Material · Specialty Metals
Invar 36
The dimensional anchor: ~1.2 ppm/K expansion for parts that must not move with temperature.
Price index: $$$$
Material properties
| Parameter | Value |
|---|---|
| Tensile strength | ~485 MPa |
| Yield strength | ~240 MPa |
| Hardness | ~130–160 HB |
| Density | 8.05 g/cm³ |
Choose it when
When thermal drift is the enemy: optical cavities, metrology references and bonded composite tooling that must hold microns across temperature swings. Nothing common comes close to ~1.2 ppm/K.
Look elsewhere when
Expensive, heavy, gummy to machine (work-hardens like stainless) and only mildly corrosion-resistant — never a structural or general-purpose pick. If the part sees one temperature, MIC-6 or 316L is far cheaper.
Compatible finishes
As-Machined
The baseline finish: straight off the machine, fastest and cheapest.
Electroless Nickel Plating (ENP)
Plating without electricity: dead-uniform thickness everywhere, bores and threads included.
Polishing
Progressive abrasives down to mirror: the finish for optics, molds and show surfaces.
Laser Marking
Permanent identification with zero dimensional change: serials, logos and codes burned in, not stuck on.
Typical applications
- Optical mounts and laser benches
- Metrology frames and reference fixtures
- Composite layup tooling for aerospace
- Cryogenic and satellite instrument structures
Compared with similar grades
| Property | Invar 36 | Magnesium AZ31B |
|---|---|---|
| Tensile strength | ~485 MPa | ~260 MPa |
| Yield strength | ~240 MPa | ~170–200 MPa |
| Hardness | ~130–160 HB | ~49 HRB |
| Density | 8.05 g/cm³ | 1.77 g/cm³ |
| Price index | $$$$ | $$$ |
| Machinability | 2/5 | 5/5 |
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