Nickel Alloy Invar 36
UNS K93600 · EN 1.3912 · also Invar
Invar 36 is an Fe-36Ni soft-magnetic low-expansion alloy whose coefficient of thermal expansion is about 1.2 µm/m·K from room temperature to roughly 200 °C.
Values for the O condition
Invar 36 tempers and conditions
Invar 36 is supplied in 5 conditions, soft to hard. O is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ODefault Annealed | Standard stocked condition for plate, sheet, bar and forgings; maximum ductility and lowest, most reproducible CTE. | 280 | 490 | 40 | 135 HB | — |
Hot rolled | Heavy plate, billet and forgings supplied as hot-worked; machine oversize and anneal before final dimensional work. | 300 | 500 | 35 | 150 HB | 2.1 % IACS |
Stress relieved | Post-machining cycle (≈830 °C anneal, 315–370 °C stress relief, then long low-temperature age) for gauge blocks and metrology parts needing minimal long-term dimensional drift. | 380 | 520 | 28 | 160 HB | 2.1 % IACS |
Cold drawn | Bar, tube and strip cold worked ~20–30 % for higher strength and better surface/size tolerance; CTE slightly raised until stabilized. | 560 | 700 | 15 | 20 HRC | — |
Hardened | Choose for low-expansion springs, diaphragms and fine wire where maximum strength matters more than ductility. | 830 | 950 | 5 | 30 HRC | 2 % IACS |
What is Invar 36?
Invar 36 is an Fe-36Ni soft-magnetic low-expansion alloy whose coefficient of thermal expansion is about 1.2 µm/m·K from room temperature to roughly 200 °C. It is standard for metrology frames, optical structures, composite tooling and cryogenic LNG containment, and annealed stock gives 280 MPa yield, 490 MPa tensile, 40% elongation and 135 HB with good weldability and cryogenic toughness. Above the Curie point near 279 °C the Invar effect is lost and the service limit on file is 230 °C; thermal conductivity is low and machining is gummy. Corrosion resistance is only comparable to low-alloy steel, so plating or paint is normally required — use Kovar for glass-sealing parts. Invar 36 has a density of 8.1 g/cm³ (0.293 lb/in³), lighter than 80% of nickel alloy grades. It melts at 1,427°C (2,601 °F). Invar 36 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 82% of nickel alloy grades. Elongation at break is 40% and the elastic modulus is 141 GPa (20.5 Msi).
What is Invar 36 used for?
- Cryogenic LNG tank membranes and piping
- Metrology frames and gauge fixtures
- Optical benches and telescope structures
- Composite layup tooling and moulds
- Laser and photonics mounts
- Precision instrument shadow masks
- Satellite structural components
Advantages
- Low embodied carbon — 6.5 kg CO₂/kg, better than 99% of nickel alloy grades
- Forms and bends easily — 80/100, better than 91% of nickel alloy grades
- Easy to machine — 30/100, better than 90% of nickel alloy grades
- High electrical conductivity — 2.1 % IACS, better than 82% of nickel alloy grades
Limitations
- Limited service temperature — 230°C (446 °F), worse than 99% of nickel alloy grades
- Needs corrosion protection — 32/100, worse than 98% of nickel alloy grades
- Low stiffness — 141 GPa (20.5 Msi), worse than 97% of nickel alloy grades
- Low strength — 280 MPa (40.6 ksi), worse than 82% of nickel alloy grades
Invar 36 properties
Typical room-temperature values for Invar 36-O; bars are the position among nickel alloy grades.
Physical3
Invar 36 has a density of 8.1 g/cm³ (0.293 lb/in³), lighter than 80% of nickel alloy grades. It melts at 1,427°C (2,601 °F).
Mechanical14
Invar 36 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 82% of nickel alloy grades. Elongation at break is 40% and the elastic modulus is 141 GPa (20.5 Msi).
