Alloy 27，Glass sealing 27 Alloy Tube，

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Alloy 27 (Glass Sealing 27 Alloy Wire) - Introduction with Composition, Properties, Applications and Product Forms

Alloy 27, commercially known as Glass Sealing 27 Alloy, is a specialized iron-nickel alloy renowned for its precise coefficient of thermal expansion (CTE) that matches various glass types, making it indispensable for glass-to-metal sealing applications. This high-performance alloy combines excellent glass sealing compatibility with good mechanical strength, corrosion resistance, and superior formability, and 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. Glass Sealing 27 Alloy Wire, in particular, is valued for its precision, flexibility, and consistent thermal expansion properties, making it ideal for intricate glass-sealed components in electronics, telecommunications, and lighting industries. Below is a detailed overview of its chemical composition, key properties, practical applications, and available product forms.

Chemical Composition

The precisely engineered chemical composition of Alloy 27 (Glass Sealing 27 Alloy) is the foundation of its exceptional glass sealing compatibility and mechanical performance. The typical composition (by weight) is as follows:

Iron (Fe): 71-73% (primary matrix element, providing structural strength and stability)

Nickel (Ni): 26-28% (critical for achieving a controlled coefficient of thermal expansion that matches glass, enabling strong glass-to-metal bonds)

Carbon (C): ≤ 0.03% (strictly controlled to avoid carbide formation, which could disrupt thermal expansion uniformity)

Manganese (Mn): ≤ 0.5% (assists in deoxidation during manufacturing and improves weldability without altering CTE)

Silicon (Si): ≤ 0.2% (minimized to prevent the formation of brittle silicides, preserving ductility and sealing integrity)

Sulfur (S): ≤ 0.01% (kept at very low levels to ensure good ductility and prevent hot shortness during fabrication)

Phosphorus (P): ≤ 0.02% (controlled to maintain thermal expansion stability and avoid embrittlement)

Other trace elements: ≤ 0.3% total (including chromium and copper, all minimized to preserve the alloy’s precise CTE)

This carefully balanced composition synergistically delivers the alloy's signature glass sealing compatibility, good mechanical strength, and formability, making it suitable for precision glass-to-metal sealing applications.

Key Properties

Alloy 27 (Glass Sealing 27 Alloy Wire) and its various forms exhibit a unique set of properties that make them indispensable in glass sealing and precision engineering applications:

Mechanical Properties (room temperature, annealed condition):

Tensile strength: 400-530 MPa (58,000-76,900 psi)

Yield strength (0.2% offset): 130-220 MPa (18,800-31,900 psi)

Elongation (in 50 mm): 30-45% (excellent ductility, enabling complex forming, bending, and drawing into wire and thin forms for intricate seals)

Hardness: 100-140 HB (Brinell hardness, indicating good machinability and workability)

Thermal Properties (critical for glass sealing):

Coefficient of thermal expansion (CTE): Closely matched to borosilicate and soda-lime glasses, with a CTE of 8.5-9.5 μm/(m·K) over the temperature range of 20°C to 300°C (68°F to 572°F), ensuring strong, stress-free glass-to-metal bonds

Curie temperature: 100-120°C (212-248°F), below which the alloy retains its magnetic properties (if required for specific applications)

Thermal conductivity: 16 W/(m·K) at 20°C (68°F), facilitating uniform heat distribution during sealing processes

Specific heat capacity: 450 J/(kg·K) at 20°C (68°F)

Corrosion Resistance:

General corrosion resistance: Good resistance to atmospheric corrosion, freshwater, and mild industrial environments, ensuring long-term seal integrity

Chemical resistance: Resistant to dilute acids, alkaline solutions, and organic chemicals; suitable for sealed environments with minimal exposure to strong oxidizers

Wet corrosion: Resistant to oils, solvents, and mild detergents, ensuring durability in electronic and lighting components

Oxidation resistance: Moderate resistance to oxidation in air up to 300°C (572°F), forming a thin oxide layer that does not interfere with glass bonding

Physical Properties:

Density: 7.9 g/cm³ (0.285 lb/in³)

Melting point: 1450-1490°C (2642-2714°F)

Modulus of elasticity: 140 GPa (20,300 ksi) at room temperature

Electrical resistivity: 0.45-0.55 μΩ·m at 20°C (68°F)

Product Forms

Alloy 27 (Glass Sealing 27 Alloy) is manufactured in a diverse range of forms to accommodate specialized glass sealing and precision engineering processes across electronics, telecommunications, and lighting sectors:

Bar: Available as Round bar (diameters from 6 mm to 200 mm) and Flat bar (thickness 5 mm to 100 mm, width 15 mm to 500 mm), ideal for machining into glass-sealed connectors, sensor housings, and precision hardware.

