Nickel-iron alloy with a coefficient of thermal expansion approximately one-tenth that of carbon steel.
Maintains exceptional dimensional stability from cryogenic temperatures up to 500°F (260°C).
Retains good strength, toughness, and ductility even at cryogenic temperatures.
Available in multiple forms including bar, sheet, plate, wire, tube, and welding wire
Invar 36 (UNS K93600/K93603, Wnr 1.3912) is a solid-solution alloy that exhibits a uniquely low expansion rate across a broad temperature spectrum . The alloy’s thermal expansion coefficient ranges from approximately 1.1 × 10⁻⁶ /°C at 20-50°C to 2.5 × 10⁻⁶ /°C at 20-200°C, with minimal dimensional change up to the Curie temperature of 279°C (534°F) . It demonstrates good weldability using compatible filler metals and can be effectively hot and cold formed using standard processes similar to austenitic stainless steels . Typical applications include precision measuring instruments, aerospace composite tooling, laser and optical systems, cryogenic components, and standards of length . Full material traceability and mill test certificates (EN 10204 Type 3.1) are provided upon request
Chemical Composition
| Element | Content (%) | Notes |
|---|---|---|
| Nickel (Ni) | 35.0 – 37.0 | Primary alloying element |
| Iron (Fe) | Balance | Remainder |
| Carbon (C) | 0.05 – 0.10 max | Low carbon for weldability |
| Manganese (Mn) | 0.06 – 0.60 | Varies by specification |
| Silicon (Si) | 0.20 – 0.35 max | |
| Phosphorus (P) | 0.020 – 0.025 max | |
| Sulfur (S) | 0.002 – 0.025 max | |
| Chromium (Cr) | 0.15 – 0.50 max | |
| Cobalt (Co) | 0.50 – 1.0 max | |
| Molybdenum (Mo) | 0.50 max |
Mechanical Properties (Annealed Condition)
| Property | Typical Value |
|---|---|
| Tensile Strength | 430 – 490 MPa (63,000 – 71,000 psi) |
| Yield Strength (0.2% Offset) | 240 – 280 MPa (35,000 – 40,000 psi) |
| Elongation | 30 – 42% |
| Hardness | 70 – 135 HB / Rockwell B 70-90 |
| Reduction of Area | 65% |
Available Forms & Specifications
| Product Form | Size Range | Standards |
|---|---|---|
| Bar & Rod | 3mm – 280mm diameter | ASTM F1684, MIL-S-16598 |
| Sheet & Strip | 0.1mm – 5mm thickness | ASTM B753, DIN 1715 |
| Plate | 4mm – 130mm thickness | ASTM F1684 |
| Wire | 0.025mm – 21mm diameter | ASTM F1684 |
| Tube | OD 0.25mm – 25.4mm | Custom tolerances available |
| Foil | 0.005mm – 0.05mm thickness | Electrochemical deposition process |
Specifications & Designations
| Standard | Designation |
|---|---|
| UNS | K93600, K93601, K93603 |
| Wnr(Germany) | 1.3912 |
| ASTM | F1684, B388, B753 |
| DIN | 1715 (Sheet and Strip) |
| MIL Spec | MIL-S-16598, MIL-I-23011 CL 7 |
| AFNOR | NF A54-301 |
| Other Designations | FeNi36, Nilo 36, Alloy 36, 4J36, Nilvar, Pernifer 36 |
Applications
| Industry | Applications |
|---|---|
| Aerospace | Composite forming tools and dies, aircraft controls |
| Precision Instrumentation | Standards of length, measuring devices, gauges, calipers |
| Optics & Lasers | Laser components, optical systems, telescope components |
| Cryogenics | Tanks and piping for liquefied gas storage and transportation |
| Electronics | Radio and electronic devices, antenna supports |
| Telecommunications | Stable signal transmission components, sensor elements |
| Automotive | Thermostat rods, bimetal strips |
| Scientific | Pendulum rods for precision clocks, chronometers |
Frequently Asked Questions
Q: What is Invar 36 used for?
A: Invar 36 is used in applications requiring exceptional dimensional stability across temperature variations, including precision instruments, aerospace composite tooling, optical systems, cryogenic components, and standards of length .
Q: What is the coefficient of thermal expansion for Invar 36?
A: The coefficient is approximately 1.1 – 1.4 × 10⁻⁶ /°C from 20-100°C, about one-tenth that of carbon steel .
Q: What is the maximum operating temperature for Invar 36?
A: The alloy maintains its low expansion properties up to approximately 500°F (260°C). Above the Curie temperature of 279°C (534°F), expansion increases significantly .
Q: Can Invar 36 be welded?
A: Yes, Invar 36 exhibits good weldability using GTAW/TIG and GMAW/MIG processes with compatible filler metal CF36 .
Q: Is Invar 36 magnetic?
A: Yes, Invar 36 is ferromagnetic at room temperature up to its Curie temperature of approximately 279°C (534°F)
