Invar 36 Round Bar: The Advantages and Applications

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In today&#;s world, the precision of instruments is becoming increasingly important across various industries, such as aerospace, medical, and scientific research. The demand for high-quality and accurate equipment is rising, and the material used in constructing such instruments plays a pivotal role. Invar 36 round bars are an alloy of nickel-iron that has become popular due to their unique properties, making them suitable for various applications. This blog post will explore the advantages of Invar 36 round bars and their applications in precision instruments.

What is Invar 36 Round Bar?

Invar 36 Round Bar is a high-strength alloy steel with excellent corrosion resistance and a low coefficient of thermal expansion. It is often used in aerospace and power generation applications that require components to remain dimensionally stable at elevated temperatures. Despite its hardenable nature, it has good machinability properties and can be welded, brazed, or soldered using various methods. The bar&#;s strength and good formability make it particularly suitable for components that operate at low stresses but must retain their dimensional accuracy over time. It also provides superior wear resistance when subjected to galling or other abrasion-type forces. Its tensile strength ranges from 80 ksi (550 MPa) to 175 ksi ( MPa). Invar 36 Round Bar also remains stable in severely corrosive environments such as industrial acids, alkalis, salts, etc.

Invar 36 Round Bars &#; Advantages and Applications

Invar 36 round bars contain 36% nickel and 64% iron, and their low thermal expansion properties make them an ideal material for use in precision instruments. The thermal expansion coefficient of Invar 36 is minimal, and it remains stable over a wide range of temperatures, ranging from cryogenic to high heat. This makes Invar 36 perfect for applications in which dimensional stability is paramount. Invar 36 is often used in precision optical applications, where dimensional stability is essential and cannot be compromised.

Another advantage of Invar 36 round bars is their high strength-to-weight ratio. Invar 36 is much lighter than steel, yet it boasts better strength characteristics. The lightweight nature of Invar 36 also makes it an ideal choice for applications that require minimal weight and size while maintaining strength and functionality. Some of the applications of Invar 36 include delicate balance wheels in watches, aerospace components, and scientific instruments.

The low thermal expansion coefficient of Invar 36 is suitable for applications in harsh environments with extreme temperature fluctuations&#;for instance, the cryogenic environments in space exploration, satellite communication, and scientific research. Invar 36 also offers excellent magnetic properties, which makes it a favourite material in electronic and magnetic applications. Its low magnetic permeability, and high corrosion-resistant properties make it suitable for use in electrical and electronic equipment like antennas, sensors, and magnetic shielding.

Invar 36 round bars are also easy to work with, making them a cost-effective option for manufacturers. The material is easy to machine, weld, and form, making it an excellent choice for production in high quantities. Its workability allows manufacturers to create intricate components with unparalleled precision, making Invar 36 the go-to material for precision work.

Invar 36 is a nickel-iron alloy with a low thermal expansion coefficient. This makes it ideal for applications requiring dimensional stability, such as in electrical and electronic components, optical instruments, and precision mechanisms. Invar 36 also has a high melting point and strength, making it suitable for vacuum furnaces.

Advantages of Invar 36 Round Bars

The main advantage of Invar 36 round bars is their low coefficient of thermal expansion. This means that they will not expand or contract significantly when exposed to changes in temperature. This makes them ideal for use in applications requiring dimensional stability, such as in electrical and electronic components, optical instruments, and precision mechanisms. In addition to their low coefficient of thermal expansion, Invar 36 round bars also have a high melting point and good strength, making them suitable for use in vacuum furnaces.

Applications of Invar 36 Round Bars

Invar 36 round bars are primarily used in applications requiring dimensional stability. This includes electrical and electronic components, optical instruments, and precision mechanisms. In addition to these applications, Invar 36 round bars can also be used in vacuum furnaces due to their high melting point and good strength.

Machining Invar 36-Round Bars

Invar 36 round bars can be machined using standard methods; however, due to their low coefficient of thermal expansion, care must be taken to avoid excessive tool wear. It is also important to use sharp cutting tools and coolant when machining Invar 36 round bars to prevent them from work-hardening.

Welding Invar 36 Round Bars

Invar 36 round bars can be welded using standard methods; however, due to their low coefficient of thermal expansion, care must be taken to avoid cracking. It is also important to use filler metals with a low coefficient of thermal expansion when welding Invar 36 round bars.

Conclusion:

Invar 36 round bars are a unique material that offers several advantages in precision instruments. Their low thermal expansion properties, high strength-to-weight ratio, and magnetic properties make them suitable for various fields such as aerospace, medical, and scientific research. The ease of workability of Invar 36 also makes it a cost-effective option for manufacturers while delivering precision components. With its significant features, Invar 36 is fast becoming the material of choice for applications that require high accuracy, stability, and dimension control.

