Low Expansion Ceramic Seal Expansion Alloys 4J33 Strips 500-1000 MPa

4J33 Strips: Low-Expansion Ceramic Seal and Excellent Formability

Product Overview

Expansion Alloy 4J33 Strips (UNS K94610) are wrought iron-nickel-cobalt alloys tailor-made for glass-to-metal and ceramic-to-metal sealing. Their precise chemistry—32.1–33.6 % Ni and 14.0–15.2 % Co, with C, P, S ≤ 0.05 %—creates a CTE of 6.3 × 10⁻⁶ /°C (20–400 °C) to 8.5 × 10⁻⁶ /°C (20–600 °C), closely matching 95 % Al₂O₃ ceramics and minimizing thermal mismatch stresses. In the annealed “soft” delivery condition, 4J33 Strips achieve tensile strengths < 570 MPa and yield strengths commensurate with high-integrity seals; a “hard” temper raises tensile strength > 700 MPa for demanding structural applications. Exceptional elongation (up to 42 %) and hardness (~ 78 HB) enable fine blanking, deep drawing, and stamping of diaphragms, bellows, and precision feedthrough parts. Physical stability is assured by a melting range near 1450 °C, density of 8.27 g/cm³, thermal conductivity of 17.6 W/m·°C, and resistivity of 0.46 µΩ·m. Supplied in cold-rolled gauges (0.1–3.5 mm thick, widths up to 300 mm), these strips meet ASTM F15 (controlled-expansion alloys) and UNS K94610 specifications, serving global markets from vacuum-tube manufacturing to implantable medical devices.

Chemical Composition

Mechanical Properties

Physical Properties

Conformance Standards

• ASTM F15 – Controlled-expansion alloy strip

• UNS K94610 / W. Nr. 1.3981 – Alloy designation

• YB/T 5231-2005 – Chinese sealing alloy standard

• DIN EN 601 – Ceramic-sealed alloy specifications

Applications

• Vacuum & Electronic Packaging – Hermetic feedthroughs, vacuum tube envelopes

• Aerospace Instruments – Engine sensor seals, satellite components

• Medical Devices – Implantable sensor housings, surgical instrument seals

• Industrial Sensors – High-precision pressure and temperature transducers

• Lighting & Photonics – Flash-lamp and photomultiplier tube bases

Frequently Asked Questions

Q1: How closely does 4J33 match ceramic CTE?
A1: 4J33 Strips exhibit a mean linear CTE of 6.3 × 10⁻⁶/°C (20–400 °C) to 8.5 × 10⁻⁶/°C (20–600 °C), matching 95 % Al₂O₃ within ± 0.2 × 10⁻⁶/°C.

Q2: Can 4J33 be welded or brazed?
A2: Yes—TIG, electron-beam welding, and active brazing alloys achieve hermetic bonds to Kovar, Invar, and stainless substrates without altering expansion properties.

Q3: What form factors are available?
A3: Cold-rolled strip in 0.1–3.5 mm thickness and up to 300 mm width; custom gauge, width, and finish per ASTM F15 and YB/T 5231 standards.

Low Expansion Alloys

4J33 Expansion Alloys

1000 MPa invar 36

Low Expansion Ceramic Seal Expansion Alloys 4J33 Strips 500-1000 MPa Images