Invar 36, UNS K93600, is a 36 percent nickel iron alloy with a coefficient of thermal expansion near zero across ambient temperature ranges. That dimensional stability is the entire reason it exists: it lets tooling, optics and instruments hold geometry while temperature moves.
Composite layup tooling is a major application, because the mould must match the low expansion of the cured composite through the autoclave cycle. Related grades cover other expansion targets: Super Invar 32-5 for the lowest expansion near room temperature, Invar 42 and 46 for glass and ceramic sealing, and Kovar for hermetic glass to metal seals.
Stocked as plate, sheet, bar and wire.
Sizes and stock
- Round bar: up to 6" DIA
- Sheet / plate: up to 5" THK
- Tube and custom shapes: per request
Processing capabilities
- Billet conversion and open die, closed die and ring forging
- Solution treat, age and anneal to the applicable spec
- Saw cutting, trepanning, gun drilling and CNC machining
- Ultrasonic, penetrant dye, micrography and physical testing
Specifications
Material is released to the applicable specification with mill test reports and, on request, independent lab verification.
Why engineers specify Invar 36
- Near zero thermal expansion around ambient temperature
- Essential for composite layup tooling and precision instruments
- Machinable and weldable with established practice
- Related controlled expansion grades available from one source
Nominal chemistry
Percent by weight, nominal composition per the governing specification. The mill test report for your heat is the controlling document.
Typical mechanical properties
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Annealed | ~71 ksi | ~40 ksi | ~30% | - |
Typical published values for reference only, not for design. Properties vary with section size, product form and processing. Order to the specification and condition your drawing requires.
Typical applications
- Composite layup and autoclave tooling
- Optical and laser benches
- Precision instruments and standards
- Cryogenic tankage and LNG membranes
Fabrication notes
Machining
Nickel and cobalt superalloys work harden aggressively. Use rigid setups, sharp tooling, slow speeds, positive feed that stays under the hardened skin, and flood coolant. Age hardened material machines far more slowly than solution treated material, so rough before aging wherever the print allows.
Welding
Most solid solution grades weld readily with matching filler. Age hardenable grades such as 718 and Waspaloy are welded in the solution treated condition and aged afterward to control strain age cracking.
Forming
Hot working ranges are narrow and forces are high. Cold form in the annealed condition with intermediate anneals, and stress relieve before final heat treatment.
Invar 36 compared with similar grades
Super Invar 32-5
Even lower expansion over a narrower temperature range.
Kovar
Expansion matched to borosilicate glass for hermetic seals.
Designations and cross reference
- Material family
- Nickel & Cobalt Alloys
- UNS number
- K93600
- Werkstoff (W.Nr)
- 1.3912
Working from an obsolete, foreign or superseded designation? Send it over and we will cross reference it to a current grade and specification.
Quality, testing and traceability
Supplied with mill test reports and heat traceability, with ultrasonic inspection, penetrant dye, micrography, grain size, stress rupture and mechanical testing available on request.
We are AS9100D and ISO 9001:2015 registered. If our stock does not already carry the inspection your specification requires, we can quote the material with that work performed. More on our quality system
Available forms
Custom sizes converted from billet, plus saw cut, waterjet and near-net blanks. See custom conversions
Invar 36 frequently asked questions
What is Invar 36?
Invar 36, UNS K93600, is a 36 percent nickel iron alloy with a coefficient of thermal expansion near zero across ambient temperature ranges. That dimensional stability is the entire reason it exists: it lets tooling, optics and instruments hold geometry while temperature moves.
What forms is Invar 36 available in?
We supply Invar 36 in bar, sheet, plate, tube. Custom sizes are converted from billet, and we can provide saw cut, waterjet or near net blanks so material arrives closer to your finished part.
What is the UNS or equivalent designation for Invar 36?
Invar 36 is designated UNS K93600, Werkstoff 1.3912. If your drawing calls out an obsolete or foreign designation we can cross reference it and confirm the equivalent before you order.
What specifications can Invar 36 be supplied to?
Commonly ordered specifications include ASTM B753 Alloy T36, ASTM-F1684-06, AMS-I-23011. Material is released to the specification and condition on your purchase order, with mill test reports supplied as standard.
What conditions can Invar 36 be ordered in?
We can supply Annealed. If our stock is not already in the condition you need, we can quote it with the heat treatment performed before shipment.
Can you cut Invar 36 to size?
Yes. Saw cutting, waterjet, laser and shearing are available, along with trepanning, gun drilling, lathe turning and CNC machining, so you can order blanks or rough machined pieces rather than full lengths.
Do you provide test reports and additional testing on Invar 36?
Every order ships with mill test reports and heat traceability. If your print calls for ultrasonic inspection, penetrant dye, magnetic particle, chemical assay, micrography, hardness or mechanical testing and our stock does not already carry it, we can quote the material with that work performed.
Can Invar 36 be supplied to DFARS domestic melt requirements?
Tell us at quote stage if the order is DFARS or domestic melt restricted and we will confirm availability against that requirement before you commit.
What do you need to quote Invar 36?
Grade, form, dimensions, quantity, specification and condition, plus any testing or certification requirements and the date you need it. Send a drawing if you have one. Quotes are typically ready within 24 hours.
How does Invar 36 compare with Super Invar 32-5?
Even lower expansion over a narrower temperature range.