Glass sealing alloy kovar wire/bar/plate/sheet/tube/rod

Glass sealing alloy kovar wire/bar/plate/sheet/tube/rod

Short Description:

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

Product Detail

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4J29 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.

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 20℃(Ωmm2/m) 0.48
Temperature factor of resistivity(20℃~100℃)X10-5/℃ 3.7~3.9
Curie point   Tc/ ℃ 430
Elastic Modulus,  E/ Gpa 138

Coefficient of expansion

θ/℃ α1/10-6-1 θ/℃ α1/10-6-1
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/℃ 100 200 300 400 500
λ/ W/(m*℃) 20.6 21.5 22.7 23.7 25.4


The heat treatment process
Annealing for stress relief Heated to 470~540℃ and hold 1~2 h. Cold down
annealing In vacuum heated to 750~900℃
Holding time   14 min~1h.
Cooling rate No more than  10 ℃/min cooled to 200 ℃

Style of supply

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

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    Large size range from 0.025mm (.001”) to 21mm (0.827”)

    Order Quantity ranging from 1 kg to 10 tonnes
    At Cheng Yuan Alloy, we take great pride in customer satisfaction and frequently discuss individual requirements, offering a tailored solution through manufacturing flexibility and technical knowledge.

    Delivery within 3 weeks
    We typically manufacture your order and ship within 3 weeks, delivering our products to more than 55 countries across the world.

    Our lead times are short because we stock in excess of 200 tonnes of more than 60 ‘High Performance’ alloys and, if your finished product is not available from stock, we can manufacture within 3 weeks to your specification.

    We take pride in our more than 95% on time delivery performance, as we are always striving for excellent customer satisfaction.

    All wire, bars, strip, sheet or wire mesh are securely packed suitable for transporting by road, air courier or sea, with available in coils, spools and cut lengths. All items are clearly labelled with the order number, alloy, dimensions, weight, cast number and date.
    There is also the option to supply neutral packaging or labelling featuring the customer’s branding and company logo.

    Order is manufactured to your specification
    We produce wire, bar, flat wire, strip, sheet to your exact specification and in exactly the quantity you are looking for.
    With a range of 50 Exotic Alloys available, we can provide the ideal alloy wire with specialist properties best suited to your chosen application.
    Our alloy products, such as the corrosion resistant Inconel® 625 Alloy, is designed for aqueous and off-shore environments, while the Inconel® 718 alloy offers superior mechanical properties in low and sub-zero temperature environments. We also have high strength, hot cutting wire ideal for high temperatures and perfect for cutting polystyrene (EPS) and heat sealing (PP) food bags.
    Our knowledge of the industry sectors and state-of-the-art machinery means we can reliably manufacture alloys to strict design specifications and requirements from all over the world.

    Our ‘Emergency Manufacturing Service’ for delivery within days
    Our usual delivery times are 3 weeks, however if an urgent order is required, our Emergency Manufacturing Service ensures your order is manufactured within days and shipped to your door via the fastest route possible.

    If you have an emergency situation and require products even faster, contact us with your order specification. Our technical and production teams will swiftly respond to your quote.

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    The product forms include wire, flat wire, strip, plate, bar, foil, seamless tube , Wire mesh, powder, etc., can meet the application needs of different customers.

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