CNC Machining
Invar 36
Invar 36 (a 36% Nickel-Iron alloy) is engineered for absolute dimensional stability. With a coefficient of thermal expansion roughly one-tenth that of carbon steel, it is the ultimate material for precision optics, laser systems, and aerospace composite tooling where temperature fluctuations cannot compromise accuracy.
Core Mechanical Properties
While known for its near-zero thermal expansion, Invar 36 also offers solid structural integrity. Below is the typical mechanical data for annealed Invar 36 commonly used in CNC machining.
| Alloy Grade | Yield Strength | Tensile Strength | Hardness / CTE |
|---|---|---|---|
| Invar 36 (Annealed) | ~ 240 MPa | ~ 490 MPa | ~ 70 - 80 HRB |
| Thermal Expansion (CTE) | ~ 1.2 x 10-6 /°C (Between 20°C and 100°C) | ||
International Grade Comparison
Use our cross-reference chart to match American standards (UNS) with European (DIN/EN) and Chinese (GB) material equivalents for your Invar 36 requirements.
| UNS (USA) | DIN / EN (Europe) | GB (China) | Key Characteristics |
|---|---|---|---|
| K93600 (Invar 36) | 1.3912 / Ni36 | 4J36 | Contains 36% Nickel, balance Iron. Maintains exceptionally tight dimensional stability across typical ambient temperature fluctuations. |
| K93050 (Super Invar) | - | 4J32 | Contains Cobalt. Offers an even lower coefficient of thermal expansion than standard Invar 36 at room temperatures. |
Application Fit Matrix
Invar 36 is selected for dimensional stability across temperature changes in optical, metrology, aerospace tooling, and semiconductor equipment.
| Application | Recommended Material | Why This Material Works | Typical CNC Process | Finish / Risk Note |
|---|---|---|---|---|
| Optical Mounts & Lens Frames | Invar 36 | Very low thermal expansion helps maintain alignment. | Precision milling, boring, reaming | Stress relief is important before final finishing. |
| Metrology Frames & Datum Bars | Invar 36 | Stable geometry reduces measurement drift. | Milling, grinding, drilling | Plan roughing and finishing in stages. |
| Aerospace Composite Tooling | Invar 36 | CTE compatibility supports stable molds through thermal cycles. | Large-format milling, drilling | Simplify non-critical geometry to control cost. |
| Semiconductor Fixtures | Invar 36 | Low expansion preserves critical positioning. | Milling, tapping, pocketing | Cleanliness and burr control matter. |
| Scientific Instrument Parts | Invar 36 | Keeps mounts and references dimensionally predictable. | Milling, turning, lapping as needed | Do not over-specify cosmetic finish where stability is the goal. |
Selection Rule
Match the grade to the part's real job first: strength, heat, wear, corrosion, insulation, transparency, or cosmetic finish.
DFM Reminder
Material choice changes tolerance risk, burr control, wall thickness, thread strategy, and finishing route.
Quote Tip
Share the operating environment, mating parts, finish expectations, and inspection requirements with the drawing.
Expert Machining Tips
Invar 36 is highly ductile, gummy, and notoriously prone to rapid work hardening. Huade engineers apply stringent protocols to achieve tight tolerances:
- 1
Never Let the Tool Dwell
Because Invar 36 work-hardens rapidly, cutting tools must be kept constantly moving with a positive feed rate. Lingering or rubbing against the surface will instantly create a hardened glaze that destroys tool life.
- 2
Aggressive Chip Control
The high ductility of Invar produces long, stringy chips that can tangle around the spindle and mar the workpiece. We utilize tools with aggressive chip breakers and high-pressure coolant to force chip evacuation.
- 3
Rigid Setups & Sharp Tooling
We strictly employ sharp, positive-rake carbide tooling (often uncoated or TiAlN coated) mounted in highly rigid setups to cleanly shear the gummy alloy without inducing unnecessary cutting heat or deflection.
Top 3 Surface Treatments
Unlike stainless steel, Invar 36 contains no chromium and is prone to rusting in humid environments. Post-processing is vital for corrosion protection.
1. Electroless Nickel Plating
The standard finish for Invar. It deposits a highly uniform, corrosion-resistant protective layer over the part without altering the alloy's underlying low-expansion properties.
2. Passivation
While less common for rust prevention than nickel plating, chemical passivation cleans the surface of any free iron deposited during machining, ensuring maximum purity for sensitive optical applications.
3. Gold or Silver Plating
Applied primarily to Invar components used in high-frequency microwave, RF, and aerospace electronics where superior conductivity must be paired with zero thermal expansion.
Start Your Manufacturing RFQ
Upload your 3D CAD files today. Our engineering team will review your nickel-iron specifications and provide a free DFM report along with rapid pricing.