Invar 36 Low-Expansion Alloy Sheet

Iron-Nickel Controlled-Expansion Alloy | Ultra-low Coefficient of Thermal Expansion | Fe-Ni36

Invar 36 (UNS K93600) is an iron-nickel low-expansion precision alloy containing approximately 36% nickel; it is also known as Nilo 36, FeNi36, 4J36, or simply Invar. Its most notable characteristic is an extremely low coefficient of thermal expansion-roughly one-tenth that of ordinary carbon steel-within the temperature range from ambient to approximately 260°C, allowing it to maintain near-constant dimensions despite temperature fluctuations.

Invar 36 plate is ideal for precision structural components sensitive to thermal deformation, such as precision instruments, optical equipment, laser systems, metrology standards, composite molding tools, electronic structural parts, and cryogenic equipment components. LorkGroup supplies Invar 36 plate, sheet, and precision-cut components tailored to customer specifications, with strict control over chemical composition, thickness, dimensional tolerances, heat treatment conditions, thermal expansion properties, and surface quality.

Invar 36 plates are primarily supplied in two delivery conditions: cold-rolled sheets (0.5–3.0 mm) typically feature a bright annealed (BA) or 2B smooth finish, while hot-rolled medium-to-heavy plates and forged blocks (4.0–150 mm) generally come with an alkali-pickled/acid-pickled, sandblasted, or rough-polished finish; cutting according to drawings is available for all types. The minimum order quantity (MOQ) is 50 kg, with a reference price range of $28–45/kg.

For reference, the official MTC from LorkGroup specifies the chemical composition in accordance with the actual procurement standards or technical agreements adopted.

The mechanical properties of Invar 36 sheet are influenced by sheet thickness, annealing conditions, amount of cold work, and grain structure.

If there are requirements regarding the coefficient of linear expansion during procurement, the temperature range, average coefficient of linear expansion, and test method must be specified.

For Invar 36 sheets, in addition to testing for chemical composition, mechanical properties, and thermal expansion characteristics, non-destructive testing is primarily employed to detect internal and surface defects-such as cracks, inclusions, delamination, lack of fusion, and voids-that could compromise subsequent precision machining and dimensional stability. LorkGroup primarily utilizes ultrasonic testing for the inspection of Invar 36 sheets.

 

 

Ultrasonic Testing (UT)

Ultrasonic pulse-echo testing is employed to inspect Invar 36 sheets for internal flaws. Ultrasonic waves are transmitted into the material via a probe, and echoes reflected from defects are captured to detect issues such as delamination, cracks, inclusions, voids, and other internal discontinuities.

 

Defects are evaluated against relevant inspection standards and customer technical requirements, considering their location, quantity, size, echo amplitude, and distribution, to determine whether the material's internal quality meets the specified acceptance criteria. The inspection results are compiled into a UT report that serves as the basis for product quality assessment and delivery acceptance.

Lork Group
Marketing Operations Department

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

Hot Tags: Invar 36, 4J36, UNS K93600, W.Nr. 1.3912, Fe-Ni36, ASTM F1684, YB/T 5241, low expansion alloy plate, controlled expansion alloy, Invar sheet