Invar 36,Super Invar 32-5 Wire,UNS K93050

Invar 36,Super Invar 32-5 Wire,UNS K93050

Invar 36, Super Invar 32-5 Wire, UNS K93050 - Introduction with Composition, Properties, Applications and Product Forms

Invar 36, along with its high-performance variant Super Invar 32-5, designated by UNS K93050, is a family of nickel-iron alloys renowned for their near-zero coefficient of thermal expansion (CTE) at room temperature and below. This exceptional characteristic makes them indispensable in applications where dimensional stability across extreme temperature fluctuations is critical. Invar 36 is widely recognized for its low expansion properties, while Super Invar 32-5 offers even tighter control over thermal expansion, making it ideal for ultra-precision applications. Both alloys are 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. Super Invar 32-5 Wire, in particular, is valued for its uniform thermal properties, flexibility, and precision, making it ideal for intricate components in optics, aerospace, and electronics industries. Below is a detailed overview of their chemical composition, key properties, practical applications, and available product forms.

Chemical Composition

The precisely balanced chemical composition of Invar 36 and Super Invar 32-5 (UNS K93050) is the foundation of their exceptional low thermal expansion and mechanical stability. The typical composition 

(by weight) is as follows:

Invar 36:

Nickel (Ni): 35-37% (the primary element responsible for the alloy’s near-zero CTE, enabling exceptional thermal stability)

Iron (Fe): 63-65% (balances the alloy, providing structural strength and supporting thermal stability)

Carbon (C): ≤ 0.05% (kept 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 inclusions that could compromise thermal consistency)

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

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

Super Invar 32-5:

Nickel (Ni): 31-33% (optimized to achieve even lower thermal expansion than Invar 36)

Iron (Fe): 62-64%

Cobalt (Co): 4-6% (added to further reduce CTE and enhance thermal stability at low temperatures)

Carbon (C): ≤ 0.03%

Manganese (Mn): ≤ 0.3%

Silicon (Si): ≤ 0.2%

Sulfur (S): ≤ 0.01%

Phosphorus (P): ≤ 0.01%

These carefully engineered compositions deliver the alloys’ signature low thermal expansion, ensuring minimal dimensional changes across a wide temperature range and compatibility with materials like glass, ceramics, and certain metals in high-precision assemblies.

Key Properties

Invar 36, Super Invar 32-5 (including Super Invar 32-5 Wire, UNS K93050), and their various forms exhibit extraordinary properties that make them indispensable in applications requiring extreme thermal stability:

Thermal Expansion Properties:

Coefficient of thermal expansion (CTE):

Invar 36 (20-100°C): 0.5-1.5 × 10⁻⁶ /°C (near-zero, minimizing dimensional changes under thermal stress)

Super Invar 32-5 (20-100°C): 0.0-0.5 × 10⁻⁶ /°C (ultra-low, with virtually no expansion or contraction)

Invar 36 (20-300°C): 2.0-3.0 × 10⁻⁶ /°C (maintains low expansion at moderately elevated temperatures)

Super Invar 32-5 (20-300°C): 1.0-2.0 × 10⁻⁶ /°C (superior thermal stability at higher temperatures)

Thermal conductivity: 10-12 W/(m·K) at 20°C (68°F) for both alloys

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

Curie temperature: 230-250°C for Invar 36; 210-230°C for Super Invar 32-5 (the temperature above which ferromagnetic properties diminish)

Mechanical Properties (annealed condition):

Tensile strength:

Invar 36: 400-500 MPa (58,000-72,500 psi)

Super Invar 32-5: 420-520 MPa (60,900-75,400 psi)

Yield strength (0.2% offset):

Invar 36: 150-220 MPa (21,800-31,900 psi)

Super Invar 32-5: 160-230 MPa (23,200-33,400 psi)

Elongation (in 50 mm): 25-35% for both alloys (excellent ductility, enabling forming into wires, ribbons, and complex shapes)

Hardness:

Invar 36: 110-150 HB (Brinell hardness)

Super Invar 32-5: 120-160 HB (Brinell hardness) (both reflecting good machinability and workability)

Physical and Magnetic Properties:

Density:

Invar 36: 8.0-8.2 g/cm³ (0.289-0.296 lb/in³)

Super Invar 32-5: 8.1-8.3 g/cm³ (0.292-0.299 lb/in³)

Modulus of elasticity: 140-150 GPa (20,300-21,700 ksi) at room temperature for both alloys

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

Corrosion resistance: Good resistance to atmospheric corrosion and mild chemicals, ensuring durability in industrial environments; limited resistance to strong acids and alkalis.

