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Kovar Controlled Expansion Alloy ASTM F-15 UNS K94610 Glass Sealing Alloy
Kovar controlled expansion alloy, most likely know as 4J29 in China, is a Nickel Iron alloy with 29% Nickel, 17% Cobalt and the remaining balance is Iron.
Kovar controlled expansion alloy, 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 area.
Kovar has thermal expansion similar to glass. Meanwhile its nonlinear thermal expansion curve can often be made to match a glass. This makes it the most popular controlled expansion alloy so far.
Chemical compostion of Kovar
| Alloy | % | Ni | Cr | Co | Cu | C | Mn | Si | P | S | Mo | Fe |
| Kovar | Min | 28.5 | 16.8 | Rem | ||||||||
| Max | 29.5 | 0.2 | 17.8 | 0.20 | 0.03 | 0.50 | 0.30 | 0.02 | 0.02 | 0.20 |
The average linear expansion coefficient(10-6C)
| 20~100°C | 20~300°C | 20~400°C | 20~450°C | 20~500°C | 20~530°C | 20~600°C |
| — | — | 4.6~5.2 | 5.1~5.5 | — | — | — |
Applications of Kovar
Forms available at A-ONE ALLOY