4J29 Rod Kovar Alloy Bar Fe Ni Co Controlled Expansion Alloy for Glass to Metal Sealing
Product Description
4J29 alloy rod, also known as Kovar rod, is a Fe-Ni-Co controlled expansion alloy with a thermal expansion coefficient closely matching that of hard glass and ceramics. It provides excellent glass-to-metal and ceramic-to-metal sealing properties, ensuring reliable hermeticity.
With stable mechanical performance, good machinability, and outstanding sealing reliability, 4J29 rods are widely applied in electronic packaging, vacuum devices, semiconductor bases, sensors, and aerospace instruments.
Key Features
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Fe-Ni-Co controlled expansion alloy
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Thermal expansion matches hard glass and ceramics
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Excellent hermetic sealing performance
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Stable mechanical strength at different temperatures
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High machinability and surface finish
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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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Semiconductor packaging bases
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Electronic packaging components
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Vacuum tubes and light bulbs
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Aerospace and defense devices
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Sensors, relays, and feedthroughs
Chemical Composition (%)
| Element | Content |
|---|---|
| Fe | Balance |
| Ni | ~29% |
| Co | ~17% |
| 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.