In the realm of controlled thermal expansion, there is a new challenger to Invar&#;s long held title. ALLVAR Alloys offer a new approach to solve thermal expansion issues. The similarity in name is no coincidence. Invar is an iron-nickel alloy that exhibits a very low, isotropic CTE (Coefficient of Thermal Expansion) while ALLVAR Alloy 30 is a titanium alloy that exhibits a highly negative, anisotropic CTE. As a result, ALLVAR Alloy 30 is non-magnetic, lower density, and corrosion resistant compared to Invar. As we like to say, &#;ALLVAR Alloy 30 is all the VAR that Invar isn&#;t.&#; 

A Brief History of Low Thermal Expansion Alloys

When discovered in by Swiss physicist Charles Guillaume, Invar&#;s low coefficient of thermal expansion enabled a technological leap in precision instruments that won Guillaume a Nobel Prize . Since its first discovery, various forms and compositions of Kovar, Invar, and Super Invar have been developed and extensively studied. Near Room temperature CTE&#;s for these alloys range from ~0.720 ppm/°C for Super Invar (25°C to 96°C), ~1.6 ppm/°C for Invar (25°C to 96°C), and ~5.2 ppm/°C for Kovar (25°C to 200°C). Invar&#;s thermal expansion coefficient is isotropic, which means it is the same value in every direction. This means a complex component can be machined from a single block of Invar and it will exhibit the same CTE in all directions. 

Since their original discovery in , ALLVAR Alloys have been developed to offer a wide range of thermal expansion values for various products and applications. ALLVAR Alloy 30 was designed to have as negative a CTE as possible with a value of -30 ppm/°C. Using this novel property, designers and engineers can compensate for the natural thermal expansion of other materials in an assembly. For the first time, a designer can choose a CTE anywhere between -30 ppm/°C and the CTE of the most positive material in their system by simply  changing the length of the ALLVAR Alloy component. The tradeoff is that ALLVAR Alloys exhibit anisotropic CTE, which means the thermal expansion is different in various directions. A typical bar of ALLVAR Alloy 30 will exhibit -30 ppm/°C along its length and +31 ppm/°C in the diameter.

Are you interested in learning more about INvar Material? Contact us today to secure an expert consultation!

Machinability and Heat Treatments

To ensure CTE and dimensional stability in service, Invar requires special machining processes that include stress-relieving heat treatments for a consistent CTE in a precision machined part. These heat treatments add significant cost and time to making Invar components. Additionally, Invar is difficult to machine due to rapid wear of cutting tools. While Invar has a relatively low raw material cost, these requirements significantly increase the cost of a precision component. There are several excellent resources available if you need help machining Invar alloys. 

ALLVAR Alloys are easier to machine than Invar components, but there are some things you need to know before machining it. ALLVAR Alloys machine like a beta-titanium. With the right feeds and speeds and a knowledgeable machinist experienced with titanium alloys, it machines well. Additionally, ALLVAR Alloy 30 has a maximum operating temperature of 100°C. Special care should be given to flood the cutting surface with coolant and &#;peck&#; when drilling holes. ALLVAR Alloys are also similar to commonly used wrought alloys like aluminum or normal titanium in that a stabilizing process is required for high precision applications. The ALLVAR team has developed proprietary stabilizing processes for normal (0°C to 50°C), medium (-40°C to 80°C), and extreme (cryogenic to 100°C) operating temperature ranges. If machining titanium is not in your company&#;s wheelhouse and stability is key, ALLVAR can provide your parts already machined and stabilized.  

Operating Temperatures and Corrosion Resistance

The operating temperature range should be considered when choosing either ALLVAR Alloy 30 or any variant of Invar. ALLVAR Alloy 30 is suitable from very cold cryogenic temperatures to 100°C. The material&#;s CTE performance cannot be guaranteed above 100°C.  

The low thermal expansion of Invar, Super Invar, and Kovar is dictated by their magnetic properties. Therefore, they lose their low thermal expansion when cooling to colder temperatures or going above their Curie temperature. For example, Super INVAR can lose its low CTE properties at very low temperatures, while Invar-36 will drift away from its low CTE outside a -70 to 100°C temperature window. 

Invar is very susceptible to corrosion if not handled properly and components typically require nickel plating or other coatings to prevent corrosion in service. ALLVAR Alloys on the other hand have excellent corrosion resistant properties like other titanium alloys. ALLVAR Alloys can also be anodized and coated like other titanium alloys. 

Should you use Invar or ALLVAR Alloys?

It depends on your application! Each alloy has its advantages for specific applications. If Invar&#;s low thermal expansion works and you need the same isotropic thermal expansion properties in every component direction, INVAR is likely better suited for your project. If your goal is to target thermal stability in one direction or compensate for thermal mismatch of dissimilar materials, consider using ALLVAR Alloy 30.  

Still unsure if Invar or ALLVAR Alloys are better for your project? We are a team of materials scientists at heart. Whether it is Invar or ALLVAR Alloys, we would love to help you find the right material for your next project. Please contact us by clicking the orange button below and we will steer you in the right direction. Your success is what&#;s most important to us.  

We are also happy to provide a spec-sheet with example CTEs across a wide range of temperatures or if you are interested in our experimental ALLVAR Alloys with higher upper operating temperatures.

Don&#;t forget to follow ALLVAR on our LinkedIn page, check out our YouTube page, and subscribe to our newsletter to stay up to date with our latest news and events! As a team of passionate material scientists and engineers, we would love to connect and answer any questions you may have about our revolutionary material. 

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