4J29 / Kovar Alloy Tube | Fe-Ni-Co Controlled Expansion Alloy
Product Overview
4J29 tubing (Kovar tube) is an iron–nickel–cobalt controlled-expansion alloy widely used for hermetic sealing, electronic packaging, and glass-to-metal or ceramic-to-metal joints.
Its thermal expansion closely matches borosilicate glass and alumina ceramics, ensuring excellent sealing performance and long-term dimensional stability.
The material features high strength, excellent air-tightness, and stable thermal properties, making it ideal for high-reliability applications in aerospace, electronics, sensors, medical devices, and vacuum components.
Key Features
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Controlled Thermal Expansion: Matches the expansion of borosilicate glass and 95%–99% alumina ceramics.
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Excellent Hermeticity: Ensures tight, leak-free glass-to-metal and ceramic-to-metal seals.
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High Strength & Stability: Maintains mechanical performance under thermal cycling and long-term service.
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Good Machinability & Formability: Suitable for drawing, deep processing, precision machining, and welding.
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Reliable in High-Vacuum Environments: Low outgassing and excellent structural stability.
Main Applications
| Industry | Typical Application | Description / Purpose |
|---|---|---|
| Electronics | Vacuum tubes, transistor housings, IC packages | Hermetic glass-to-metal sealing |
| Aerospace | Sensor housings, feedthroughs | High-reliability expansion-matched components |
| Medical Devices | Laser housings, X-ray components | Stable sealing in vacuum/sterile environments |
| Optical & Laser | Laser tubes, photodiode housings | Dimensional stability under thermal load |
| Instrumentation | Precision connectors, relays | For controlled-expansion components |
Chemical Composition (Typical, %)
| Element | Ni | Co | Fe | Mn | Si | C | P | S |
|---|---|---|---|---|---|---|---|---|
| Content | 28.5–29.5 | 16.5–17.5 | Balance | ≤ 0.3 | ≤ 0.3 | ≤ 0.02 | ≤ 0.02 | ≤ 0.02 |
Complies with ASTM F15 / GB 4J29 / UNS K94610.
Technical Specifications
| Item | Value |
|---|---|
| Material Type | Fe-Ni-Co Controlled Expansion Alloy |
| Standard | ASTM F15 / GB 4J29 |
| Density | 8.2 g/cm³ |
| Tube OD Range | 0.3 mm – 60 mm (custom available) |
| Wall Thickness | 0.05 mm – 5 mm |
| Melting Range | 1450 – 1500 °C |
| Thermal Expansion (20–300°C) | 4.6 × 10⁻⁶ /K |
| Condition | Annealed / Bright Annealed / Cold Drawn |
| Surface | Bright / Clean / Oxide-Free |
| Form | Tube / Capillary Tube / Precision Cut Length |
Supply Capability
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Regular Stock: ≥ 8 tons/month
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Lead Time: 7 – 12 working days
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OEM / ODM: Available (cut-to-length, machining, custom dimensions)
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Export Regions: Europe | Southeast Asia | Middle East | North America
Custom Attributes
| Attribute | Value |
|---|---|
| Grade | 4J29 / Kovar / ASTM F15 |
| Color | Metallic Silver |
| Tensile Strength | ≥ 450 MPa |
| Hardness | 130–180 HV (Annealed) |
| Application Field | Electronics / Aerospace / Medical / Laser |
| Tube Type | Seamless Tube / Capillary Tube |
| Packaging | Wooden case / Carton / Vacuum packing |
Get in Touch
Have questions about our products or want to discuss a custom order? Our team is ready to help you.