High Precision 4J33 Sealing Wire Controlled Expansion Alloy For Hermetic Packaging

Product Overview

4J33 alloy wire is a precision low-expansion Fe-Ni-Co alloy material specifically designed for hermetic glass-to-metal sealing applications. With approximately 33% nickel and a small amount of cobalt, this alloy offers a thermal expansion coefficient closely matched to hard glass and ceramics. It is widely used in the manufacture of vacuum tubes, infrared sensors, electronic relays, and other high-reliability devices.

Material Composition

• Nickel (Ni): ~33%

• Cobalt (Co): ~3–5%

• Iron (Fe): Balance

• Others: Mn, Si, C (trace amounts)

Thermal Expansion (30–300°C): ~5.3 × 10⁻⁶ /°C
Density: ~8.2 g/cm³
Electrical Resistivity: ~0.48 μΩ·m
Tensile Strength: ≥ 450 MPa
Magnetic Properties: Soft magnetic, good permeability and stability

Available Specifications

• Diameter: 0.02 mm to 3.0 mm

• Surface: Bright, oxide-free

• Delivery form: Coils, spools, or cut length

• Condition: Annealed or cold-drawn

• Custom sizes and packaging available

Key Features

• Excellent match with hard glass for vacuum-tight sealing

• Stable thermal expansion for precision components

• Good corrosion resistance and weldability

• Clean surface finish, vacuum-compatible

• Reliable performance in aerospace and electronic applications

Typical Applications

• Glass-to-metal hermetic seals

• Vacuum tubes and infrared sensors

• Relay housings and electronic packaging

• Optical device enclosures

• Aerospace-grade connectors and leads

Packaging & Shipping

• Standard plastic spool, vacuum-sealed or custom packaging

• Delivery via air, sea, or express

• Lead time: 7–15 working days depending on order size