4J28 Rod / Bar | Kovar Alloy Rods for Glass-to-Metal Sealing Applications
Product Description
4J28 alloy rod is an iron-nickel-cobalt (Fe-Ni-Co) controlled expansion alloy specially designed for glass-to-metal and ceramic-to-metal sealing applications. It has a linear expansion coefficient that precisely matches hard glass and ceramics, ensuring reliable hermetic sealing.
With stable mechanical strength, excellent machinability, and outstanding sealing performance, 4J28 rods are widely used in electronic packaging, vacuum devices, semiconductor components, and aerospace instruments.
Key Features
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Fe-Ni-Co alloy with controlled thermal expansion
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Excellent sealing performance with glass and ceramics
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Stable mechanical strength at various temperatures
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Easy machining and surface treatment
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Reliable long-term hermeticity
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Available in rods, wires, sheets, and customized forms
Typical Applications
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Glass-to-metal hermetic sealing
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Electronic packaging components
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Vacuum tubes and light bulbs
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Semiconductor packaging bases
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Aerospace and defense devices
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Sensor housings and feedthroughs
Chemical Composition (%)
| Element | Content |
|---|---|
| Fe | Balance |
| Ni | ~28% |
| Co | ~18% |
| Minor Elements | Mn, Si, C, etc. |
Physical and Performance Properties
| Property | Typical Value |
|---|---|
| Density | ~8.2 g/cm³ |
| Thermal Expansion (20–400°C) | ~5.0 ×10⁻⁶/°C |
| Tensile Strength | ≥ 450 MPa |
| Hardness | ~HB 140–170 |
| Working Temp | -196°C to 450°C |
| Standard | GB/T, ASTM, IEC |
Available Specifications
| Item | Range |
|---|---|
| Diameter | 3 mm – 200 mm |
| Length | ≤ 6000 mm |
| Tolerance | As per ASTM / GB standard |
| Surface | Bright / Polished / Black |
| Packaging | Wooden case, steel strip bundling |
| Certification | ISO 9001, SGS, RoHS |
| Origin | China (OEM/ODM service available) |
Packaging & Shipping:
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Packaging:
Plastic spools, vacuum bags, anti-rust wrapping, and customized labels upon request -
Shipping Methods:
Air freight, sea freight, express delivery -
Lead Time:
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7–15 working days based on order quantity
Get in Touch
Have questions about our products or want to discuss a custom order? Our team is ready to help you.