4J50 Expansion Alloys 590–700 MPa Tensile Excellent Formability Thermal Stability

4J50 Strips: 590–700 MPa Tensile and Excellent Formability and Thermal Stability

Product Overview

Expansion Alloy 4J50 Strips (UNS K94610) are wrought Fe–Ni–Co alloys formulated to match the CTE of soft sealing glasses and ceramics. Their optimized chemistry—Ni 50.5 %, Mn 0.60 %, Si 0.30 %, C 0.05 %, Cr 0.25 %, P 0.025 %, S 0.025 %, Al 0.10 %, Co 1.0 %, balance Fe—yields a stable CTE of 9.8 × 10⁻⁶ /°C from 20 → 100 °C rising gently to 10.6 × 10⁻⁶ /°C at 600 °C, ensuring virtually zero thermal stress in glass-to-metal seals. These strips maintain hermeticity and corrosion resistance in vacuum and mild-atmosphere environments, with a Curie point exceeding 400 °C for magnetic stability. Available in cold-rolled thicknesses from 0.2 mm to 3.5 mm and widths to 300 mm, 4J50 Strips form readily via stamping, slitting, and fine-blanking, producing diaphragms, bellows, feedthroughs, and sensor housings with tight tolerances. Heat-treat per YB/T 5235-2005 (900 °C × 1 h in H₂, controlled cool) to achieve “soft” or “hard” tempers, tailoring tensile strength (< 590 MPa soft; > 700 MPa hard) to application needs.

Chemical Composition

Mechanical Properties

Physical Properties

Conformance Standards

• YB/T 5235-2005 – Chinese standard for constant-expansion alloys

• ASTM F15 – Controlled-expansion alloys for seals

• UNS K94610 / W.No. 1.3981 – Material designation for 4J50

Applications

• Electric Vacuum Industry: Vacuum tube seals, cathode‐ray feedthroughs

• Hermetic Electronic Packages: Power semiconductor housings, sensor feedthroughs

• Precision Instrumentation: Bellows, diaphragms, micro-valve components

• Aerospace & Defense: High-power RF windows, avionics glass seals

• Optoelectronics: LED and laser diode hermetic enclosures

Frequently Asked Questions

Q1: What temperature range is 4J50 effective for?
A1: Continuous service from –60 °C to 400 °C with a stable CTE; intermittent exposures up to 600 °C maintain hermeticity.

Q2: How is “soft” vs. “hard” temper achieved?
A2: Anneal at 900 °C for 1 h in H₂, then cool ≤ 5 °C/min to 200 °C for “soft”; age or cold-work plus re-anneal yields “hard” (> 700 MPa tensile).

Q3: Can 4J50 Strips be welded to Kovar or stainless?
A3: Yes—TIG/GTAW and electron-beam methods join 4J50 to similar alloys and stainless steels without altering CTE or hermetic seal performance.

0.6mm Expansion Alloys

0.8mm Expansion Alloys

0.9mm invar steel

4J50 Expansion Alloys 590–700 MPa Tensile Excellent Formability Thermal Stability Images