Kovar,Alloy K Bar(Round bar, Flat bar),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)

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 1402 gallon liquid totes Special package is available on request.