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Invar 36 Spotlight

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Invar 36[1], also known within the industry as Nilo 36[2], is a nickel-iron superalloy known for its low coefficient of thermal expansion. Containing 36% nickel, it maintains nearly constant dimensions as well as good strength and hardness over a wide range of temperatures. Invented in 1896 by Swiss physicist, Charles Edouard Guillaume, Invar was created as a low-cost solution to a meter once made of platinum and iridium. Guillaume’s work led to the discovery of a fairly inexpensive iron-nickel alloy—a steel-like material—that expands very little when heated. He named the alloy Invar because it was almost unchanging or "invariable.”

Invar [3] is typically machined, but what many people don’t know is that it can be cast. 


Invar 36 Success

One of our customers came to us specifically wanting to use INVAR 36 for a component requiring the near constant dimensions and long-term dimensional stability this alloy is known for. Due to confidentially agreements, we cannot name the customer but what we can tell you, is that like with many other projects, Signicast engineers rose to the challenge to not only cast Invar 36 successfully but completely exceeded the customers’ expectations—all while saving them money. Because after all, isn’t that the end goal? Create a quality component at the lowest total cost. 

 >> Discover your solution.

Why did our customer need Invar 36? The slightest change in dimension or shape of their component could alter their end product—even though they were already in a temperature controlled room. A few degrees could alter the function of the part. They knew they needed to work with a material like Invar 36 but machining it from solid became costly.

How did Signicast help? We had never worked with Invar 36 in the past, but there has never been a challenge our engineers didn’t at least try to overcome. With some research and testing we came up with a casting material that actually performed as good or better than wrought and we were able to cast net-shape successfully. Not only did we add savings on final part cost because they didn’t have to machine the part, but our final part cost was actually cheaper than their original block of metal—prior to machining.

The end result? A very happy customer who saved tenfold and a new material added to our offerings.  

Invar 36 maintains nearly constant dimensions at temperatures below -150 degrees Celsius up to 260 degrees Celsius.

Who Should Use Invar 36?

Customers who are under strict temperature constraints will likely see the advantages of using Invar 36. Unfortunately, those who are currently machining from solid do not realize that casting net-shape is even an option. In today’s world, Invar 36 is often used in measuring devices, precision mechanical systems, laser components, thermostat rods, meters and components that transport liquefied gases—to name a few.

Material Units Invar 36 304 Stainless Steel
Density g/cm3 8.05 8.00
Young's Modulus GPa 141 193
Poisson's Ratio -- 0.26 0.27
Microyield Strength MPa 70 >300
Thermal Expansion Coefficient x 10-6 K-1 1 14.70
Thermal Conductivity W/m K 10.40 16.20
Specific Heat W s/kg K 515 500
Specific Stiffness -- 17.50 24.10
Thermal Diffusivity 10-6 m2/s 2.60 4.10
Thermal Distortion (Steady State) µm/W 0.10 0.91
Thermal Distortion (Transient) s/m2K 0.38 3.68

Advantages of Invar 36

The most obvious advantage of Invar 36 is its ability to hold dimensions at cryogenic temperatures. Aside from that, Invar 36 looks and feels similar to steel. It also has outstanding weldability and machinability. Invar can also be created with customized chemistries to better meet the strength and hardness needs of customers. 

Whatever your situation, our expert engineering staff is ready to listen. With 30 in-house engineers, we partner with you on every project to ensure your component is the highest quality possible. Contact our engineering team today to get the conversation started.  

 

1* Invar 36 is a trademark of Carpenter Technology, Reading PA
2* Nilo 36 is a trademark of Special Metals Corporation, USA
3* Invar is a trademark of Imphy Alloys, France

 

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Last updated 11.27.2019