Alloy 42,Nilo 42 Rod,UNS K94100

Alloy 42,Low expansion 42 Alloy Wire,UNS K94100

Alloy 42 (Low Expansion 42 Alloy Wire, UNS K94100) - Introduction with Composition, Properties, Applications and Product Forms

Alloy 42, commercially known as Low Expansion 42 Alloy and designated by UNS K94100, is a nickel-iron alloy celebrated for its extremely low and tightly controlled coefficient of thermal expansion (CTE), making it a cornerstone material in applications where dimensional stability across wide temperature ranges is non-negotiable. This alloy is specifically engineered to minimize thermal expansion and contraction, ensuring reliability in high-precision assemblies that demand consistent performance under varying thermal conditions. 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. Low Expansion 42 Alloy Wire, in particular, is valued for its uniform thermal properties, flexibility, and precision, making it ideal for intricate components 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 Alloy 42 (Low Expansion 42 Alloy, UNS K94100) is the foundation of its exceptional low thermal expansion and mechanical stability. The typical composition (by weight) is as follows:

Nickel (Ni): 41-43% (the primary element responsible for the alloy’s ultra-low CTE, enabling precise thermal control)

Iron (Fe): 57-59% (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)

This carefully engineered nickel-iron blend delivers the alloy's signature low thermal expansion, ensuring compatibility with materials like alumina ceramics, certain glasses, and high-strength steels in applications where temperature variations are common.

Key Properties

Alloy 42 (Low Expansion 42 Alloy Wire, UNS K94100) and its various forms exhibit a unique set of properties that make them indispensable in applications requiring precise thermal expansion control:

Thermal Expansion Properties:

Coefficient of thermal expansion (CTE):

20-300°C: 4.0-5.0 × 10⁻⁶ /°C (among the lowest for structural alloys, minimizing dimensional changes under thermal stress)

20-400°C: 4.5-5.5 × 10⁻⁶ /°C (maintains ultra-low expansion at moderately elevated temperatures)

Thermal conductivity: 16-18 W/(m·K) at 20°C (68°F)

Melting point: 1430-1470°C (2594-2678°F)

Curie temperature: 380-400°C (the temperature above which ferromagnetic properties diminish)

Mechanical Properties (annealed condition):

Tensile strength: 380-480 MPa (55,100-69,600 psi)

Yield strength (0.2% offset): 120-190 MPa (17,400-27,600 psi)

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

Hardness: 105-145 HB (Brinell hardness, reflecting good machinability and workability)

Physical and Magnetic Properties:

Density: 7.8-8.0 g/cm³ (0.282-0.289 lb/in³)

Modulus of elasticity: 165-175 GPa (23,900-25,400 ksi) at room temperature

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

Product Forms

Alloy 42 (Low Expansion 42 Alloy, UNS K94100) is manufactured in a diverse range of forms to accommodate specialized applications requiring ultra-low thermal expansion:

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 precision hardware, structural components, and thermal management parts.

Ribbon: Thin, flat strips (thickness 0.01 mm to 0.5 mm, width 1 mm to 100 mm) used in electronic packaging, thermostats, and precision seals requiring tight thermal expansion control.

Wire: Low Expansion 42 Alloy Wire (diameters 0.02 mm to 5 mm) offers consistent thermal properties and flexibility, suitable for thermocouple leads, precision coils, and wire bonds in electronics.

Rods: Solid cylindrical rods (diameters 2 mm to 30 mm) used in ceramic-to-metal seals, sensor supports, and calibration tools.

Tube and Pipe: Hollow forms (outer diameter 3 mm to 100 mm, wall thickness 0.1 mm to 5 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 20 mm; sheet: 0.05 mm to 1 mm) for fabricating flanges, heat sinks, and structural parts in optical and electronic equipment.

Strip: Narrow, flat strips (thickness 0.05 mm to 1 mm, width 2 mm to 100 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 thermal systems.

Applications

The ultra-low thermal expansion and mechanical stability of Alloy 42 (Low Expansion 42 Alloy Wire, UNS K94100) across its various forms make it a critical material in industries requiring precision thermal management and dimensional stability:

Electronics and Telecommunications:

Ceramic-to-metal seals: Components (from bar, rod, and wire) for vacuum tubes, connectors, and feedthroughs, where the alloy’s ultra-low CTE matches alumina ceramics to prevent seal failure.

Electronic packaging: Leadframes, headers, and heat sinks (from sheet, strip, and plate) for semiconductors, ensuring dimensional stability during soldering and operation.

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

Aerospace and Aviation:

Optical systems: Structural components for telescopes, laser systems, and avionics displays (from plate, sheet, and bar) where minimal thermal expansion is critical to maintaining optical alignment.

Thermal management: Heat shields, thermal sleeves, and ducting (from tube, sheet, and strip) for aircraft engines and avionics, ensuring compatibility with adjacent materials.

Instrumentation: Precision coils, connectors, and wiring (from wire and ribbon) for aerospace sensors and navigation systems, resisting thermal stress.

Optical and Medical Devices:

Optical assemblies: Mounts, brackets, and seals (from bar, plate, and strip) for lenses, mirrors, and fiber optic systems, maintaining alignment across temperature ranges.

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

Laboratory instruments: Seals, valves, and structural parts (from forging stock, bar, and tube) for spectrometers and analytical devices, ensuring measurement accuracy.

Automotive and Industrial:

Automotive electronics: Sensors, connectors, and thermal management components (from strip, wire, and sheet) for engine control units and advanced driver-assistance systems (ADAS).

Thermostats and bimetals: Ribbon and strip forms used in temperature-regulating devices, leveraging ultra-low expansion to actuate switches.

Vacuum systems: Seals, flanges, and tubing (from tube, bar, and plate) for industrial vacuum chambers, preventing leaks due to thermal cycling.

Specialized Applications by Form:

Wire: Thermocouple leads, precision coils, and wire bonds in electronics and sensors.

Ribbon/Strip: Bimetallic elements, seals, and leadframes for electronic packaging.

Tube/Pipe: Protective tubing for sensors, thermal sleeves, and vacuum system components.

Plate/Sheet: Structural parts for optical systems, heat sinks, and aerospace instrumentation.

In summary, Alloy 42 (Low Expansion 42 Alloy Wire, UNS K94100) — available in forms from Bar and Wire to Plate and Forging Stock — delivers exceptional ultra-low thermal expansion, mechanical stability, and material compatibility. Its diverse product forms enable tailored solutions across electronics, aerospace, optical, and medical sectors, establishing it as a critical material in applications requiring precision thermal management and dimensional stability.

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 1499 gallon liquid totes Special package is available on request.