Metal Springs: Your Guide to Compressor Spring Materials
When it comes to developing metal springs for compressors, several factors have to be taken into account. Your choice of custom springs will differ depending on your environment, industry, and other variables.
The type of environment that the spring will be subjected to, as well as the type of industry the spring will be used in are both critical dynamics to consider when determining the best option of what type of metal to be used in a custom metal spring.
Which Type of Metal Springs is Right for Me?
Below is a guide to what types of metal are commonly used and what considerations to make when developing metal springs for compressors.
A deep analysis of the strengths of each type of metal is included. A higher cost, more durable metal is not always required.
Understanding when different metal materials should be utilized can help ensure that the correct springs are always employed.
17-7 PH Stainless Steel
17-7 PH stainless steel springs offer minimum warping when placed under extreme temperatures up to 600 degrees Fahrenheit (316 degrees Celsius). It offers exceptional fatigue properties that are superior to standard stainless steel chromium types. The formability of 17-7 PH is good and must be cooled slowly due to its rapid hardening.
17-7 PH stainless steel also offers good corrosion resistance. However, it can be out lasted in corrosive environments by chromium-nickel types of stainless steel. This class of stainless steel is considered able to be welded by both the resistance and the common fusion technique.
However, 17-7 PH is not as fit for welding as other alloys in this stainless steel class. Weld slag can form as well as penetration degradation due to the 17-7 PH alloy having a high AI content.
High hardness can be met allowing for great strength to come from 17-7 PH stainless steel. Using specific fabrication techniques, such as intermediate annealing, in the formation of intricate parts can produce an extremely hard and strong material that can offer a variety of metal spring uses within compressors.
Inconel 718 and Inconel X-750
The alloys that make up Inconel 718 and Inconel X-750 are resistant to both corrosion as well as oxidation when used in the formation of metal springs. Commonly employed in high temperature applications, Inconel X-750 is well suited for use in extreme settings.
This resistance assures that these alloys will withstand exposure to a variety of harsh environments.
Consisting of a Nickel-Chromium structure, Inconel X-750 can defend itself from heat damage. When the temperature around it increases, the surface of Inconel X-750 is protected by the formation of a thick oxide layer that provides a stable cover to prevent any damage from occurring to the alloy.
This feature allows for Inconel X-750 to withstand temperatures up to 700 degrees Fahrenheit-1020 degrees Fahrenheit (370 degrees Celsius-550 degrees Celsius).
Having a high creep-rupture strength, Inconel 718 can effectively be used as metal springs in a variety of industries. Being able to hold up in harsh environments makes Inconel 718 a great alloy use in the following:
- high temperature fasteners
- components in nuclear pressurized reactors
- high level functioning exhaust systems
- combustors and steam generators
- heat exchanger tubing
- gas turbines and natural gas processing with corrosive contaminants such as sour gas (H2S)
- pressure vessels and chemical processing
Very high temperature situations for springs would warrant the use of Inconel X-750 over Inconel 718. Specific heat treating fixtures, applications for nuclear power plants, the formation of tools, and use within jet engine parts are higher intensity environments where springs made from Inconel X-750 would be required.
An alloy comprised of Nickel-Chromium-Cobalt, Nimonic 90 is equivalent to Inconel in properties relating to corrosion resistance. Though less elastic than Inconel, Nimonic 90 is a more rigid alloy. It can offer a higher approximate tensile strength when used in metal springs.
Nimonic 90 is used in applications of high temperatures when properties utilizing better strength are required. A higher strength property in a high temperature environment include springs inside exhaust nozzles and turbine blades on jet engines. In these instances, not only is the temperature high, but the pressure is also extreme.
A Nickel-Molybdenum-Chromium alloy with Tungsten, Hastelloy C-276 use in metal springs moves beyond the good corrosion resistance boasted by previous listed metals. Instead, it offers a level of excellent corrosion resistance. Crevice corrosion and pitting are examples of extreme corrosion that Hastelloy C-276 is especially resistant towards.
Less ideal than Nimonic 90 or Inconel in extreme high temperature applications and offering less elasticity, Hastelloy C-276 is better utilized in springs that perform in processes using acid or halide catalysts.
Pharmaceutical and food processing equipment as well as ducting and scrubbers used in flue gas desulfurization are typical applications of Hastelloy C-276. It stands well in both petrochemical and chemical organic chloride administrations.
As an age hardening Cobalt-Chromium-Nickel alloy, Elgiloy has a combination of good mechanical properties including ductility and high strength when used in metal springs. When a low relaxation of high temperatures is required and a high resistance to corrosive materials is necessary, Elgiloy is utilized.
Its age hardening components and mechanical force-deflection properties also allow for an exceptional fatigue life. This ensures Elgiloy will withstand harsh environments and perform as needed.
The medical technology industry is highly serviced by Elgiloy metal springs. Its use in medical devices and dental products is typical due to the high resistance to corrosion offered by Elgiloy. Also, the fact that it is non-magnetic is appealing in the use of medical equipment. This is because several parts of imaging equipment and other medical devices can be skewed by the presence of magnetic materials.
When determining what metal springs to use for a compressor, the previously listed metals have specific roles to fill.
Whether being used in an industry that performs within high temperature settings or an industry that will expose a compressor to corrosive environments, springs can be customized in a way to most efficiently suit the needs of the compressor being used.
The specific function of the metal spring and what it will be exposed to is considered to ensure the best materials with the most efficient properties will be used in the formation of custom springs.
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