Precision Alloys
Invar 36 / 4J36 (UNS K93600) — Composition, Properties & Supply
4J36 (Invar 36, UNS K93600) is a 36% nickel low-expansion iron-nickel alloy with a mean coefficient of thermal expansion of about 1.2×10⁻⁶/°C from −80 to +100 °C — roughly one tenth that of ordinary steel. It is used where dimensional stability is critical: precision instruments, LNG tanks and composite tooling.
What is the chemical composition of Invar 36 / 4J36?
| Element | Symbol | Content (wt%) |
|---|---|---|
| Fe | Fe | Balance |
| Ni | Ni | 35.0–37.0 |
| Co | Co | ≤ 0.50 |
| Mn | Mn | 0.20–0.60 |
| Si | Si | ≤ 0.30 |
| C | C | ≤ 0.05 |
| P | P | ≤ 0.020 |
| S | S | ≤ 0.020 |
Values are typical specification limits. Actual heat analysis is reported on the EN 10204 3.1 mill test certificate supplied with each shipment.
What are the mechanical properties of Invar 36 / 4J36?
| Property | Value | Note |
|---|---|---|
| Tensile strength | ≥ 440 MPa | Room temperature |
| Yield strength (0.2% offset) | ≥ 240 MPa | Room temperature |
| Elongation | ≥ 30 % | Gauge length 50 mm / 4D |
| Hardness | ≤ 170 HB | Brinell / Rockwell |
What are the physical properties of Invar 36 / 4J36?
| Property | Value |
|---|---|
| Density | 8.10 g/cm³ |
| Melting range | 1430–1450 °C |
| Thermal conductivity | 10.5 W/m·K |
| Elastic modulus | 141 GPa |
| Maximum service temperature | −80 ~ +100 ℃ (dimensional stability range) |
What are the key characteristics of Invar 36 / 4J36?
- CTE near room temperature of about 1.2×10⁻⁶/°C
- Outstanding dimensional stability for precision reference parts
- Most stable between −80 and +100 °C
- Retains good toughness at cryogenic temperatures (LNG)
Where is Invar 36 / 4J36 used?
- LNG carrier tanks and transfer piping
- Precision instruments, clocks and measurement standards
- Aerospace composite lay-up tooling
- Electronic packaging and lead frames
- Liquefied gas tank liners
Which standards and specifications cover Invar 36 / 4J36?
- ASTM F1684
- GB/T 14985
- UNS K93600
What product forms are available?
Frequently asked questions
Why is Invar 36's expansion so low?
This is the Invar effect: the 36% nickel iron-nickel alloy exhibits volume magnetostriction below its Curie temperature, so the normal lattice expansion with temperature is offset by magnetic contraction, giving very low net thermal expansion. Above the Curie point (about 230 °C) the CTE rises rapidly to that of ordinary steel.
Need Invar 36 / 4J36 bar, tube, plate or forgings?
Send the grade, dimensions, standard and quantity. We answer within 10 minutes on working days and quote within 24 hours, with EN 10204 3.1 certification.
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