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

• Product Type: Wire
• Material: Feni
• Carbon Content: Low Carbon
• PCD: -
• ET: -
• Hole: -
• Transport Package: Plastic Shaft, Roll Bag, Drum
• Specification: Wire Diameter Range: 0.05mm-8mm
• Trademark: OHMALLOY
• Origin: China(Shanghai)
• HS Code: 7202999000
• Production Capacity: 50 Tons Per Month

Product Description

OhmAlloy-4J29 (Expansion alloy)
(Common Name: Kovar, Nilo K, KV-1, Dilver P_o, Vacon 12)
OhmAlloy-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.
OhmAlloy-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(Ωmm^2/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

 
Style of supply

Alloys Name	Type	Dimension
OhmAlloy-4J29	Wire	D= 0.1~8mm
OhmAlloy-4J29	Strip	W= 5~250mm	T= 0.1mm
OhmAlloy-4J29	Foil	W= 10~100mm	T= 0.01~0.1
OhmAlloy-4J29	Bar	Dia= 8~100mm	L= 50~1000