Why Choose Invar 36

• Ultra-Low Thermal Expansion

  Invar 36 (36% nickel-iron alloy) has a coefficient of thermal expansion (CTE) of approximately 1.2 ppm/°C — compared to 12 ppm/°C for carbon steel and 23 ppm/°C for aluminum. A 500 mm Invar 36 component changes dimension by only 0.6 μm per °C of temperature change. For precision assemblies where temperature variation causes unacceptable dimensional drift, Invar 36 is the engineering answer.

• Dimensional Stability Over Temperature Range

  Invar 36 maintains its low CTE from cryogenic temperatures (down to -200°C) to its Curie point at approximately 230°C. Above 230°C, the CTE rises significantly — this defines the maximum service temperature for CTE-critical applications.

• Long-Term Stability

  Properly processed and stress-relieved Invar 36 maintains dimensional stability over time — important for precision masters, gauge blocks, and calibration references that must hold their dimensions over years of use.

Invar 36 Material Specifications

• Invar 36

  Available as bar, plate, sheet, and rod. The most widely available form for precision machining.

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• Our Machining Capability

  Invar 36 is a tough, gummy material that requires sharp tooling, appropriate cutting parameters, and — critically — stress relief before and after machining to achieve dimensional stability. We machine Invar 36 with high-speed steel or uncoated carbide tooling (coated tools tend to adhere), flood coolant, and light finishing cuts to avoid introducing machining-induced residual stress. Stress relief heat treatment after rough machining and before final finishing is standard practice for precision Invar 36 work. 

• Limitations & Cost Considerations

  Invar 36 is expensive — raw material cost is significantly higher than carbon steel or stainless steel, and machining is challenging due to its tendency to work-harden and produce built-up edge on tooling. It is also prone to dimensional change if residual stress is not properly managed through heat treatment and machining sequence. Invar 36 should only be specified when thermal expansion is genuinely the design-critical property — for applications where only moderate thermal stability is required, tool steel or stainless steel with proper temperature compensation may be more economical.