Ribbon: Thin, flat strips (thickness 0.05 mm to 1 mm, width 5 mm to 100 mm) used in flat glass seals, electrical feedthroughs, and bimetallic components requiring glass bonding.

Wire: Glass Sealing 27 Alloy Wire (diameters 0.05 mm to 8 mm) offers excellent flexibility and precise CTE, making it suitable for lead wires in vacuum tubes, fiber optic connectors, and miniature glass-sealed sensors.

Rods: Solid cylindrical rods (diameters 3 mm to 50 mm) suitable for structural supports in glass-sealed assemblies, electrical terminals, and lighting components.

Tube and Pipe: Seamless options (outer diameter 5 mm to 150 mm, wall thickness 0.5 mm to 8 mm) for glass-sealed fluid transport systems, vacuum feedthroughs, and protective enclosures.

Foil: Ultra-thin sheets (thickness 0.005 mm to 0.1 mm) used in lightweight glass-sealed electrical contacts, microelectronic packages, and thin-film seals.

Plate and Sheet: Flat forms (plate: thickness 4 mm to 80 mm; sheet: 0.2 mm to 4 mm) for fabricating glass-sealed panels, optical windows, and electronic enclosures.

Strip: Narrow, flat strips (thickness 0.05 mm to 2 mm, width 10 mm to 200 mm) for precision manufacturing in glass-sealed relays, switches, and sensor leads.

Forging Stock: Billets and ingots for hot forging into complex shapes such as glass-sealed aerospace connectors, industrial valve components, and high-pressure seals.

Applications

The exceptional glass sealing properties of Alloy 27 (Glass Sealing 27 Alloy Wire) across its various forms make it a critical material in industries requiring reliable glass-to-metal bonds and precision engineering:

Electronics and Telecommunications:

Vacuum tubes and electron devices: Wire and rod leads sealed into glass envelopes, ensuring vacuum integrity and electrical conductivity.

Fiber optic connectors: Components (from bar and wire) for glass-sealed fiber optic cables, maintaining signal integrity and environmental protection.

Sensor packages: Glass-sealed housings (from plate and sheet) for pressure, temperature, and humidity sensors, protecting sensitive electronics from external environments.

Lighting and Optics:

Light bulbs and discharge lamps: Wire leads and mounts (from wire and ribbon) sealed into glass bulbs, ensuring electrical connection and hermetic sealing.

Optical instruments: Glass-sealed windows and prisms (from plate and foil) in spectrometers and lasers, providing clear optical paths with environmental protection.

LED packaging: Sealed components (from strip and foil) for high-power LEDs, ensuring thermal management and moisture resistance.

Aerospace and Industrial:

Aerospace connectors: Glass-sealed electrical feedthroughs (from bar and tube) in aircraft and satellite systems, withstanding extreme temperature and pressure changes.

Industrial sensors: Glass-sealed pressure and level sensors (from rod and sheet) for harsh industrial environments, ensuring accurate readings and durability.

Nuclear instrumentation: Hermetically sealed components (from forging stock and pipe) for radiation detectors, protecting sensitive materials from contamination.

Specialized Applications by Form:

Wire: Lead wires in glass-sealed electronic components, fiber optic cable cores, and miniature sensor leads.

Ribbon and Strip: Flat seals in electrical feedthroughs, bimetallic glass-sealed switches, and precision connectors.

Plate and Sheet: Glass-sealed panels in optical instruments, sensor housings, and industrial enclosures.

Bar and Rod: Machined glass-sealed connectors, valve stems, and structural components in aerospace and industrial systems.

In summary, Alloy 27 (Glass Sealing 27 Alloy Wire) — available in forms from Bar and Wire to Plate and Forging Stock — delivers exceptional glass-to-metal sealing compatibility, good mechanical strength, and formability. Its diverse product forms enable tailored solutions across electronics, lighting, aerospace, and industrial sectors, establishing it as a critical material in applications demanding reliable glass-sealed components.

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 2746 gallon liquid totes Special package is available on request.