Invar 36 Nickel Alloy Strip (UNS K93601, ASTM F1684)

Invar 36 strip is primarily supplied in thicknesses ranging from 0.2 mm to 2.0 mm and widths from 10 mm to 200 mm (custom dimensions are available); it can be provided either in cut-to-length pieces or in coils. Prices generally range from $60 to $80 per kilogram, depending on the supply condition and order quantity; please contact us to confirm the current price.

Invar 36 (also known as Invar alloy; corresponding to the Chinese grade 4J36) is an iron-nickel low-expansion precision alloy with a nickel content of approximately 36%. Its most distinctive characteristic is an extremely low coefficient of thermal expansion over a wide temperature range: between -60°C and +200°C, the average linear expansion coefficient is controlled within the range of 1.2×10⁻⁶/°C to 1.5×10⁻⁶/°C-roughly one-tenth that of ordinary carbon steel or austenitic stainless steel.

This "zero-expansion" property stems from the specific ratio of nickel (approximately 36%) to iron. At temperatures below the Curie point (approximately 230°C), the alloy is ferromagnetic; the magnetostrictive effect counteracts the thermal expansion caused by lattice thermal vibrations, resulting in virtually constant dimensions at the macroscopic level. Invar 36 strip offers a balance of moderate strength, toughness, and good workability, allowing it to be processed-via cold rolling, stamping, bending, and other methods-into thin strips and components with complex shapes.

Selection Note: For electronic-grade applications such as semiconductor equipment or optical communication modules, the use of ASTM F1684 Grade 2 material is recommended. If design specifications are based on the thermal expansion coefficient requirement of ≤1.2×10⁻⁶/°C from the YB/T 5241 standard, the equivalent expansion coefficient requirement must be stipulated in the contract when purchasing ASTM-standard materials.

Heat Treatment Sensitivity: The low-expansion characteristics of Invar 36 depend on proper heat treatment. Annealing temperatures exceeding 850°C cause rapid grain growth, leading to an increased coefficient of thermal expansion. Stress-relief annealing is required after cold working; otherwise, residual stresses may cause dimensional drift during service.

Machining Recommendations: Invar 36 produces sticky chips and is prone to built-up edge formation. Carbide tools are recommended, with cutting speeds maintained between 40 and 60 m/min and the use of ample coolant/lubricant.

Corrosion Protection: Invar 36 is susceptible to rusting in humid air; surface protection (such as nickel plating, chrome plating, or coating) is recommended for long-term use or outdoor applications.

Curie Temperature Limitation: Above approximately 230°C, the low-expansion properties are lost, and the coefficient of thermal expansion increases significantly to over 10 × 10⁻⁶/°C. Operating temperatures must remain below this threshold.

For more information, please contact:

Email: claire@lorkgroup.com
WhatsApp: +86 199 3707 5488

*Data based on the ASTM F1684 standard specification.

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