|Standard:||DIN,JIS,ASTM||Composition:||Nickel Cobalt, Ferro|
|Use:||Chemical Industry||Ni:||Min 28.5%|
Bright Shiny Kovar Foil Wear Resistant Astm F15 / Uns K94610 With Weldability
4J29, is a nickel-cobalt ferrous alloy compositionally identical to Fernico 1, designed to have substantially the same thermal expansion characteristics as borosilicate glass (~5 × 10−6 /K between 30 and 200 °C, to ~10 × 10−6 /K at 800 °C) in order to allow a tight mechanical joint between the two materials over a range of temperatures. Corresponding to GB 4J29, ASTM F15, UNS K94610); KOVAR is a hard glass iron-based seal bond containing 29% nickel and 17% cobalt. It finds application in glass-to-metal seals in scientific apparatus, and conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs.
Kovar was invented to meet the need for a reliable glass-to-metal seal, which is required in electronic devices such as light bulbs, vaccum tubes, cathode ray tubes, and in vacuum systems in chemistry and other scientific research. The alloy has a coefficient of linear expansion similar to that of hard glass in the range of 20-450 ° C, which can be effectively sealed with the corresponding hard glass, and has a high Curie point and good low temperature structure stability, oxidation of the alloy. The film is dense, easy to weld and weld, has good plasticity, and can be cut and processed. It is widely used in the manufacture of electric vacuum components, launch tubes, picture tubes, switch tubes, transistors, sealed plugs and relay housings. Kovar alloy is more wear-resistant because of its cobalt content. 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.
Because of its effect on the actual structure of the material, there is a distinction made between heat treating the material to facilitate fabrication and heat treating the material to ensure optimum conditions for glass sealing, plating or brazing.
Stress Relief Annealing
To relieve stress and work hardening of parts at intermediate stages of fabrication. It is intended particularly for drawing, forming and spinning operations.
1. Wash and degrease parts.
2. Anneal in atmosphere controlled furnace. Atmosphere may be wet or dry hydrogen, dissociated ammonia, cracked gas or similar neutral atmosphere.
3. Annealing temperature is not critical; however, high temperatures (greater than 900 oC) or extended time periods (longer than 60 minutes) should be avoided because such treatments promote grain growth.
Typical cycle: 850 oC for 30 minutes.
4. Parts should be held at temperature for the indicated time and then furnace cooled to less than 175 oC to avoid oxidation and/or thermal shock (which may cause distortion).
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