extreme fatigue life or low relaxation at elevated temperatures.
Stainless Steels – Spring quality Stainless Steels are generally referred to as types “302”, “301” and “316” materials. Duplex Stainless Steels and Hastelloys are also often referred to within this class of material, but are not so commonly drawn and therefore are not so readily available. In general, they are more expensive than Carbon Steels with a higher and more volatile price structure due to their high Nickel content. Each grade is engineered for differing physical and mechanical properties, locations and environments. In most cases they have good corrosion resistance to normal environmental conditions, although each grade has its own strengths and weaknesses. They are more resistant to relaxation than Carbon Steels at elevated temperatures, and can be used from cryogenic temperatures up to 400 degrees centigrade, and are often the preferred option due to their relatively low costs compared to more exotic materials such as Inconel and Nimonics. Their relaxation properties are particularly good.
Type 302 Stainless Steel is the most commonly available and is generally available in commonly drawn sizes up to 12.5mm diameter. It can be specified where mechanical stresses are high and good corrosion resistance and relaxation performance are required. It is not recommended in an environment where Chlorine is present. Type 302 Stainless Steels are often used in salt water environments where good mechanical properties are required, but a white layer of whiteish oxidation initially builds up on the surface. Where a good cosmetic appearance is required in these environments, 316 materials are generally specified, but they have poorer mechanical properties.
Type 316 Stainless Steel is often referred to as “J” type Stainless, and has very good corrosion resistant properties, especially in the presence of chlorine or a “Salt Water” environment.
316 Stainless Steel, when polished, retains the bright shiny surface for long periods.
Over many years of experience of both design and manufacture, we use the latest software from IST (Institute of Spring Technology), to evaluate our designs. This enables us to assess theoretical fatigue life, relaxation, stability and stress levels within a particular design. The software allows us to analyse according to the differing International standards, for both design and tolerancing.
We offer a service which is very often free of charge, but we can only emphasise that we can hold a customer’s hand during the design stage, as there may be other unforeseen considerations within an assembly which would effect a springs performance.
An understanding of most International Standards used globally within our Industry is retained.
We can design and manufacture to tolerances used in most countries, as well as supply alternative material standards where required. Some of the design standards we are familiar with are:
BS1726, EN13906, JIS B2704, DIN 2089, IS 7906 SMI 1993.
The various material Standards used are too numerous to mention, with each material sometimes having its own National as well as International Standards.
Reliable Spring has the ability to assemble springs in components where required. We have a light assembly section where we can fulfil our customers’ requirements of light assembly or packaging. Please let us quote for your needs. (Very often a spring is needed in an assembly for delivery direct, as opposed to delivery as a single component).