Invar 36 (4J36) Wire for Precision Instruments and Optical Devices

Invar 36, also known as 4J36 wire, is one of the most well-known controlled Expansion Alloy s in the world. It is a nickel-iron alloy that offers an exceptionally low coefficient of thermal expansion, making it perfect for applications that require high dimensional stability under temperature fluctuations. This unique property has made Invar 36 indispensable in precision instruments, optical devices, aerospace systems, and cryogenic engineering.

At DLX, we produce high-grade Invar 36 wire that meets the stringent demands of advanced industries. Through advanced melting and refining techniques, our 4J36 wire maintains outstanding chemical uniformity, mechanical strength, and surface precision—ensuring long-term performance and reliability across complex engineering applications.

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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

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• Ultra-low thermal expansion coefficient (≈ 1.3 × 10⁻⁶ /°C between −50°C and +200°C)

• Excellent dimensional stability across wide temperature ranges

• Strong mechanical strength with good ductility

• Superior corrosion resistance in neutral environments

• Compatible with glass and composite sealing systems

• Excellent machining, welding, and polishing properties

Typical Applications

Invar 36 (4J36) wire is widely used in industries that require temperature stability, precision, and mechanical integrity.

• Precision instruments – for components requiring dimensional accuracy under thermal variations.

• Optical devices – ideal for lens frames, support structures, and laser alignment systems.

• Aerospace – used in sensors, avionics, and structural components exposed to extreme temperature changes.

• Cryogenic systems – suitable for low-temperature devices and vacuum-insulated applications.

• Telecommunications and electronics – for relay elements and electronic control systems.

• Measurement and metrology equipment – ensures consistent accuracy in laboratory instruments.

Industry Analysis

Invar 36 has been the benchmark alloy for dimensional stability since its discovery, but modern technology has made it more valuable than ever. With the rapid development of aerospace, optics, and microelectronics, the need for materials that remain dimensionally stable across temperature shifts continues to rise.

In sectors like semiconductor lithography, satellite optics, and precision metrology, even a minor thermal expansion can cause errors worth millions. Invar 36 solves this by maintaining near-zero thermal growth, ensuring perfect alignment and calibration.

At DLX, we’ve observed a growing demand for ultra-pure, precision-drawn Invar wires across Europe, North America, and Asia. Customers are looking for suppliers capable of delivering consistent chemical composition, fine diameter tolerance, and smooth surface finish—all areas where DLX excels.

Our manufacturing process combines advanced vacuum melting with precision drawing and heat treatment, resulting in wire that delivers the best possible dimensional stability, even under demanding thermal cycles.

Element	Typical Content (%)	Function
Nickel (Ni)	36	Controls the thermal expansion coefficient
Iron (Fe)	Balance	Provides structure and strength
Carbon (C)	≤0.05	Improves hardness and processability
Manganese (Mn)	≤0.5	Enhances workability
Silicon (Si)	≤0.3	Improves oxidation resistance

DLX’s Invar 36 (4J36) wire stands out for its precision and reliability. We control every step of production—from raw material selection to final inspection—ensuring that each batch meets tight mechanical and thermal specifications.

Why DLX 4J36 Wire Performs Better:

• Advanced melting and refining: We use vacuum induction melting and refining to ensure purity and stability.

• Consistent expansion control: Our alloy maintains uniform thermal expansion rates across different batches.

• High precision drawing: Produces wires with tight diameter tolerances and smooth surfaces for superior electrical and mechanical performance.

• Custom finishing: Options include bright annealed, oxide-free, or polished surfaces for specific engineering needs.

• Reliable technical support: Our metallurgical team provides expert consultation for your design and processing requirements.

• Global reach: DLX ensures stable supply, fast delivery, and responsive customer service for both small and bulk orders.

Comparative Data Table

Invar 36 offers the lowest thermal expansion among these alloys, making it the preferred choice for applications requiring the highest level of precision and dimensional consistency.

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 makes Invar 36 (4J36) special?
It’s a nickel-iron alloy engineered to have an extremely low coefficient of thermal expansion, maintaining precise dimensions across wide temperature changes.

2. What industries commonly use Invar 36 wire?
It’s widely used in aerospace, optical devices, precision instruments, and cryogenic systems that require dimensional accuracy.

3. How is DLX’s Invar 36 wire different from standard grades?
DLX maintains tighter control over composition, surface finish, and mechanical performance through advanced melting and precision drawing processes.

4. Can Invar 36 wire be welded or soldered?
Yes. It can be welded using TIG, MIG, or resistance welding under protective atmospheres to prevent oxidation.

5. What is the operating temperature range of Invar 36?
It performs best between −250°C and +300°C, maintaining minimal thermal expansion across this range.

6. Is Invar 36 magnetic?
It is weakly magnetic at room temperature and gradually loses magnetism as temperature increases.

7. Can DLX supply custom wire sizes and finishes?
Absolutely. We can provide custom diameters, coil forms, and surface finishes based on your technical specifications.

8. What quality standards does DLX Invar 36 wire meet?
DLX 4J36 wire conforms to GB/T 14986, ASTM F1684, and other relevant international standards for controlled expansion alloys.

Market Outlook

The global demand for Invar 36 is expanding rapidly as industries pursue higher accuracy and miniaturization. From aerospace navigation to high-end optical calibration, precision alloys like Invar 36 are essential for the next generation of scientific and industrial technologies.

DLX is actively developing next-level manufacturing solutions to enhance purity, surface smoothness, and formability of Invar wire. Our ongoing investment in research and testing ensures that our customers receive not just reliable materials—but performance that exceeds expectations in every critical environment.