4J33 alloy wire, often known as an Fe-Ni-Co (Iron-Nickel-Cobalt) alloy, is a precision-controlled expansion material designed for reliable glass-to-metal sealing applications. It contains approximately 33% nickel, 17% cobalt, and the balance iron. This composition gives 4J33 wire a carefully tuned coefficient of thermal expansion (CTE) that matches the expansion of certain types of hard glass, such as borosilicate.
At DLX, we specialize in manufacturing high-purity 4J33 alloy wire with consistent microstructure and excellent bonding performance. Our production line ensures precise control of composition, micro-cleanliness, and dimensional accuracy — the key factors in achieving perfect hermetic sealing between metal and glass.
For more details, pls directly contact us.
The global demand for hermetic sealing materials is growing with the expansion of advanced electronics, aerospace systems, and semiconductor packaging. As microelectronics become smaller and more powerful, the need for highly reliable glass-to-metal seals increases — especially for components exposed to harsh conditions such as radiation, vibration, or extreme temperatures.
The Fe-Ni-Co system, particularly 4J33, has become a standard in high-reliability sealing due to its near-perfect CTE match with borosilicate glass. DLX’s precision manufacturing and strict quality management enable consistent sealing performance, meeting the evolving needs of next-generation electronic and aerospace industries.
In addition, with the growing emphasis on energy-efficient and long-life materials, 4J33’s corrosion resistance and thermal stability make it an environmentally responsible choice, reducing waste and maintenance requirements over product lifespans.
| Elements | 4J29 | 4J36 | |
| Carbon (C) | Not greater than | 0.03 | 0.05 |
| Sulfur (S) | 0.02 | 0.02 | |
| Phosphorus (P) | 0.02 | 0.02 | |
| Manganese (Mn) | ≤0.50 | 0.20-0.60 | |
| Silicon (Si) | ≤0.30 | ≤0.30 | |
| Nickel (Ni) | 28.5-29.5 | 35.0-37.0 | |
| Chromium (Cr) | - | - | |
| Cobalt (Co) | 16.8-17.8 | - | |
| Iron (Fe) | Rest | Rest | |
| Other Elements |
| Alloy Grade | 20°C-100°C | 20°C-300°C | 20°C-500°C |
| 4J36 Invar Alloy | 1.2×10⁻⁶ /°C | 2.5×10⁻⁶ /°C | - |
| 4J29 Kovar Alloy | 4.6×10⁻⁶ /°C | 5.5×10⁻⁶ /°C | 6.2×10⁻⁶ /°C |
| Alloy Grade | 4J36 Invar Alloy | 4J29 Kovar Alloy |
| Density (g/cm³) | 8.1 | 8.2 |
| Tensile Strength (MPa) | 500-600 | 600-700 |
| Yield Strength (MPa) | 250-350 | 300-400 |
| Hardness (HV) | 150-200 | 200-250 |
| Alloy Grade | 4J36 Invar Alloy | 4J29 Kovar Alloy |
| Electrical Resistivity (10⁻⁶ Ω·cm) | 80 | 50 |
| Thermal Conductivity (W/m·K) | 10-12 | 16-18 |
For more details, pls directly contact us.
The global demand for hermetic sealing materials is growing with the expansion of advanced electronics, aerospace systems, and semiconductor packaging. As microelectronics become smaller and more powerful, the need for highly reliable glass-to-metal seals increases — especially for components exposed to harsh conditions such as radiation, vibration, or extreme temperatures.
The Fe-Ni-Co system, particularly 4J33, has become a standard in high-reliability sealing due to its near-perfect CTE match with borosilicate glass. DLX’s precision manufacturing and strict quality management enable consistent sealing performance, meeting the evolving needs of next-generation electronic and aerospace industries.
In addition, with the growing emphasis on energy-efficient and long-life materials, 4J33’s corrosion resistance and thermal stability make it an environmentally responsible choice, reducing waste and maintenance requirements over product lifespans.
Material Composition and Key Properties
| Parameter | 4J33 (Fe-Ni-Co Alloy) | 4J36 (Invar 36) | Kovar-Type Alloy |
|---|---|---|---|
| Nickel (Ni) | 33% ± 1% | 36% ± 1% | 29% ± 1% |
| Cobalt (Co) | 17% ± 1% | — | 17% ± 1% |
| Iron (Fe) | Balance | Balance | Balance |
| Density (g/cm³) | 8.2 | 8.1 | 8.4 |
| Coefficient of Expansion (20–450°C) | 5.2 × 10⁻⁶ /°C | 1.2 × 10⁻⁶ /°C | 5.0 × 10⁻⁶ /°C |
| Melting Point (°C) | 1430–1450 | 1425–1450 | 1430–1450 |
| Tensile Strength (MPa) | 520–650 | 450–550 | 500–700 |
| Resistivity (μΩ·m) | 0.47 | 0.78 | 0.48 |
| Magnetic Properties | Magnetic | Weakly magnetic | Magnetic |
This alloy’s key advantage lies in its controlled expansion behavior that precisely matches glass materials, ensuring a durable and airtight bond under thermal cycling and mechanical stress.
Applications
1. Glass-to-Metal Seals:
The primary application of 4J33 wire is in sealing glass to metal components used in vacuum tubes, sensors, electronic packaging, and feedthroughs. Its expansion compatibility prevents cracking or leakage under temperature variation.
