TANKII ALLOY
sealing glass elements of vacuum Relays
TANKII Alloy-4J29 (Expansion alloy)
(Common Name: Kovar, Nilo K, KV-1, Dilver Po, Vacon 12)
TANKII ALLOY-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.
Kovar is a nickel-cobalt ferrous alloy compositionally identical to
Fernico, designed to be compatible with the thermal expansion
characteristics of borosilicate glass (~5 × 10−6 /K between 30 and
200 °C, to ~10 × 10−6 /K at 800 °C) in order to allow direct
mechanical connections over a range of temperatures. It finds
application in electroplated conductors entering glass envelopes of
electronic parts such as vacuum tubes (valves), X-ray and microwave
tubes and some lightbulbs.
The name Kovar is often used as a general term for Fe-Ni alloys
with these particular thermal expansion properties. Note the
related particular Fe-Ni alloy Invar which exhibits minimum thermal
expansion.
TANKII ALLOY-4J29was 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.
TANKII ALLLOY-4J29 not only has thermal expansion similar to glass,
but its nonlinear thermal expansion curve can often be made to
match a glass, thus allowing the joint to tolerate a wide
temperature range. Chemically, it bonds to glass via the
intermediate oxide layer of nickel oxide and cobalt oxide; the
proportion of iron oxide is low due to its reduction with cobalt.
The bond strength is highly dependent on the oxide layer thickness
and character. The presence of cobalt makes the oxide layer easier
to melt and dissolve in the molten glass. A grey, grey-blue or
grey-brown color indicates a good seal. A metallic color indicates
lack of oxide, while black color indicates overly oxidized metal,
in both cases leading to a weak joint.
Mainly used in electric vacuum components and emission control,
shock tube, igniting tube, glass magnetron, transistors, seal plug,
relay, integrated circuits lead, chassis, brackets and other
housing sealing.
Normal composition%
| Ni | 28.5~29.5 | Fe | Bal. | Co | 16.8~17.8 | Si | ≤0.3 |
| Mo | ≤0.2 | Cu | ≤0.2 | Cr | ≤0.2 | Mn | ≤0.5 |
| C | ≤0.03 | P | ≤0.02 | S | ≤0.02 | | |
Tensile Strength, MPa
| 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 |
Typical Physical properties
| 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 |
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 |
Thermal conductivity
| θ/ºC | 100 | 200 | 300 | 400 | 500 |
| λ/ W/(m*ºC) | 20.6 | 21.5 | 22.7 | 23.7 | 25.4 |
Style of supply
| Alloys Name | Type | Dimension | |
| 4J29 | Wire | D= 0.1~8mm | |
| 4J29 | Strip | W= 5~250mm | T= 0.1mm |
| 4J29 | Foil | W= 10~100mm | T= 0.01~0.1mm |
| 4J29 | Bar | Dia= 8~100mm | L= 50~1000mm |
1. What's the minimum quantity customer can order?
If we have your size in stock, we can provide any quantity you
want.
If we do not have, for spool wire, we can produce 1 spool, about
2-3kg. For coil wire, 25kg.
2. How can you pay for small sample amount?
We have Western union account, wire transfer for sample amount also
ok.
3. Customer do not have express account. How will us arrange the
delivery for sample order?
Just need to provide your address information, we will check the
express cost, you can arrange the express cost together with sample
value.
4. What's our payment terms?
We can accept LC T/T payment terms, it also depending on delivery
and total amount. Let's talk more in details after getting your
detailed requirements.
5. Do you provide free samples?
If you want several meters and we have stock of your size, we can
provide, customer need to bear the International express cost.
6. What's our working time?
We will give you reply through email/phone Online contact tool
within 24 hours. No matter working day or holidays.
