4J29 Strips: Precision Expansion Control and Vacuum-Seal Performance
Product Overview
Expansion Alloy 4J29 Strips (UNS K94610) are wrought iron-nickel-cobalt alloys designed for high-integrity glass-to-metal sealing applications. Their precise 29 % Ni and 17 % Co matrix balances thermal expansion to match hard glass and ceramic (5.0 × 10⁻⁶/°C at 20–300 °C; 5.2 × 10⁻⁶/°C at 20–450 °C), minimizing thermal stress during cycling. Trace controls of carbon, phosphorus, and sulfur (each ≤ 0.02 %) eliminate brittleness and ensure a dense oxide film for excellent glass wetting and corrosion resistance in mild atmospheres. In the annealed state, strips exhibit a yield strength of 340 MPa, tensile strength of 520 MPa, and elongation of 42 %, enabling deep drawing, stamping, and fine blanking without cracking. A Curie point at 430 °C ensures magnetic stability, while a density of 8.17 g/cm³ and thermal conductivity of 20.3 W/m·°C support reliable thermal management. Available in cold-rolled gauges (0.1–5 mm thick, up to 300 mm wide) with 2B/2E finishes, 4J29 Strips meet stringent ASTM F15 and UNS K94610 specifications, fulfilling the exacting demands of vacuum tubes, microelectronics lead frames, flash bulb bases, hermetic connectors, and other critical components across global industries.
Chemical Composition
Mechanical Properties
Physical Properties
Conformance Standards
Applications
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Vacuum & Electronic Sealing: Hermetic feedthroughs, vacuum tube envelopes, transistor headers
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Integrated Circuits: Lead frames and flat-pack packages requiring matched CTE
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Photography & Lighting: Flash bulb bases and lamp caps for reliable glass sealing
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Sensor & Medical Devices: Glass-sealed pressure sensors and implantable electronics
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Aerospace & Defense: High-power transmitting valves and ceramic-metal interfaces
Frequently Asked Questions
Q1: How closely does 4J29 match glass expansion?
A1: 4J29 Strips exhibit a mean linear CTE of 5.0 × 10⁻⁶/°C (20–300 °C) and 5.2 × 10⁻⁶/°C (20–450 °C), matching borosilicate glass to within ± 0.2 × 10⁻⁶/°C.
Q2: Can 4J29 Strips be welded to Kovar or stainless?
A2: Yes—TIG/GTAW and electron-beam welding join 4J29 to similar alloys without altering thermal expansion, preserving hermeticity.
Q3: What tolerances are available?
A3: Supplied in 0.1–5 mm thicknesses with width tolerances ± 0.1 mm and coil lengths to customer spec; exact tolerances per ASTM F15.
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