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Kovar Alloy

Kovar AlloyKovar AlloyKovar AlloyKovar Alloy

Product Introduction

Kovar alloy, ASTM F15, Nilo-K,UNS K94610(FeNi29Co17),Chinese 4J29
Kovar Alloy, is a controlled expansion alloy. It is a Nickel Iron alloy with 29% Nickel, 17% Cobalt and the remaining balance is Iron.
Forms: Sheet/Plate, Bar/Rod/Wire/Coil,Capillary/Pipe/Tube

Product details


Kovar Alloy is a vacuum melted, iron-nickel-cobalt, low expansion alloy whose chemical composition is controlled within narrow limits to assure precise uniform thermal expansion properties. Extensive quality controls are employed in the manufacture of this alloy to ensure uniform physical and mechanical properties for ease in deep drawing, coining, stamping and machining.


Kovar alloy has been used for making hermetic seals with the harder Pyrex glasses and ceramic materials. This alloy has found wide use in application where high reliability is a necessity. In power tubes, microwave tubes, transistors, diodes, inter-grated circuits and has been used for the flat pack and the dual-in-line package.


Cross Reference

Russia USA UK Japan France Germany
29HK Kovar Nilo K -
Dilver P0 Vacon 12
29HK-ВИ Rodar Teachallony Glass 29-17 Teleaseal -
Dilver P1 Silvar

Typical chemistry

C P S Mn Si Cu Cr Mo Ni Co Fe
0.03 0.020 0.020 0.50 0.30 0.20 0.20 0.20 28.5-29.5 16.8-17.8 Balance

Physical Properties

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

Mechanical Properties

Tensile Strength Ksi MPa 75 518
Yield Strength Ksi MPa 40 276
Elongation % in 2 in 30
Typical Hardness Ann Rockwell HRB80
Modulus of Elasticity Mpsi KMPa 30 207

Average Coefficient of Linear Expansion

Heat Treatment of the Samples   Average Coefficient of Linear Expansion
20~300℃ 20~400℃ 20~450°C
Heat to temperature of  900±20℃ in the hydrogen, hold for 1h; re-heat to 1100±20℃, hold for 15 min.; cooled to 200℃ at a rate less than 5℃/min   4.6 t o  5.2 5.1 to 5.5

Mean Coefficient of linear expansion at different temperature, ā/(10-6/K)

Kovar alloy parameter

Size Range

Sheet Thickness:0.10mm~3.50mm, width: ≤300mm
Plate Thickness:3.5mm~40.0mm, width: ≤500mm
Round wire Thickness:0.10mm~5.0mm
Flat Wire Dia 0.5mm~Dia 5.0mm, length≤1000
Rod Dia 5.0mm~Dia 8.0mm, length≤2000
Dia 8.0mm~Dia 32.0mm, length≤2500
Dia 32.0mm~Dia180.0mm, length≤1000
Capillary OD 8.0mm~1.0mm,ID 0.1~8.0 length≤2500
Pipe OD 120mm~8.0mm,ID 8.0~129 length≤4000

Condition: (With max tolerance) cold rolled, cold drawn, hot rolled , hot forging ,peeled turned ,bright ,bright annealed

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