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Expansion Precision Alloy 4J29 (Ni29Co18) UNS K94610 Electric Vacuum Kovar Strip Tube Bar Wire Plate
OhmAlloy-4J29 (Expansion alloy)
(Common Name: Kovar, Nilo K, KV-1, Dilver Po, Vacon 12)
OhmAlloy-4J29 also known as Kovar alloy. it was invented to meet the need for a reliable glass-to-metal seal, which is required in electronic devices such as light bulbs, vacuum tubes, cathode ray tubes, and in vacuum systems in chemistry and other scientific research. Most metals cannot seal to glass because their coefficient of thermal expansion is not the same as glass, so as the joint cools after fabrication the stresses due to the differential expansion rates of the glass and metal cause the joint to crack.
Chemical Composition
| Grade | C% | P% | S% | Mn% | Si% | Cu% | Cr% | Mo% | Ni% | Co% | Fe% |
| Kovar | Max 0.03 | Max 0.020 | Max 0.020 | Max 0.50 | Max 0.30 | Max 0.20 | Max 0.20 | Max 0.20 | 28.5-29.5 | 16.8-17.8 | Bal. |
Specifications
| Grade | UNS | Werkstoff Nr. |
| Kovar | K94610 | 1.3981 |
Physical Properties
| Grade | Density | Melting Point |
| Kovar | 8.17 g/cm3 | 1449°C |
Mechanical Properties
| Grade | Tensile Strength N/mm² | ||||
| Soft | 1/4 Hard | 1/2 Hard | 3/4 Hard | Full Hard | |
| Kovar Strip | <570 | 520-630 | 590-700 | 600-770 | >700 |
| Kovar Wire | <585 | 585-725 | 655-795 | 725-860 | >860 |
Coefficient of Expansion
| Alloy | Linear Coefficient of Thermal Expansion a,10-6/°C | |||||||
| 20-200°C | 20-300°C | 20-400°C | 20-450°C | 20-500°C | 20-600°C | 20-700°C | 20-800°C | |
| Kovar | 5.9 | 5.3 | 5.1 | 5.3 | 6.2 | 7.8 | 9.2 | 10.2 |
Package