What is Invar: Definition, Properties,Types & Applications

There are different types of metals and their alloys, and they are used in different applications. Invar is also a metal alloy that fulfills the requirements of diverse industries. If you want to incorporate Invar in your components and learn about it, this guide below can be of great help. So, let's read.

Qu'est-ce que l'Invar ?

Invar is an alloy of iron and nickel known for its low thermal expansion. It is equipped with various properties, and the best one is that it contracts and expands minimally when there is a temperature change. Hence, it is used in industries where dimensional stability is required. It is also opted for applications where precision machining is needed to manufacture components having tight tolerance.

A Brief History of Invar

Invar was invented in Paris by Charles Edouard Guillaume in 1986. The first letter of Invar is always written in the capital because it is associated with the trade name of a company Imphy alloys, which is a French company. This company originated in a small city of France and the alloy was industrialized in this company once it was invented.

What is Invar Made of?

Invar is an alloy composed of different materials, nickel and iron being the highest quantities. Nickel is about 36% and is opted for due to its low thermal expansion. The amount of iron contained in Invar is 64%, which gives the alloy its structural framework. There are other elements, like carbon, molybdenum, and chrome, that enhance the properties of Invar.

Properties of Invar Steel

Invar is opted in distinct applications for its excellent properties, and some of these are as follows:

Low Thermal Expansion

Invar steel offers low thermal expansions, which makes it suitable for applications where the margin for dimensional changes is minimal.

High Dimensional Stability

The stability of Invar makes it suitable for applications that require high precision. The size and shape of Invar are maintained under variable temperatures at all times.

Toughness and Strength

Invar has high strength and toughness. Therefore, it is suitable for applications that need strength and precision and is mostly opted for mechanical and structural components.

Résistance à la corrosion

Invar is moderately corrosion resistant, and if it is used in a high moisture environment, it may need secondary finishing processes involving coating.

Different Types of Invar

Invar alloy has various types, and each type has different characteristics, compositions, and applications. Some of these types are as follows:

Invar 36

Invar 36 has 36% nickel and 64% iron and has zero- coefficient of thermal expansion at room temperature. It is used in precise instruments and devices that need dimensional stability, like creep gauges, clocks, and thermometers.

Super Invar

Super Invar has a high nickel content and a very small amount of cobalt added. It has a very low thermal expansion through a wide temperature range. It is highly critical in high-precision instruments used in aerospace and satellite components.

Invar 42

Invar 42 has 42% of nickel, and the remaining proportion is of iron. It has high thermal expansion, like glass, and is used in various electronic applications, such as light bulbs and vacuum tubes.

Invar 48

Invar 48 has 48% nickel, and the rest is iron. It has a thermal expansion that matches ceramics and is used in electronics for metal to ceramic seals like in transistor enclosures.

Invar K

Invar K, also known as Kovar, has 29% nickel, 17% cobalt, and the rest iron. It has a very low thermal expansion and has characteristics of borosilicate glass. It is used in CRTs, vacuum systems, and microwave tubes.

Invar 6

Invar 6 has less nickel, which means it has high thermal expansion but still better dimensional stability. It is used in applications where expansion is needed but in a controlled way. It is mostly used for special precision instruments.

How is Machining with Invar?

Machining Invar is challenging because it may get hard and lead to tool wear. However, the low thermal expansion makes it suitable for precision applications. It is important to carefully set the tool's sharpness and cutting speed, ensuring that proper heat management methods are incorporated.

The use of coolants and chip control mechanisms is crucial for clean, precise cuts without damage to the component surface.

Applications of Invar Steel

Invar steel is used in many applications, and some of these applications are discussed below:

Precision Instruments

Precision industries, which use measuring tools, are made using Invar as it offers low thermal expansion and accurate readings.

Aérospatiale

The aerospace industry uses Invar steel for components, which comprise fixtures for precise alignment and satellite structures. It offers dimensional stability and maintains the integrity of the components when they are used in varying conditions of the environment.

Électronique

In electronic applications, Invar is used to manufacture electronic housing and devices. The components that need less thermal expansion and stable dimensions are manufactured using it.

Metrology

In metrology applications, the precision of measurements is crucial. The low thermal expansion offered by Invar ensures the accuracy of tools under varying temperatures.

What are the Advantages of Invar

There are versatile advantages of incorporating Invar into applications, and some of these are as follows:

• Invar offers high dimensional stability, and high-precision applications can make the most of it.
• It has excellent temperature stability irrespective of consistent fluctuations in temperature.
• Invar is versatile, and from aerospace to metrology, it can cater to every industry.
• It is durable and tough; hence, the components manufactured last longer.

What are the Limitations of Invar

Invar also has some downsides, which should be considered when incorporating into the applications. These limitations are as follows:

• Invar has poor machinability, leading to issues with tool wear and chip control.
• It has low mechanical strength when compared to other alloys, which limits it for some stress-oriented applications.
• It has moderate corrosion resistance and requires secondary treatments to enhance resistivity.
• Invar is highly expensive compared to other alloys as it has a specialized composition.

Conclusion

As you have read the guide above you must have learnt what is Invar and where it can be used. Now, choosing this alloy for your project must be much easier because you know the details about it.

Start Your CNC Machining Invar Project with DEK

You can start your upcoming projects with Invar components by considering DEK as your manufacturing partner. We have experience in machining Invar and manufacturing high-quality components, which can benefit you in the long run.

Common FAQs about Invar

Why is Invar so expensive?

Invar is an alloy that has Iron and Nickel in its composition, making it expensive.

Is Invar magnetic?

Invar offers magnetic properties when it is below the Curie Point and non-magnetic properties above the Curie Point temperature.

Does Invar expand on heating?

No, Invar does not expand on heating due to the presence of nickel in its composition.

Is Invar hard to machine?

Yes, compared to other alloys, Invar is difficult to machine.

What is the difference between Inconel and Invar?

Invar is an alloy consisting of iron and nickel, while Inconel has chromium and nickel.