Product Forms

Invar 36 and Super Invar 32-5 (UNS K93050) are manufactured in a diverse range of forms to accommodate specialized applications requiring extreme thermal stability:

Bar: Available as Round bar (diameters from 5 mm to 200 mm) and Flat bar (thickness 3 mm to 100 mm, width 10 mm to 500 mm), ideal for machining into precision hardware, structural components, and thermal management parts in optical and aerospace systems.

Ribbon: Thin, flat strips (thickness 0.01 mm to 0.5 mm, width 1 mm to 200 mm) used in electronic packaging, thermostats, and precision seals requiring near-zero expansion.

Wire: Super Invar 32-5 Wire (diameters 0.02 mm to 5 mm) offers exceptional uniformity and flexibility, suitable for fine coils, thermocouple leads, and wire bonds in ultra-precision instruments.

Rods: Solid cylindrical rods (diameters 2 mm to 50 mm) used in ceramic-to-metal seals, sensor supports, and calibration tools.

Tube and Pipe: Hollow forms (outer diameter 3 mm to 150 mm, wall thickness 0.1 mm to 10 mm) for thermal sleeves, protective tubing for sensors, and components in optical systems.

Foil: Ultra-thin sheets (thickness 0.001 mm to 0.1 mm) used in flexible thermal barriers, thin-film electronics, and precision gaskets.

Plate and Sheet: Flat forms (plate: thickness 1 mm to 50 mm; sheet: 0.05 mm to 1 mm) for fabricating optical mounts, laser components, and structural parts in aerospace instrumentation.

Strip: Narrow, flat strips (thickness 0.05 mm to 1 mm, width 2 mm to 200 mm) for precision components such as thermostat bimetals, relay contacts, and seal rings.

Forging Stock: Billets and ingots for hot forging into custom shapes, such as large flanges and structural components in aerospace and optical systems.

Applications

The near-zero thermal expansion and mechanical stability of Invar 36, Super Invar 32-5 (including Super Invar 32-5 Wire, UNS K93050) across their various forms make them critical materials in industries requiring extreme precision and thermal management:

Optical and Precision Instrumentation:

Optical systems: Mounts, brackets, and mirrors (from plate, bar, and sheet) for telescopes, microscopes, and laser systems, where minimal thermal expansion is critical to maintaining alignment.

Metrology equipment: Calibration standards, interferometer components, and precision scales (from bar, rod, and forging stock) requiring dimensional stability across temperature ranges.

Clock and watchmaking: Balance wheels, hairsprings, and precision gears (from wire, ribbon, and strip) ensuring accurate timekeeping regardless of temperature changes.

Aerospace and Aviation:

Aerospace structures: Components for satellite antennas, optical payloads, and navigation systems (from plate, bar, and forging stock) where thermal stability is critical in space and high-altitude environments.

Landing gear sensors: Thermal sleeves and protective tubing (from tube and wire) for sensors monitoring landing gear performance, resisting temperature fluctuations during flight.

Rocket and missile systems: Guidance system components and optical mounts (from plate, bar, and strip) maintaining precision during extreme thermal cycles.

Electronics and Telecommunications:

Semiconductor manufacturing: Precision tools and fixtures (from plate, bar, and rod) for wafer processing, ensuring dimensional stability during temperature-controlled processes.

Cryogenic equipment: Components for liquid nitrogen and helium systems (from tube, sheet, and wire) maintaining integrity at extremely low temperatures.

Thermal sensors: Thermocouple leads and sensor housings (from wire, ribbon, and tube) requiring accurate measurement without thermal expansion-induced errors.

Medical and Scientific Research:

Medical imaging: Components for MRI, CT scan, and laser-based medical devices (from sheet, tube, and wire) requiring dimensional stability in varying thermal environments.

Particle accelerators: Structural parts and vacuum seals (from plate, bar, and forging stock) maintaining precision in high-energy physics experiments.

Cryogenics research: Containers and tubing (from tube, sheet, and foil) for storing and transporting cryogenic fluids, resisting thermal contraction.

Specialized Applications by Form:

Wire: Fine coils in precision instruments, thermocouple leads in cryogenic sensors, and wire bonds in microelectronics.

Plate/Sheet: Optical mounts, laser components, and aerospace structural parts requiring extreme thermal stability.

Tube/Pipe: Cryogenic fluid transport, protective sleeves for optical fibers, and thermal management components.

Ribbon/Strip: Bimetallic elements in thermostats, precision seals in vacuum systems, and leadframes in high-stability electronics.

In summary, Invar 36 and Super Invar 32-5 (Super Invar 32-5 Wire, UNS K93050) — available in forms from Bar and Wire to Plate and Forging Stock — deliver exceptional near-zero thermal expansion, mechanical stability, and material compatibility. Their diverse product forms enable tailored solutions across optics, aerospace, electronics, and scientific sectors, establishing them as critical materials in applications requiring extreme precision and thermal management.

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 1496 gallon liquid totes Special package is available on request.