Kovar,Rodar Wire,UNS K94610

Kovar,Rodar Wire,UNS K94610

Kovar, Rodar Wire, UNS K94610 - Introduction with Composition, Properties, Applications and Product Forms

Kovar, commercially known as Rodar Wire and designated by UNS K94610, is a nickel-iron-cobalt alloy celebrated for its exceptional thermal expansion matching with hard glass, making it a critical material in high-integrity glass-to-metal sealing applications. This alloy is specifically engineered to exhibit a coefficient of thermal expansion (CTE) that closely aligns with borosilicate glass (such as Pyrex), ensuring the formation of durable, hermetic seals even under extreme temperature fluctuations. It is available in a comprehensive range of forms to meet diverse industrial needs, including Bar (Round bar, Flat bar), Ribbon, Wire, Rods, Tube, Pipe, Foil, Plate, Sheet, Strip, and Forging Stock. Rodar Wire, in particular, is valued for its uniform thermal properties, flexibility, and precision, making it ideal for intricate seals, fine wire components, and precision assemblies in electronics, aerospace, and optical industries. Below is a detailed overview of its chemical composition, key properties, practical applications, and available product forms.

Chemical Composition

The precisely balanced chemical composition of Kovar (Rodar Wire, UNS K94610) is the foundation of its exceptional glass-matching thermal expansion and mechanical reliability. The typical composition 

(by weight) is as follows:

Nickel (Ni): 28-30% (a key element contributing to controlled thermal expansion and corrosion resistance)

Iron (Fe): 53-55% (balances the alloy, providing structural strength and supporting thermal stability)

Cobalt (Co): 16-18% (critical for fine-tuning the CTE to match hard glass, enhancing seal integrity)

Carbon (C): ≤ 0.03% (kept extremely low to avoid carbide formation, which can disrupt thermal uniformity)

Manganese (Mn): ≤ 0.5% (aids in deoxidation during manufacturing, improving ductility and reducing inclusions)

Silicon (Si): ≤ 0.3% (controlled to prevent oxide formation that could compromise glass-to-metal bonding)

Sulfur (S): ≤ 0.01% (strictly limited to ensure good ductility and prevent embrittlement, critical for forming)

Phosphorus (P): ≤ 0.02% (kept low to preserve corrosion resistance and avoid grain boundary weakness)

This carefully engineered nickel-iron-cobalt blend delivers the alloy's signature thermal expansion characteristics, ensuring a near-perfect match with borosilicate glass—key to creating hermetic seals that withstand thermal cycling without cracking.

Key Properties

Kovar (Rodar Wire, UNS K94610) and its various forms exhibit a unique set of properties that make them indispensable in glass-to-metal sealing and precision thermal applications:

Thermal Expansion Properties:

Coefficient of thermal expansion (CTE):

20-300°C: 5.0-6.0 × 10⁻⁶ /°C (precisely tuned to match borosilicate glass, minimizing stress in seals during temperature changes)

20-400°C: 5.5-6.5 × 10⁻⁶ /°C (maintains compatibility with glass at moderately elevated temperatures)

Thermal conductivity: 17-19 W/(m·K) at 20°C (68°F)

Melting point: 1420-1460°C (2588-2660°F)

Curie temperature: 450-470°C (the temperature above which ferromagnetic properties diminish)

Mechanical Properties (annealed condition):

Tensile strength: 440-540 MPa (63,800-78,300 psi)

Yield strength (0.2% offset): 170-240 MPa (24,700-34,800 psi)

Elongation (in 50 mm): 25-35% (excellent ductility, enabling forming into fine wires, thin ribbons, and complex seal geometries)

Hardness: 120-160 HB (Brinell hardness, reflecting good machinability and workability for precision components)

Physical and Magnetic Properties:

Density: 8.3-8.5 g/cm³ (0.299-0.307 lb/in³)

Modulus of elasticity: 170-180 GPa (24,600-26,100 ksi) at room temperature

Magnetic permeability: Ferromagnetic at room temperature, with high permeability (useful in magnetic sealing applications)

Corrosion resistance: Good resistance to atmospheric corrosion, moisture, and mild chemicals, ensuring long-term seal integrity; limited resistance to strong acids and alkalis.

Sealing Compatibility:

Glass types: Optimally matched to borosilicate glass (e.g., Pyrex), with good compatibility with other hard glasses, forming hermetic seals with minimal stress

Seal strength: Maintains bond integrity through thermal cycling (-55°C to 300°C), vibration, and pressure changes, critical for vacuum and pressurized systems

Product Forms

Kovar (Rodar Wire, UNS K94610) is manufactured in a diverse range of forms to accommodate specialized glass-sealing and precision thermal applications:

Bar: Available as Round bar (diameters from 5 mm to 100 mm) and Flat bar (thickness 3 mm to 50 mm, width 10 mm to 200 mm), ideal for machining into seal headers, flanges, and structural components for glass-to-metal assemblies.

