Invar 36 Plates | UNS K93600 | FeNi36 | ASTM F1684 | Alloy 36

ATI Invar 36UNS K93600 · FeNi36 · ASTM F1684 · Alloy 36

Invar 36 is a 36% nickel-iron alloy with the lowest thermal expansion of virtually any metal near room temperature — it barely changes dimension as temperature shifts. E Steel is one of the few suppliers holding it in ready stock in Southeast Asia, cut to size, no minimum order, with a mill certificate on every order.

≈1.2×10⁻⁶/°C CTE (20–100°C)

~1/10expansion vs carbon steel

279°CCurie limit

36%nickel content

Ready stock · ASEAN — rare

No MOQ · order 1 piece

Cut to size · fine cut

Mill cert · supplied

What Invar 36 Is

Invar 36 (also called FeNi36, Alloy 36, Nilo 36 or Pernifer 36) is a controlled-expansion alloy discovered in 1896 — the work that earned Charles-Édouard Guillaume the 1920 Nobel Prize in Physics. Its near-zero thermal expansion comes from the "Invar effect": below the alloy's Curie temperature, a magnetic volume contraction offsets normal thermal expansion, so the metal holds its dimensions across a wide temperature swing.

This makes Invar 36 the default choice wherever a part must not move with temperature — composite layup tooling, cryogenic containment, and precision instruments. One caveat every buyer should note: Invar 36 is not a stainless steel. It resists corrosion in dry air but can rust in humid or aggressive conditions, so it is typically coated or kept in controlled environments.

Material SpecificationDesignationsInvar 36 · UNS K93600 · FeNi36 · Alloy 36 · Nilo 36 · Pernifer 36 · 4J36StandardsASTM F1684 · ASTM B388 · DIN 1.3912TypeControlled-expansion nickel-iron alloyNominal compositionNi 36% · balance FeCoefficient of thermal expansion≈1.2 ×10⁻⁶/°C (20–100°C){{ confirm vs cert }}Curie temperature279 °C (low-expansion holds below this)Density≈8.05 g/cm³Melting point≈1427 °CCorrosion resistanceNot stainless — may rust in humid conditionsAvailable formsPlate — cut to size {{ add sheet/bar if stocked }}Thickness range{{ confirm stocked range }}Minimum orderNone — single piece acceptedDocumentationMill certificate & traceability supplied

Where Invar 36 Is Used

• Aerospace composite toolingLayup molds for carbon-fibre parts that must hold dimension through cure
• Cryogenic containmentLNG membrane tanks and cold-service structures
• Precision metrologyGauges, standards, length bars, measuring instruments
• Optics & photonicsLaser benches, telescope structures, optical mounts
• Semiconductor & electronicsLead frames, dimensionally stable fixtures
• Scientific instrumentsRing laser gyroscopes, seismic and timing devices

Stock & Quote

Importing Invar 36 into ASEAN normally means long lead times and high minimums. E Steel holds it in ready stock — tell us the grade and dimensions and we'll confirm availability, cut to size, and supply the mill certificate. No minimum order.

Frequently Asked Question

What is Invar 36 and why does it have such low thermal expansion?

Invar 36 is an alloy of 36 percent nickel and balance iron. Below its Curie temperature its magnetic behaviour counteracts normal thermal expansion, an effect known as the Invar effect, giving it a coefficient of thermal expansion near 1.2 ×10⁻⁶ per degree Celsius — roughly one-tenth that of carbon steel.

What is the coefficient of thermal expansion of Invar 36?

The coefficient of thermal expansion of Invar 36 is approximately 1.2 ×10⁻⁶ per degree Celsius between 20 and 100 degrees Celsius, rising toward roughly 2.0 ×10⁻⁶ over wider ranges. The exact value depends on temperature range and temper and is stated on the mill certificate.

Up to what temperature does Invar 36 keep its low expansion?

Invar 36 keeps its low-expansion behaviour up to its Curie temperature of 279 degrees Celsius. Above that point the alloy becomes paramagnetic and its thermal expansion rises to normal metallic levels, so designs relying on dimensional stability should stay below the Curie point.

Does Invar 36 rust or resist corrosion?

Invar 36 is not a stainless steel and is not corrosion resistant. It stays stable in dry air at room temperature but can rust in humid or aggressive environments, so it is usually coated, plated or kept in controlled conditions when corrosion is a concern.

Does E Steel stock Invar 36 in Southeast Asia, and is there a minimum order?

Yes. E Steel is one of the few suppliers holding ready-stock Invar 36 plate in Southeast Asia, cut to size from its warehouse in Malaysia with no minimum order quantity and a mill certificate supplied with every order.