Expansion alloy

Expansion alloy (constant expansion alloy) is a type of functional metal material with controlled thermal expansion characteristics. This type of material is widely used in areas where thermal expansion needs to match that of other materials such as glass and ceramics, or where a high degree of dimensional stability is required over a specific temperature range. The products we offer have excellent physical properties and long-term stability.

4J29 Kovar

4J29 (Kovar) has a thermal expansion coefficient similar to that of hard glass and ceramics, making it an ideal material for manufacturing hermetic sealing components. It has good processing performance and excellent sealing strength.

Expansion Kovar

4J29

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✓ Established in 2002
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Features

4J29 alloy has a matching coefficient of thermal expansion with glass and ceramics, making it suitable for airtight sealing applications.

Applications

Electron tube casings
Integrated circuit lead frames
Vacuum devices

Specifications

Plate / Sheet
Thickness: 0.1mm-20mm
Width: 50mm-1000mm
Length: 1000mm-6000mm
Strip
Thickness: 0.02mm-1mm
Width: 3mm-500mm
Delivery Forms: Bright shiny surface or anodized surface, supplied in spools or cut-to-length
Rod
Diameter: Ø3mm-Ø100mm
Length: 100mm-2000mm
Delivery Forms: Hot rolled, forged or turned
Wire
Diameter: Ø0.03mm-Ø6mm
Delivery Forms: Bright shiny or anodized, supplied in spools
Tube
Outer Diameter: Ø3mm-Ø200mm
Wall Thickness: 0.5mm-10mm
Length: 100mm-6000mm

Chemical Composition

Elements		4J29
Carbon (C)	Not greater than	0.03
Sulfur (S)		0.02
Phosphorus (P)		0.02
Manganese (Mn)		≤0.50
Silicon (Si)		≤0.30
Nickel (Ni)		28.5-29.5
Cobalt (Co)		16.8-17.8
Iron (Fe)		Rest

Thermal Expansion Properties

Alloy Grade	20°C-100°C	20°C-300°C	20°C-500°C
4J29 Kovar Alloy	4.6×10⁻⁶ /°C	5.5×10⁻⁶ /°C	6.2×10⁻⁶ /°C

Mechanical Properties

Alloy Grade	4J29 Kovar Alloy
Density (g/cm³)	8.2
Tensile Strength (MPa)	600-700
Yield Strength (MPa)	300-400
Hardness (HV)	200-250

Electrical Properties

Alloy Grade	4J29 Kovar Alloy
Electrical Resistivity (10⁻⁶ Ω·cm)	50
Thermal Conductivity (W/m·K)	16-18

Supply Capability

Item	Details
Lead Time	Samples 5-10 days; production 15-30 days
MOQ	Small trial orders accepted
Samples	Available on request
Packaging	Export-standard coil spools / wooden cases
Certificate	COC with chemical composition analysis
Payment	T/T, L/C

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Frequently Asked Questions (FAQ)

What is the chemical composition of 4J29 (29НК) Kovar alloy?

Nickel 28.5-29.5%, cobalt 16.8-17.8%, iron balance, manganese ≤ 0.50%, silicon ≤ 0.30%, carbon ≤ 0.03%, sulfur and phosphorus ≤ 0.02% each. The cobalt-nickel combination makes the expansion curve match that of hard glass and ceramics, achieving reliable hermetic sealing. It is a classic material for electronic sealing.

What is the linear expansion coefficient of 4J29?

What are the mechanical and physical parameters of 4J29?

What products is 4J29 mainly used for?

It is used for airtight sealing components such as electron tube shells and electrode sealing, integrated circuit lead frames, vacuum devices and sensor housings. It relies on the expansion coefficient matching that of glass ceramics to ensure sealing strength and airtightness, and has good processing and welding performance. It is available in plates, rods, and wire tubes.

What specifications are available for 4J29 Kovar alloy?

Plate thickness 0.1-20mm, width 50-1000mm; strip/foil thickness 0.02-1mm, width 3-500mm; rod diameter 3-100mm; wire diameter 0.03-6mm; pipe outer diameter 3-200mm, wall thickness 0.5-10mm, cold rolled bright or annealed delivery.