Expansion Alloys
Precision Sealing · Controlled Expansion · 4J29 / 4J36 / 4J42 / 4J43 · Strip, Wire, Bar, Tube
High-Performance Expansion Alloys Solutions
Executive standards: YB/T 5231-2005, YB/T 5241-2005, YB/T 5235-2005, etc.
Expansion alloys fall into low-expansion alloys and controlled-expansion alloys, the latter also known as sealing alloys. Beyond a specific coefficient of thermal expansion, these alloys must offer—depending on the application—good sealing capability, weldability, corrosion resistance, machinability and free-cutting properties, with no phase transformation within the service temperature range that would noticeably alter their expansion characteristics.
Products are generally supplied as bar, sheet, strip, wire and tube, and are widely used for glass-, metal- and ceramic-to-metal sealing in aerospace electrical equipment and instruments, the vacuum electronics industry and other electronic devices, as well as electric light sources.
Why Choose Kunsen Expansion Alloys
Precise Matching, Reliable Sealing
Alloys with precisely controlled thermal expansion ensure perfectly matched seals, greatly improving the hermeticity, reliability and service life of your components.
Thermal Control Expertise
Enabling equipment to respond intelligently to temperature changes—suppressing deformation and eliminating stress—as a core material for thermal management in high-end instruments.
Indispensable Applications
Vacuum Electronic Devices
Hermetic glass-to-metal and ceramic-to-metal seals in the vacuum electronics industry.
Aerospace Instruments
Thermally matched components for aerospace electrical equipment and precision instruments.
Electric Light Sources
Sealing and support structure materials for electric light source applications.
Specifications & Grades
Chemical Composition(mass fraction, %)
| Grade | C | S | P | Mn | Si | Ni | Cr | Co | Cu | Mo | Se | Al | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 4J43 | 0.20 | 0.02 | 0.02 | 0.75-1.25 | ≤0.30 | 41.0-43.0 | – | – | – | – | – | – | Bal. |
| 4J29 | 0.03 | 0.02 | 0.02 | ≤0.50 | ≤0.30 | 28.5-29.5 | ≤0.2 | 16.8-17.8 | ≤0.2 | ≤0.2 | – | – | Bal. |
| 4J36 | 0.05 | 0.02 | 0.02 | 0.20-0.60 | ≤0.30 | 35.0-37.0 | – | – | – | – | – | – | Bal. |
| 4J42 | 0.05 | 0.02 | 0.02 | ≤0.80 | ≤0.30 | 41.5-42.5 | – | ≤0.1 | – | – | – | ≤0.1 | Bal. |
Executive standards: GB/T 15018-1994, YB/T 5231-2005, YB/T 5235-2005, etc. C, S and P values are maximum limits.
Need Expansion Alloys selection advice or a quote?
Our technical team provides material selection advice and engineering support to ensure optimal performance in your application.