Coil springs can be manufactured through either cold wound or hot wound coiling processes.
In hot wound coiling, the material is heated to austenitic temperatures of over 1550F, formed on the coiler, and then quenched in oil to form martensite. Next, the springs are tempered to change the microstructure to a tempered martensite which provides strength to achieve the desired spring performance and ductility to withstand the operation. Hot wound coiling is usually for larger bars sizes over 0.500” (12 mm). MW's Greer location can coil bars up to 3.00” (75 mm) in 5160H, 51B60H and 4161H material. Additional materials, such as Inconel and Stainless Steel, can be coiled through hot winding, but these materials are not included in our standard raw material inventory.
MW Components utilizes a continuous heat-treating process to manufacture hot coiled springs. Every bar and every spring in a lot goes through the entire length of the furnaces. This means that each bar, and therefore each spring, gets a consistent heat treatment and is not dependent on its position in the furnace. This is a distinct advantage over batch processes where each spring receives a different heat treatment depending on where and when the material is placed in the furnace.
Cold coiled springs are made from fully heat-treated material and then stress relieved to remove the stresses induced during the coiling process. MW Components - Greer: Springs can coil up to 0.625” (15.8 mm) in Chrome Silicon and Oil Tempered Wire. MW can also coil high tensile Chrome Silicon to 0.437” (11 mm) and in 2019 we will extend our range for high tensile Chrome Silicon over 0.625” (15.8 mm).
Since many products rely on the durability of their spring components, it is crucial to select high-quality springs that will not fail prematurely. Untimely spring malfunction can be the result of several factors, which include poor design, the use of low-quality materials, or an inferior manufacturing method. Although spring may seem like a minor component within a larger device, functional failure of the spring could result in device malfunction. This is why the quality of the materials being used to produce a spring and the manufacturing process should be taken into consideration before making a purchase.
Springs are generally made of hardened steel. The spring manufacturer has the option of using either pre-hardened steel before forming the spring, or they can also harden the spring after the formation process. The most commonly used spring steels are music wire, stainless steel, chrome silicon, oil tempered wire, and chrome vanadium. The different materials are ideal for a number of different conditions. Below are some materials and their specific conditions:
Step One – The manufacturing process starts with coiling the spring. This can be done with either cold or heated wire. Cold winding starts with a wire that is at room temperature and involves winding the wire around a shaft. The process of hot winding is used for thicker wire or bar stock. The metal is heated beforehand to increase wire flexibility and then the steel is coiled around a shaft while it is still extremely hot. After it has been coiled, it is immediately taken off of the shaft and dipped into the oil so that it can cool and harden at a rapid rate.
Step Two – Once this step is complete, the steel needs to completely harden. The coiling process causes stress in the wire, which is alleviated by heat treatment. The spring is heated in an oven for a specific amount of time at a set temperature and then placed aside to cool slowly.
Step Three – The following step is called shot peening and using a machine to strengthen the steel to prevent metal fatigue, which could cause cracking during its use.
Step Four – The next step is called setting. It sets the spring to function correctly and remain stable at a certain length. During the process, it is completely compressed, usually multiple times, so that all the coils are completely pressed up against their bordering coils.
Step Five – The final step in the creation of the spring is usually coating. This is done to prevent corrosion, and the whole surface of the spring is coated with liquid rubber or plated with another metal such as chromium or zinc.
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