Precision Alloys
Kovar / 4J29 (UNS K94610) — Composition, Properties & Supply
4J29 (Kovar, UNS K94610) is an iron-nickel-cobalt controlled-expansion sealing alloy. With a CTE of about 4.6–5.2×10⁻⁶/°C from 20 to 450 °C it matches borosilicate glass and alumina ceramic, making it the standard for vacuum tubes, semiconductor packaging and hermetic seals.
What is the chemical composition of Kovar / 4J29?
| Element | Symbol | Content (wt%) |
|---|---|---|
| Fe | Fe | Balance |
| Ni | Ni | 28.5–29.5 |
| Co | Co | 16.8–17.8 |
| Mn | Mn | ≤ 0.50 |
| Si | Si | ≤ 0.30 |
| C | C | ≤ 0.03 |
| P | P | ≤ 0.020 |
| S | S | ≤ 0.020 |
Values are typical specification limits. Actual heat analysis is reported on the EN 10204 3.1 mill test certificate supplied with each shipment.
What are the mechanical properties of Kovar / 4J29?
| Property | Value | Note |
|---|---|---|
| Tensile strength | ≥ 520 MPa | Room temperature |
| Yield strength (0.2% offset) | ≥ 340 MPa | Room temperature |
| Elongation | ≥ 25 % | Gauge length 50 mm / 4D |
| Hardness | ≤ 190 HB | Brinell / Rockwell |
What are the physical properties of Kovar / 4J29?
| Property | Value |
|---|---|
| Density | 8.36 g/cm³ |
| Melting range | 1450–1470 °C |
| Thermal conductivity | 17.0 W/m·K |
| Elastic modulus | 138 GPa |
| Maximum service temperature | −80 ~ +450 ℃ |
What are the key characteristics of Kovar / 4J29?
- CTE precisely matched to borosilicate glass and alumina ceramic
- Highly reliable hermetic seals with long thermal-cycle life
- Good machinability plus plating and welding performance
- Forms a strong chemical bond with glass
Where is Kovar / 4J29 used?
- IC and power device packages
- Vacuum tubes, magnetrons and travelling-wave tubes
- Aerospace and military hermetic electronic packaging
- Sensor and relay housings
- Solar cell and laser device packaging
Which standards and specifications cover Kovar / 4J29?
- ASTM F15
- GB/T 14985
- UNS K94610
What product forms are available?
Frequently asked questions
What is the difference between 4J29 and 4J36?
4J36 (Invar) targets minimal expansion (about 1.2×10⁻⁶/°C) for dimensionally stable parts, while 4J29 (Kovar) targets a controlled expansion (about 5×10⁻⁶/°C) matched to glass and ceramic for hermetic sealing. 4J29 contains 17% cobalt and costs more; the two are not interchangeable.
Need Kovar / 4J29 bar, tube, plate or forgings?
Send the grade, dimensions, standard and quantity. We answer within 10 minutes on working days and quote within 24 hours, with EN 10204 3.1 certification.
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