A286 Alloy Springs

A286 Alloy Springs

A286 is non-magnetic and possesses a level of aqueous corrosion resistance comparable to that of the austenitic stainless steels. A-286 can attain high strength levels when aged after cold work, and has wide application in high-temperature fasteners and springs.

A286 Alloy Springs FAQs

What is A286 and why is it used for springs?

A286 is a precipitation hardening austenitic iron-nickel-chromium alloy, not a true nickel-base superalloy. CTI's specification table gives the nominal composition as chromium 13.50 to 16 percent, nickel 24.0 to 27.0 percent, molybdenum 1.0 to 1.50 percent, and titanium 1.9 to 2.35 percent, with iron making up the balance. Density is 0.286 lb./in3 and modulus of elasticity is 28.8x10^6 psi. The alloy reaches high strength when aged after cold work, stays austenitic and non-magnetic, and offers aqueous corrosion resistance comparable to the austenitic stainless steels.

Why choose A286 instead of a nickel-base superalloy like Inconel 718?

Cost and availability, when the temperature requirement allows it. A286 is iron based with roughly a quarter nickel, so the raw material price is well below that of a nickel-base alloy where nickel is the balance. It is also easier to procure and easier to process. Inconel 718 carries higher strength and a higher usable temperature, and it costs accordingly. If your spring operates within the range on CTI's table and does not need 718's strength, A286 delivers the precipitation hardened performance and the non-magnetic austenitic structure at a materially lower cost per part. Over-specifying the alloy is a common source of avoidable spend.

What is the maximum service temperature for an A286 spring?

CTI's technical specification table lists a Max Temp of 700°C (1300°F). In practice, sustained load capability falls off before that ceiling, and many aerospace fastener and spring applications treat roughly 1200°F as the working limit for parts that must hold load without measurable relaxation. The governing question is stress relaxation at your actual temperature and hold time, not the maximum number the material will tolerate. Give the operating temperature, the duration at temperature, and the allowable load loss, and the design stress can be set against relaxation data rather than against a room temperature strength figure.

What is the minimum wire size for A286 springs?

The specification table lists a Min Size of 0.018 in (0.45 mm). That minimum is noticeably larger than the 0.005 in floor CTI lists for several of the nickel and cobalt alloys, which is worth catching early if your design calls for very fine wire. A286 work hardens quickly and is stiffer than stainless grades 316 and 310, so the practical section is governed by what can be coiled and aged without cracking. If the required load and envelope drive you below 0.018 in, that is a material selection conversation, not a tolerance conversation.

What heat treatment does an A286 spring need after coiling?

A286 develops its properties from a combination of cold work and precipitation aging. The titanium addition forms a gamma prime type precipitate during aging, and because the alloy is cold drawn and then coiled, the aging cycle both strengthens the part and relieves residual forming stress. Aging temperature and time determine final strength, so the condition should appear on the drawing rather than being inferred. Coiling Technologies performs heat treating in house in Houston, which keeps the aging cycle documented against the same part record as the coiling parameters and inspection results.

Are A286 springs non-magnetic, and how corrosion resistant are they?

A286 is austenitic and non-magnetic, which is why it turns up in instrumentation, sensor housings, and any assembly where magnetic permeability is a design constraint. Its aqueous corrosion resistance is comparable to that of the austenitic stainless steels, so it performs adequately in general atmospheric and mild chemical exposure. It is not a substitute for a cobalt-nickel alloy or Inconel 625 in chloride pitting, seawater, or sour gas service. Heavy cold work in a spring can raise permeability slightly at the most deformed sections, so state the magnetic requirement explicitly if a low permeability limit applies.

What industry standards might a customer specify for A286 spring material?

A286 is covered by UNS S66286 and appears in several AMS and ASTM documents your engineering group may already call out, including AMS 5731, AMS 5732, and AMS 5737 for bar and wire product forms and ASTM A453 Grade 660 for bolting material. Customers also specify heat treat condition callouts and their own internal material specifications. Coiling Technologies can build and heat treat to the requirements you supply and provide material certifications with chemistry and mechanical property data showing conformance. Put the specification and revision on the drawing so the incoming material is purchased against the correct document.

What information should I provide to get an accurate A286 spring quote?

Send an engineering drawing if you have one. If you do not, CTI's engineering team can develop the design from performance requirements. Useful inputs are the load and deflection or the required spring rate, the working and solid heights, the installed and working envelope including hole and shaft diameters, the operating temperature and dwell time, the expected cycle count, the environment, any magnetic permeability limit, the required aging condition, applicable AMS or ASTM specifications, and the documentation package you need. Quantity and the need for a prototype before production affect how the job is planned.