Description
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.
Application
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.
Product Parameter
Chemical Composition
| 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 | ||
| 20~300ºC | 20~400ºC | 20~450°C | |
| Heat to temperature of 900±20ºC in the hydrogen, hold for 1h; re-heat to 1100±20ºC, hold for 15 min.; cooled to 200ºC at a rate less than 5ºC/min | 4.6 t o 5.2 | 5.1 to 5.5 | |