Ribbon: Thin, flat strips (thickness 0.01 mm to 0.5 mm, width 1 mm to 100 mm) used in flat seals, electronic packaging, and miniature glass-to-metal connections requiring uniform contact.

Wire: Rodar Wire (diameters 0.02 mm to 5 mm) offers exceptional uniformity and flexibility, suitable for fine wire seals, thermocouple leads, and wire bonds in vacuum tubes and sensors.

Rods: Solid cylindrical rods (diameters 2 mm to 30 mm) used in pin seals, feedthroughs, and precision glass-mounting components.

Tube and Pipe: Hollow forms (outer diameter 3 mm to 100 mm, wall thickness 0.1 mm to 5 mm) for glass-encased tubing, protective sleeves, and vacuum feedthroughs.

Foil: Ultra-thin sheets (thickness 0.001 mm to 0.1 mm) used in flexible seals, thin-film electronics, and lightweight glass-to-metal laminates.

Plate and Sheet: Flat forms (plate: thickness 1 mm to 20 mm; sheet: 0.05 mm to 1 mm) for fabricating large seals, optical instrument housings, and display panels with glass integration.

Strip: Narrow, flat strips (thickness 0.05 mm to 1 mm, width 2 mm to 100 mm) for precision components such as relay seals, lamp bases, and sensor connectors.

Forging Stock: Billets and ingots for hot forging into custom shapes, such as large flanges and complex seal structures for industrial glass systems.

Applications

The exceptional glass-matching properties and reliability of Kovar (Rodar Wire, UNS K94610) across its various forms make it a critical material in industries requiring hermetic glass-to-metal seals:

Electronics and Telecommunications:

Vacuum tubes and electron devices: Seal pins, headers, and feedthroughs (from wire, rod, and bar) for vacuum tubes, klystrons, and magnetrons, ensuring airtight operation.

Sensor packaging: Hermetic seals for pressure sensors, temperature sensors, and MEMS devices (from ribbon, wire, and sheet), protecting sensitive electronics from moisture and contaminants.

Connectors and feedthroughs: Glass-sealed electrical connectors (from bar, tube, and strip) for aerospace, marine, and industrial equipment, preventing signal degradation.

Optical and Photonics:

Optical fibers: Glass-to-metal seals for fiber optic connectors and feedthroughs (from tube, wire, and ribbon), maintaining light transmission integrity in harsh environments.

Laser systems: Seals and structural components (from plate, bar, and forging stock) for laser diodes and optical amplifiers, ensuring alignment stability.

Display technology: Seals for high-temperature displays and optical windows (from sheet, foil, and strip), integrating glass and metal components without thermal stress.

Aerospace and Defense:

Avionics: Hermetic seals for radar components, navigation systems, and communication devices (from plate, bar, and tube) operating in extreme environments.

Missile and spacecraft systems: Pressure-tight seals for guidance systems, thermal sensors, and fuel monitoring equipment (from forging stock, rod, and wire).

Military communication: Glass-sealed connectors and feedthroughs (from strip, bar, and tube) for secure radio systems and underwater communication devices.

Medical and Industrial:

Medical devices: Hermetic seals for pacemakers, implantable sensors, and diagnostic equipment (from wire, ribbon, and tube), ensuring biocompatibility and long-term reliability.

Industrial vacuum systems: Seals for vacuum chambers, plasma processing equipment, and semiconductor manufacturing tools (from plate, tube, and bar).

Energy systems: Glass-to-metal seals for batteries, fuel cells, and solar panel components (from sheet, strip, and wire), withstanding thermal cycling and chemical exposure.

Specialized Applications by Form:

Wire: Fine pin seals in microelectronics, thermocouple leads in glass-encased sensors, and wire bonds in vacuum devices.

Ribbon/Strip: Flat seals in batteries, lamp bases, and relay contacts requiring uniform glass contact.

Tube/Pipe: Vacuum feedthroughs, protective sleeves for optical fibers, and gas-tight tubing in analytical instruments.

Plate/Sheet: Large glass-sealed panels for display systems, optical instrument housings, and industrial furnace windows.

In summary, Kovar (Rodar Wire, UNS K94610) — available in forms from Bar and Wire to Plate and Forging Stock — delivers exceptional glass-matching thermal expansion, hermetic sealing capability, and mechanical reliability. Its diverse product forms enable tailored solutions across electronics, optics, aerospace, and medical sectors, establishing it as a critical material in applications requiring durable glass-to-metal integration.

Packing of Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 1440 gallon liquid totes Special package is available on request.