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Kovar Precision Alloy tube Description
Kovar Tube is a nominal 29%NiCoFe alloy that is a well-known
glass-sealing alloy suitable for sealing to hard glasses.
(Common Name: Kovar, NiFeCo29, NiCoFe294,Nilo K)
Kovar Precision Alloy tube Chemical Domposition
| alloy | C | Mn | Si | P | S | Ni | Cr | Co | Cu | Mo | Fe |
| 4J29 | ≤0.03 | ≤0.50 | ≤0.30 | ≤0.020 | ≤0.020 | 28.5~29.5 | ≤0.20 | 16.8~17.8 | ≤0.2 | ≤0.2 | balance
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| Controlled Expansion and Glass Sealing Alloys | |||
| German standard number | Tradename | DIN | UNS |
| 1.2937 | Alloy 29 | 17745 | K92900 |
| 1.3917 | Alloy 42 | 17745 | K94100 |
| 1.3922 | Alloy 48 | 17745 | K94800 |
| 1.3981 | Pernifer2918 | 17745 | K94610 |
| 2.4478 | NiFe 47 | 17745 | N14052 |
| 2.4486 | NiFe47Cr | 17745 | - |
| Density (g/cm3) | 8.2 |
| Electrical resistivity at 20ºC(OMmm2/m) | 0.48 |
| Temperature factor of resistivity(20ºC~100ºC)X10-5/ºC | 3.7~3.9 |
| Curie point Tc/ ºC | 430 |
| Elastic Modulus, E/ Gpa | 138 |
| Code of condition | Condition | Wire | Strip |
| R | Soft | ≤585 | ≤570 |
| 1/4I | 1/4 Hard | 585~725 | 520~630 |
| 1/2I | 1/2 Hard | 655~795 | 590~700 |
| 3/4I | 3/4 Hard | 725~860 | 600~770 |
| I | Hard | ≥850 | ≥700 |
The heat treatment process
| Annealing for stress relief | Heated to 470~540ºC and hold 1~2 h. Cold down |
| annealing | In vacuum heated to 750~900ºC |
| Holding time | 14 min~1h. |
| Cooling rate | No more than 10 ºC/min cooled to 200 ºC |
Coefficient of expansion
| θ/ºC | α1/10-6ºC-1 | θ/ºC | α1/10-6ºC-1 |
| 20~60 | 7.8 | 20~500 | 6.2 |
| 20~100 | 6.4 | 20~550 | 7.1 |
| 20~200 | 5.9 | 20~600 | 7.8 |
| 20~300 | 5.3 | 20~700 | 9.2 |
| 20~400 | 5.1 | 20~800 | 10.2 |
| 20~450 | 5.3 | 20~900 | 11.4 |
