Introduction

4J36 Iron-Nickel Alloy (Invar 36) is a low expansion alloy with an ultra-low coefficient of thermal expansion. Controlling carbon and manganese is critical for its performance. Cold deformation can further reduce the expansion coefficient, while heat treatment within a specific range stabilizes it. The alloy resists corrosion in dry air at room temperature, but may rust in humid environments. Commonly used in LNG tanks, precision instruments, laser mounts, aerospace tooling, and bimetal strips. Available in sheet, plate, bar, wire, and forgings per GB/T or ASTM B753.

Chemical components(%)

Mechanical properties

Physical properties

4J36 Low Expansion Alloy Available Products and Standard

1. GB/T 15018 (Precision alloys – Low expansion alloys)

• Type: 

4J36 Iron-nickel Alloy Wire

4J36 Iron-nickel Alloy Strip

4J36 Iron-nickel Alloy Bar

4J36 Iron-nickel Alloy Sheet

• Size Range:

Wire: 0.1 – 15.0 mm dia

Strip: 0.05 – 5.0 mm thick × 5 – 500 mm wide

Bar: 8 – 355 mm dia

Sheet: 0.5 – 180 mm thick

• Surface: Annealed, Bright, Pickled, Ground

• Testing: Thermal expansion coefficient, chemical analysis, mechanical test, dimensional inspection, magnetic permeability (optional)

2. ASTM B753 (Standard Specification for Alloys with Controlled Expansion, Alloy 36 / Invar 36)

• Grade: Alloy 36 / 4J36 / FeNi36

• Type: Wire/Strip/Bar/Sheet

• Size Range:

Wire: 0.1 – 15.0 mm dia (coils or straight)

Strip: 0.05 – 5.0 mm thick × up to 500 mm wide (coils)

Bar: 8 – 355 mm dia (cold drawn or hot rolled)

Sheet: 0.5 – 180 mm thick (cold rolled or hot rolled)

• Surface: Annealed, Bright, Pickled, Polished

• Testing: Thermal expansion coefficient test (α value), chemical analysis, mechanical test, dimensional inspection, optional magnetic permeability

Advantages

(1) Ultra-low thermal expansion: 4J36 round bar and sheet maintain near‑constant dimensions from cryogenic temperatures up to 260°C, making them ideal for precision instruments and LNG storage.

(2) Excellent dimensional stability: This low‑expansion iron‑nickel alloy (Invar 36) minimizes thermal growth in critical assemblies such as laser cavity mounts, bimetal strips, and MEMS packaging.

(3) Adjustable expansion via cold work and heat treatment – Cold deformation further reduces the thermal expansion coefficient of 4J36 strip and wire, while controlled heat treatment stabilizes it for long‑term reliability.

(4) Good corrosion resistance in dry air – 4J36 forging and plate resist rust at room temperature in dry atmospheres, though protective measures are recommended for humid or harsh environments.

(5) Versatile product forms – Available as sheet, plate, bar, wire, strip, forging, and tube per GB/T or ASTM B753 (Invar 36), suitable for aerospace, cryogenic, and electronic applications.

Applications

4J36 iron-nickel alloy is used in environments that require extremely low expansion coefficients. Typical applications are as follows:

(1) LNG storage and transportation – 4J36 seamless tube and plate are used for liquefied natural gas tanks, pipelines, and membrane containment systems requiring minimal thermal contraction.

(2) Precision measurement and control instruments – 4J36 round bar and strip serve in temperature regulating devices, laser mounts, and optical frames operating below +200°C.

(3) Aerospace composite tooling – 4J36 forging and plate provide dimensionally stable molds for curing carbon fiber reinforced polymer (CRP) parts in aviation.

(4) Bimetal thermostats and shadow masks – 4J36 sheet and strip are laminated with higher‑expansion alloys for thermal switches and used as shadow masks for OLED/TV displays.

(5) Cryogenic and space components – 4J36 wire and tube are specified for electronic control unit frameworks in satellites and missiles operating below -200°C.

(6) Electromagnetic lens auxiliary tubes – 4J36 alloy is applied in laser control devices and electron beam focusing systems where low expansion ensures stable alignment.

MONO Group is one of Superalloy, Nickel alloy, high Temperature alloy manufacturer&Supplier&Wholesaler from China,We can supply high quality alloy plate,sheet,round bar,tube.pipes,fittings,flange,and custom parts in accordance with ASTM, ASME, DIN, ISO, GB, and other international standards. For inquiries or to request a quote , please freely contact us at info@monokj.com.