- Grade / Alloy
- Kovar
- EN / W.Nr.
- 1.3981
- AISI / SAE
- —
- UNS
- K94610
- Family
- Controlled expansion
Chemical composition
Chemical composition
Typical compositionTypical composition of the principal alloying elements; not a complete acceptance analysis.
| Element | Content (% by mass) |
|---|---|
| NiNickel | 29.6 |
| FeIron | 53 |
| CoCobalt | 16.9 |
Values describe the grade, not the analysis of a specific batch. The applicable product specification and material certificate determine acceptance. A dash does not mean zero.
Why Kovar is used
Kovar is known for precision connections combining metal and glass. As an electronic component heats and cools, movement in each material affects the joint. The iron-nickel-cobalt composition of Kovar provides expansion behaviour compatible with certain hard glasses. This matching helps reduce stresses created at their interface by temperature changes.
Hermetic electronic connections
Electronic packages, power tubes and microwave components illustrate its applications. Glass or ceramic can provide insulation while metal forms the connection and supporting portion. Hermetic joints are sealed connections used to separate the internal environment from external influences. Kovar serves the metal side, with expansion compatibility contributing to the function of the joint.
Invar and Kovar
Invar 36 is known for precision mechanical parts requiring very little dimensional change with temperature. Kovar instead emphasises expansion compatibility with the glass or ceramic in a joint. Cobalt distinguishes its composition from iron-nickel Invar. Low expansion alone therefore does not explain their different roles: the movement of the joined material matters as well.
Names and product forms
Kovar is also identified as 1.3981 and UNS K94610. Wire and rod can serve connection elements, while flat products suit enclosure and package parts. Working together with other materials is the common theme from electronic feedthroughs to closed component bodies. Its value centres on physical compatibility through temperature changes rather than exceptionally high load capacity.
Typical application areas
Electronic enclosures, glass-to-metal feedthroughs, tube connections.
Product and cutting options
Relevant product forms for this material are listed below. Availability varies with grade and dimensions.