2. Electronic and Semiconductor Devices:
4J33 is widely used for lead wires and connectors in electronic components requiring airtight hermetic seals. It provides excellent performance under heat, vacuum, and cryogenic conditions.
3. Aerospace Components:
Used in electronic packages, sensors, and connectors that experience frequent temperature changes, 4J33 ensures the structural integrity of sealed systems.
4. Precision Instruments:
It serves in optical systems, scientific devices, and communication components where exact sealing and electrical insulation are crucial.
5. Vacuum and Cryogenic Technology:
The alloy maintains stable properties even in deep vacuum and low-temperature environments, making it suitable for cryogenic feedthroughs and analytical instruments.
Why Choose DLX 4J33 Alloy Wire
DLX’s 4J33 alloy wire offers superior stability and reliability compared to typical Fe-Ni alloys, thanks to advanced refining and process control technologies. Our manufacturing focuses on high purity, smooth surface finish, and tight dimensional tolerances — essential for flawless sealing and long-term performance.
Key Advantages of DLX 4J33 Wire:
-
Perfect Expansion Matching:
Our 4J33 wire achieves precise thermal expansion alignment with borosilicate glass, ensuring crack-free, hermetic seals in demanding applications. -
Exceptional Purity:
Produced under vacuum melting and refined atmosphere protection, DLX alloy wires have ultra-low impurity levels, minimizing oxidation and improving bonding. -
Dimensional Precision:
Diameter control down to ±0.005mm guarantees stable sealing properties during automated assembly and high-speed production. -
Excellent Formability:
The wire can be easily drawn, wound, or welded without losing structural integrity, ideal for complex electronic sealing parts. -
Custom Solutions:
DLX provides tailored compositions, tempers, and spool sizes to match specific sealing glass and assembly processes.
Market Comparison
Many suppliers can provide standard Fe-Ni-Co wire, but DLX differentiates itself through consistency, technical precision, and long-term reliability. Our continuous production control and full traceability ensure that every spool of 4J33 wire maintains uniform metallurgical structure and expansion properties.
This performance consistency directly benefits manufacturers of vacuum tubes, sensors, and semiconductor components, as it reduces production defects and long-term failure rates. DLX also offers technical support for seal design and process optimization, ensuring customers achieve the best results from our materials.
Typical Specifications (Available from DLX)
| Property | DLX 4J33 Alloy Wire Specification |
|---|---|
| Diameter Range | 0.05 mm – 5 mm |
| Tensile Strength | 520–650 MPa |
| CTE (20–450°C) | (5.0–5.5) × 10⁻⁶ /°C |
| Resistivity | 0.47 μΩ·m |
| Density | 8.2 g/cm³ |
| Surface Finish | Bright / Oxide-Free |
| Delivery Condition | Annealed / Cold Drawn |
| Forms Available | Coil, Straight Wire, Spool |
DLX’s Commitment to Innovation
DLX continues to lead in precision alloy development through constant innovation in metallurgy, testing, and production automation. Our goal is not just to supply materials, but to provide engineering solutions for precision sealing, high-reliability electronics, and aerospace applications.
As electronic devices advance into smaller, faster, and more extreme environments, DLX’s materials ensure that every connection — from sensor feedthrough to vacuum packaging — performs flawlessly under stress. With strict quality assurance and responsive customer service, we deliver consistent performance that manufacturers worldwide can depend on.
About Us:
Our 12,000㎡ factory is equipped with complete capabilities for research, production, testing, and packaging. We strictly adhere to ISO 9001 standards in our production processes, with an annual output of 1,200 tons. This ensures that we meet both quantity and quality demands. Furthermore, all products undergo rigorous simulated environment testing including high temperature, high pressure, and corrosion tests before being dispatched, ensuring they meet customer specifications.
For all our clients, we offer timely and multilingual after-sales support and technical consulting, helping you resolve any issues swiftly and efficiently.
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FAQs
1. What is 4J33 alloy wire made of?
It’s composed of approximately 33% nickel, 17% cobalt, and the balance iron, forming a stable Fe-Ni-Co alloy for controlled thermal expansion.
2. Why is 4J33 used for glass-to-metal seals?
Its thermal expansion coefficient closely matches that of borosilicate glass, allowing stress-free, hermetic sealing during temperature cycles.
3. What is the typical working temperature range for 4J33 wire?
It performs reliably between -200°C and +450°C without significant expansion mismatch or oxidation.
4. Can DLX provide customized wire diameters?
Yes. DLX offers precision manufacturing from 0.05mm to 5mm with custom spools, tempers, and surface finishes.
5. Is 4J33 alloy magnetic?
Yes, it is magnetic at room temperature, which is beneficial for some sensor and electromagnetic applications.
6. How does DLX ensure consistent thermal expansion?
We control composition through vacuum melting and test each batch for CTE uniformity across multiple temperature points.
7. What kind of glass does DLX 4J33 wire seal with best?
It is ideal for borosilicate and hard glass types commonly used in vacuum and electronic sealing applications.
8. Does DLX export globally?
Absolutely. DLX supplies 4J33 wire to international aerospace, semiconductor, and precision instrument manufacturers worldwide.
