Although certain materials have been regarded as a spring material, not all are specially designed alloys for spring use. An ideal spring material will have properties of high strength, high elastic limit, and low modulus. Because springs are inherently resilient structures, they are designed to experience large deflections, requiring an extensive elastic range. Other characteristics, such as corrosion resistance, fatigue strength, formability, electrical conductivity, magnetic permeability, availability, and cost, are also considered in light of cost/benefit. Because they require so many diverse characteristics, stainless steel springs are emerging as the most popular.
Although not clearly delineated through national specifications, surface quality also has a major impact on fatigue strength. For fatigue applications, it is best to utilize materials with high surface integrity, particularly in the high cycle region.
In recent years, stainless steel springs have gained an impressive popularity, due to its special characteristics. One of the most common reasons for selecting steel springs for industrial use is its corrosion resistance. Stainless steel springs resist chemicals and rust, making them the ideal choice for industrial and processing industries.
Stainless Steel – The Wonder Material
Scientists around the world consider stainless steel to be an astounding material perfect for many different types of applications. Harry Brearly was one of the first to notice that gun barrels didn’t rust when they were left out in the rain. Upon taking the barrels to a lab, it was discovered that they contained 13% chromium, which attributed its anti-corrosive property. This exciting news marks the discovery of stainless steel as a wonder material, and was published in the New York Time’s 1915 publication. Stainless steel has been the optimal choice for a variety of industries and applications ever since.
The Making of Stainless Steel Springs
Springs are found in almost every industry around the world. Stainless steel is one of the most favored spring materials because of its high yield strength, resistance to rust, and durability. Steel springs are typically crafted from wire that has been tempered and hardened to best suit the needs of the type of spring it will become.
Steel springs begin as a large metal bar, which weighs several hundred pounds. As the metal bar is heated for malleability, steel is drawn out through a series of dies, gradually decreasing until they reach a size that is suitable diameter for the manufacturing of springs.
There are two different types of steel used in spring manufacture. Carbon steel, which is well known for its quality and uniformity, often becomes music wire. However, steels crafted from carbon are susceptible to rusting. For this reason, stainless steel is generally recommended in industrial industries, or any areas that have the possibility of coming in contact with water.
Here are the most common types of stainless steel springs, which can be crafted to meet the needs of any diameter or length:
- When at rest, extension springs crafted from stainless steel are tightly coiled. When extended, they exert the highest levels of mechanical energy.
- Compression springs are the opposite of extension springs. These stainless steel springs are at rest when they are fully extended, and contain the highest amount of stored energy when they are compressed.
- Torsion springs crafted from stainless steel are also tightly coiled like extensions springs. However, their force is created by torque or twisting.
Types of Steel Springs and their Applications
Stainless steel, including 10% chromium, offers an excellent source of corrosion resistance in harsh environments. In recent years, many new variants have improved its temperature resistance. Stainless steel is generally classified into four types – austenitic, precipitation hardening, martensitic, and ferritic. Typically, precipitation hardening and austenitic steels are considered to be the most ideal materials for spring use.
Here are some of the popular precipitation hardening steels and austenitic materials used in spring construction.
300 Series Stainless Steel:
This austenitic stainless steel variant is alloyed with 17-25% chromium and 10-20% nickel. The nickel that is present improves its ductility and durability, in addition to contributing to its excellent corrosion resistance. Because of its anti-corrosive property, this type of stainless steel is often used in marine construction. Bridges, harbours, and ports require a solid foundation so that they can withstand the impact of heavy loads of containers and vehicles. For the construction of such structures, a piling company needs to be contacted which often uses steel and concrete combinations for inserting piles into the sandy ground. These piles are considered strong enough to support any superstructure built above them. Hence, different variants of steel are usually used to give strength to any building. The 300 series is generally hardened by means of cold working. It is not hardenable through heat treatment.
Stainless Steel Type 302:
Stainless steel 302 is ductile and austenitic, in addition to being strong. This stainless steel type is another heat resisting steel variants that is strengthened through cold working. Type 302 springs have a silver graycolor, and are used in cryogenic, pressure-containing, sanitary applications.
Stainless Steel Type 304:
This non-magnetic alloy can withstand extremely high temperatures. Stainless steel type 304 offers one of the strongest known resistance against corrosive acids. Thus, springs type 304 are used throughout a variety of applications that come in contact with corrosive acids. Additionally, steel type 304 holds low measurements of carbon, which helps in avoiding carbide precipitation. The springs that are manufactured from this variants are largely used in chemical, cryogenic, dairy, pharmaceutical, and food industries.
Stainless Steel Type 316:
This stainless steel alloy holds a carbon content lower than that of stainless steel type 302. This is especially useful in welding applications that require lower carbide precipitation. This stainless steel variant works to provide an extra resistance to corrosion due to its higher molybdenum content. Type 316 stainless steel springs are most suitable for industries that demand highest levels of hygiene such as pharmaceuticals and food, in addition to sub-zero temperatures and even marine environments found in piping of oil and gas industries. This variant is distinguishable in appearance due to its silver gray color.
Stainless Steel Type 301:
Type 301 is hardened through cold working, and is not hardenable through heat treatment. It can achieve high tensile strength and ductility through cold working. This stainless steel type is not magnetic in the annealed condition, but does become magnetic following the cold formation.
Stainless Steel 17-7:
17-7 stainless steel springs are favorable in the fact that they can withstand even higher temperatures than type 302 or 316. This steel is alloyed with aluminium, nickel, and chromium. The max temperature limit in this stainless steel spring is 343 C (650 F).
Stainless steel spring application can be found across a myriad of industries. Their manufacture and production provide safe support for business in all types of verticals, including oil and gas piping, industrial machinery, electronic components, defense and aerospace mechanisms, and much more.