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Kovar

Kovar is an iron-nickel-cobalt steel alloy and a trademark of CRS Holdings. To produce high quality Kovar, its chemical composition must be controlled within narrow limits, typically the alloy must contain 29% nickel and 17% cobalt. So, for this reason, strict quality controls need to be employed in its production.

Properties

The biggest advantage of Kovar for industry concerns its controlled expansion properties, i.e., when heat it applied it expands far less than other metals and alloys. In fact, its expansion properties are comparable to Pyrex (or borosilicate) glass and alumina ceramics. It has good properties for machining and deep drawing and it is also porosity-free. Kovar’s magnetic properties depend upon the production method used.

Production

During fabrication, Kovar is annealed in a furnace with a controlled atmosphere consisting of nitrogen or ammonia. Temperature isn’t critical during the annealing process, but when the procedure is complete, the temperature of the furnace should be reduced to less than 175°C to avoid thermal shock or oxidation, as over-oxidation will result in poor glass-metal bonding.

Kovar is available in seamless or welded in pipe, tube, bar, wire, sheet, plate, flanges and forgings.

Applications

Being a controlled expansion alloy, Kovar is ideal for hermetic sealing applications. For this reason it is important in the production of various electronic and electrical components.

  • Transistor/power tubes and diodes
  • Scientific and laboratory instruments
  • Sealing applications, such as attaching glass to metal, or ceramics
  • Light bulbs

Interesting Fact

Kovar is important in the production of X-ray tubes for medical facilities and other uses.

Specific gravity……………………………….. 8.36 Curie temperature
Density     °F……………………………………………. 815
   lb/cu in……………………………………… 0.302     °C…………………………………………… 435
   kg/cu m…………………………………….. 8359 Melting Point
Thermal conductivity      °F………………………………………….. 2640
   Btu-in/ft²/hr/°F…………………………….. 120      °C…………………………………………. 1450
   W/m-K………………………………………. 17.3 Modulus of elasticity
Electrical resistivity      psi x 10(6) ………………………………. 20
   ohm-cir mil/ft………………………………. 294      MPa x 10(3) …………………………….. 138
   microhm-mm……………………………….. 490

 

Recent Ads in Kovar

Kovar Sheet

Offcut Length: 700mm
Offcut width: 300mm
Thickness: 5.0mm
Cut Type: Flat