China Low Expansion Alloy Kovar 4j29 Wire, 29HK Wire for Glass Sealing Alloy Manufacture and Factory

Low Expansion Alloy Kovar 4j29 Wire, 29HK Wire for Glass Sealing Alloy

Short Description:

Alloy-4J29 (Expansion alloy)
(Common Name: Kovar, Nilo K, KV-1, Dilver Po, Vacon 12)
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.

Model NO.: Kovar

OEM: Yes

State: Soft 1/2hard hard T-hard

HS Code: 74099000

Origin: China

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Alloy-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.

Application: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(Ωmm2/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

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

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