INVAR 36 FM (Free-Machining) is a 36% nickel-iron alloy, but with a small addition of selenium to enhance machinability. This material has shown improved machinability for applications where high productivity is important. The free-machining alloy is advantageous to high-production shops when producing parts that have intricate shapes and/or require working to close tolerances. INVAR 36 is also known for its unique low expansion properties. The material has a rate of thermal expansion approximately one tenth that of carbon steel at temperatures up to 400 oF (204 oC). This characteristic makes the alloy ideal for products that require minimal dimensional change due to temperature variation and products where motion is desired when the temperature changes. INVAR 36 FM is used to produce electronic devices, aircraft controls, controls for hot water heaters, bimetallic thermostats, optical systems, and laser systems. (UNS K93050)
Free-Cut Invar 36 Alloy FM Mean Coefficient of Thermal Expansion |
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|---|---|---|---|
| Temperature 77°F to |
Coefficient x 10-6/°F |
Temperature 25°C to |
Coefficient x 10-6/°C |
| 212 | 0.91 | 100 | 1.64 |
| 302 | 1.32 | 150 | 2.38 |
| 392 | 1.69 | 200 | 3.04 |
| 482 | 2.34 | 250 | 4.21 |
| 572 | 3.26 | 300 | 5.87 |
Free-Cut Invar 36 Alloy FM Free-Cut Typical Physical Properties |
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|---|---|---|
| Density | lb/cu in | 0.291 |
| Specific Gravity | 8.05 | |
| Curie Temp | °F | 535 |
| °C | 280 | |
| Melting Point | °F | 2600 |
| Electrical Resistivity (70°F) | ohm-cir mil/ft | 495.0 |
| Thermal Conductivity | BTU-in/sq. ft-hr-°F | 72.6 |
| W/m °C | 10 | |
| Mean Specific Heat | BTU/lb-°F | 0.1230 |
Free-Cut Invar 36 Alloy FM Typical Mechanical Properties |
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|---|---|---|---|
| Annealed Bars | Cold Drawn Bars | ||
| Tensile Strength | ksi | 65 | 90 |
| MPa | 448 | 621 | |
| Yield Strength | ksi | 40 | 70 |
| MPa | 276 | 483 | |
| Reduction in Area | % | 65 | 60 |
| Elongation | % in 2″ | 35 | 20 |
| Hardness | Rockwell B | 70 | 90 |
| Modulus of Elasticity | ksi | 20.5 | 21.5 |
Free-Cut Invar 36 Alloy FM Free-Cut Chemistry |
|
|---|---|
| nominal % unless noted | |
| Iron | Bal |
| Nickel | 36.00 |
| Manganese | 0.90 |
| Silicon | 0.35 |
| Cobalt | 0.20 |
| Selenium | 0.20 |
Free-Cut Invar 36 Alloy FM Specifications |
|
|---|---|
| Free Machining Grade Round Bar, Rod | |
| ASTM F1684 | UNS K93050 |