Low-expansion alloys explained: Invar 36, Super Invar, Kovar, Alloy 42
Four iron-nickel alloys are quoted under the Invar name, and they are not interchangeable. Invar 36 holds about 1.3 ppm/°C near room temperature. Super Invar drops to about 0.5 ppm/°C over a narrower band. Kovar sits near 5 ppm/°C so that it matches borosilicate glass and alumina. Alloy 42 is the lead frame and bimetal alloy at 4 to 6 ppm/°C.
These guides explain what each alloy does across temperature, which specification governs it, how it is bought and what happens to its expansion when it is cut, welded, cast or aged. Values are typical handbook figures. The mill certificate for your heat lot is the number to design to.
34 guides in this section.
- Sep 26, 2026
Machining Alloy 42 (ASTM F30): Thin Parts, Flatness and Alloy Choice
Alloy 42 machining: ASTM F30, typical CTE 4 to 6 ppm/°C, used in lead frames and ceramic packages. Thin part fixturing, stamping vs machining and alloy choice.
- Sep 26, 2026
Where Aerospace Programs Use Invar 36 Tooling and Fixtures
Invar 36 assembly jigs, drill templates and test fixtures in aerospace: why fixture growth shows up as measurement error, and when the alloy's cost is worth it.
- Sep 26, 2026
How the CTE of Invar 36 Changes With Temperature and Condition
Invar 36 CTE vs temperature: typical 1.2 to 1.6 ppm/°C from 20 to 100 °C, rising past 150 °C and near plain steel above the Curie point. Tables and an example.
- Sep 26, 2026
Invar Parts for Diagnostic and Lab Equipment Manufacturers
Invar 36 machining for diagnostic imaging, lab automation and analyzer components, where dimensional stability protects calibration accuracy over temperature.
- Sep 26, 2026
Invar and Super Invar parts for wafer stages and reference frames
Invar semiconductor lithography parts explained: stage bodies, metrology frames, why sub-micron drift matters, cleanliness, magnetics near motors and RFQ notes.
- Sep 26, 2026
Invar Parts for Particle Accelerators and Beamlines
Why accelerator facilities specify Invar 36 and Super Invar for magnet mounts and alignment fixtures, and how beamline scale changes the machining and sourcing conversation.
- Sep 26, 2026
Invar Machining for Spectrometer and Analytical Instrument Manufacturers
Why spectrometer and analytical instrument makers specify Invar 36 for grating mounts and optical benches, how thermal drift becomes calibration error and what to put on the RFQ.
- Sep 26, 2026
Invar is ferromagnetic: what that changes in the shop and in service
Is Invar magnetic? Yes, Invar 36 and Kovar are ferromagnetic below their Curie points. What it means for magnetic chucks, demagnetizing, sensors and the RFQ.
- Sep 26, 2026
Machining Invar Reference Standards and Gauge Blocks
Invar reference standards for metrology labs: why the low CTE cuts temperature-driven uncertainty versus steel gauge blocks, and the tolerances a lab specifies.
- Sep 26, 2026
Invar Optical Bench Machining for Spacecraft Instruments
Why a spacecraft optical bench drawing differs from a ground telescope one: launch vibration survival, on-orbit vacuum and thermal cycling, and the verification tests that follow.
- Sep 26, 2026
Kovar Hermetic Packages for Defense and Avionics Electronics
Kovar housings, connector bodies and headers for defense and avionics electronics: production volume, qualification expectations and thermal cycling in service.
- Sep 26, 2026
Machining Kovar for Glass to Metal Seals: What the Seal Needs
Kovar glass to metal seal machining: why ASTM F15 Kovar matches borosilicate glass, how it machines, the anneal and oxide steps before sealing and the RFQ.
- Sep 26, 2026
Kovar Feedthroughs for Implantable Medical Electronics
How Kovar hermetic feedthroughs seal pins into implantable electronics, what to specify on the drawing and why certification stays the device maker's job.
- Sep 26, 2026
Kovar Machining for RF and Microwave Hermetic Connectors
Custom Kovar machining for RF hermetic connector bodies, pins and bulkhead feedthroughs: when catalog connectors do not fit and what to put on the RFQ.
- Sep 26, 2026
Kovar Hermetic Packages for Telecom Electronics Manufacturers
Machining Kovar lids, headers and butterfly packages for telecom optoelectronics: seam weld ledges, pin counts and when to machine versus stamp at volume.
