About Invar and Kovar

Invar, commonly known as FeNi36 (64FeNi), is a nickel-iron alloy, also known as Invar, invariant steel, and expansion alloy. It is known for its unique low coefficient of thermal expansion (CTE or α). This property makes it extremely valuable in industries that require high dimensional stability even under temperature fluctuations. In addition, it has the characteristics of low thermal conductivity, high toughness, high cross-sectional shrinkage, good ductility, low strength and hardness, and good plasticity, making it an important structural material.

4J36 (Invar alloy) grade comparison

Kovar alloy is a sealable alloy of iron-nickel-cobalt system with a coefficient of expansion close to that of hard glass within a certain temperature range. This property makes it compatible with some glass or ceramic materials.

Machinability of Invar and Kovar Precision Parts

Machinability refers to how easily a material can be machined using machine tools. This is an important aspect to consider in the field of manufacturing and production, which affects cost-effectiveness and the quality of the final product. The more machinable a material is, the more suitable it is for high-speed precision machining processes. Factors that affect material machinability include hardness, strength, ductility, brittleness, thermal conductivity, work hardening tendency, melting point, chemical stability, etc.

Invar alloy has excellent machinability and is suitable for precision part production. Its low coefficient of thermal expansion and high dimensional stability help it to maintain tight tolerances during machining. The machinability of Invar alloy ensures the production of high-precision parts that meet the stringent requirements of various industries such as aerospace, defense and scientific instrumentation.

Kovar alloy is known for its unique characteristics, such as excellent mechanical properties and controlled coefficient of thermal expansion, but it also poses various machining challenges. The inherent hardness and strength of the material increase the forces required for cutting or forming, which adversely affects its machinability. However, these attributes are also very suitable for precision part production, making it an ideal choice for applications in industries such as aerospace and electronics.

High nickel content enhances the stability of Kovar alloys, but requires the use of specific cutting tools, lubricants and appropriate feed rates to control mechanical strain during processing.

Conversely, these properties make it particularly useful for manufacturing electrical vacuum tubes, as its low coefficient of expansion enables it to conform precisely to glass and ceramics at different temperatures.

For example, in semiconductor packaging, Kovar is widely used because its dimensions change predictably over a wide temperature range, ensuring that electrical components can operate reliably even in harsh environmental conditions.

Summary

Invar has excellent dimensional stability over a wide temperature range, making it ideal for applications requiring high-temperature components or thermal stability.

Kovar exhibits excellent solderability and low thermal expansion compatible with hard glass, making it ideal for electronic products such as vacuum tube sealing.