- Sep 26, 2026
Choosing Invar, Kovar or Alloy 42 for RF and Microwave Housings
Decision guide for RF and microwave housing designers: matching Invar 36, Kovar or Alloy 42 to ceramic substrate CTE, sealing needs, cost and machinability.
- Sep 26, 2026
Super Invar Sourcing for Photonics and Laser Manufacturers
When a temperature-stabilized photonics enclosure justifies Super Invar over Invar 36, what availability and lead time actually look like, and what to check before you specify it.
- Sep 26, 2026
Super Invar Machining for Satellite Instrument Mounts
When a satellite payload's temperature-controlled band makes Super Invar worth the added cost and lead time over Invar 36, and the schedule risk that decision creates.
- Sep 26, 2026
Super Invar: The Lower CTE Option, Its Limits and How Shops Machine It
Super Invar machining: typical CTE 0.3 to 0.6 ppm/°C over a narrow band, the transformation risk below about -60 °C, the stabilization cycle and an example.
- Sep 26, 2026
Invar 36 vs Kovar vs Super Invar: Which Alloy for Your Part
Invar 36 vs Kovar vs Super Invar: typical CTE bands, Curie point, specs and machining notes, with a decision table for mounts, glass seals and space parts.
- Sep 21, 2026
Invar for Antenna and RF Waveguide Structures
Why some antenna reflectors, waveguide structures and RF reference frames specify Invar to hold electrical performance stable across temperature.
- Sep 21, 2026
Free-Machining Invar 36: What the Added Sulfur Changes
How free-machining Invar 36 differs from standard Invar 36, the tradeoff it makes for easier cutting, and which applications should avoid it.
- Sep 21, 2026
Obsolescence and Long Lead Times: Planning Invar Stock Orders Around Mill Minimums
Why Invar bar and plate lead times can stretch to weeks or months for nonstandard sizes, and how to plan orders and drawings around mill minimums and stock cycles.
- Sep 21, 2026
Invar 36 by Other Names: Regional Trade Names and Specs
Why the same 36 percent nickel-iron alloy is called Invar 36, Pernifer 36, Nilo 36 or FeNi36 depending on the supplier and region, and how to match specs across them.
- Sep 21, 2026
Invar vs ALLVAR Alloys: Comparing Low-Expansion Metal Options
How newer ALLVAR controlled-expansion alloys compare with Invar 36 and Super Invar, and when the difference actually matters for a machined part.
- Sep 20, 2026
Machining Invar Layup Molds and Mandrels for Composite Parts
Why Invar is used for carbon fiber layup tools instead of steel or aluminum, and what that means for machining large molds and mandrels to hold dimensions through autoclave cycles.
- Sep 20, 2026
Machining Invar for Cryogenic and Vacuum Applications
How Invar 36 behaves at cryogenic temperature and in vacuum service, and what that means for machined tolerances, cleaning and outgassing on parts destined for those environments.
- Sep 20, 2026
Long-Term Dimensional Stability: Does Invar Age After Machining?
Whether machined Invar parts keep moving over months or years after stress relief, and what shops do to minimize long-term dimensional drift beyond the initial process.
- Sep 26, 2026
Invar Machining: What Buyers Need to Know Before Sending a Drawing
How Invar machining differs from stainless: why shops rough, stress relieve then finish, which tolerances are realistic and what to put on your Invar 36 RFQ.
- Sep 20, 2026
Invar for Optical Benches and Telescope Structures: Why CTE Stability Matters
Why optical and telescope designers specify Invar 36 or Super Invar for mounts and structural benches, and what that means for how the parts are machined.
- Sep 20, 2026
Machining Super Invar and Invar 36 for Semiconductor Equipment
Why semiconductor and metrology equipment makers specify Invar and Super Invar for frames and reference plates, and what that means for tolerance, cleanliness and process control.
- Sep 20, 2026
Choosing Invar Stock: Bar vs Plate vs Sheet
How Invar 36 stock form affects lead time, cost and grain orientation, and which form fits round, block and thin-section parts best.
- Sep 20, 2026
Invar vs Zerodur and ULE Glass: Choosing a Low-Expansion Material
How machined Invar compares with Zerodur and ULE glass ceramics for low-expansion optical structures, and which applications favor a metal over a glass ceramic.
- Sep 20, 2026
Why Invar Work-Hardens and How Shops Control It During Machining
The mechanism behind work hardening in Invar 36, why it shows up as tool wear and poor finish, and the cutting practices shops use to keep it from taking over a job.
Other sections: Process, Cost, Choosing a Supplier.