Thermal6
Invar 36 is rated for continuous service to 230°C (446 °F). It conducts heat at 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 73% of nickel alloy grades. Thermal expansion is 1.3 µm/m·K (0.722 µin/in·°F).
Electrical3
Invar 36 conducts electricity at 2.1 % IACS, better than 82% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (32/100), worse than 98% of nickel alloy grades.
Sustainability4
Producing a kilogram of Invar 36 takes about 90 MJ of energy and emits 6.5 kg of CO₂ — less than 99% of nickel alloy grades. Typical recycled content is 30%.
Manufacturability8
Invar 36's machinability is poor (30/100, better than 90% of nickel alloy grades); weldability very good (70/100); formability very good (80/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the nickel alloy family
Yield strength against density for every nickel alloy grade FabDigit runs. Invar 36 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Invar 36
Is Invar 36 easy to machine?
Gummy and work-hardening: use rigid setups, sharp positive-rake carbide, heavy positive feed, low-to-moderate speed (~20–40 m/min) and flood coolant; never dwell in the cut.
Can Invar 36 be welded?
Readily joined by GTAW, EBW and laser with matching Invar 36 filler; keep heat input and interpass temperature low, use clean joints to avoid hot cracking and porosity from S/P pickup.
Can Invar 36 be formed, bent or molded?
Annealed sheet deep-draws, spins and bends well; heavy cold work raises CTE, so a re-anneal plus stabilization cycle is required for precision low-expansion parts.
Manufacturability
The process limits FabDigit's quote engine applies to Invar 36. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Fair30 / 100 |
|---|---|
| ISO material group | S.1 |
| Cutting speed (rough / finish) | 40 / 55 m/min |
| Minimum wall | 1.5 mm |
| Minimum internal radius | 2 mm |
| Drill depth limit | 3× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better80 / 100 |
|---|---|
| Weldability | Good70 / 100 |
| Bendable | Yes |
Invar 36 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Nicontrols the invar effect; ±0.2 % shifts CTE noticeably | 35 – 37 | 36 |
| C | ≤ 0.1 | 0.03 |
| Mn | ≤ 0.6 | 0.35 |
| Si | ≤ 0.4 | 0.2 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Coresidual | ≤ 0.5 | |
| Crresidual | ≤ 0.25 | |
| Febalance ≈63–64 % | balance |
What surface finishes work on Invar 36?
Not anodizable — protect with electroless nickel, chrome plate, black oxide or paint; takes a fine optical polish before plating for mirror and metrology structures.
Surface treatments FabDigit runs on nickel alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Equivalent designations
Standards and trade names that resolve to Nickel Alloy Invar 36 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- K93600
- EN / DIN / Werkstoff-Nr.
- 1.3912
- Trade names
- Invar
- Other
- F1684B7534J36NILO36
How much does Invar 36 cost?
Invar 36 is a premium-cost nickel alloy ($$$), pricier than about 57% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Invar 36 — frequently asked
What is Invar 36 used for?
Invar 36 is typically used for cryogenic LNG tank membranes and piping, metrology frames and gauge fixtures, optical benches and telescope structures, composite layup tooling and moulds, laser and photonics mounts and precision instrument shadow masks. In short: low-expansion precision alloy.
What is the yield strength of Invar 36?
Invar 36 has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 82% of nickel alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Invar 36 easy to machine?
Not especially — machinability is rated poor (30/100, better than 90% of nickel alloy grades). Gummy and work-hardening: use rigid setups, sharp positive-rake carbide, heavy positive feed, low-to-moderate speed (~20–40 m/min) and flood coolant; never dwell in the cut.
Can Invar 36 be welded?
Yes — weldability is rated very good (70/100). Readily joined by GTAW, EBW and laser with matching Invar 36 filler; keep heat input and interpass temperature low, use clean joints to avoid hot cracking and porosity from S/P pickup.
What surface finishes work on Invar 36?
Not anodizable — protect with electroless nickel, chrome plate, black oxide or paint; takes a fine optical polish before plating for mirror and metrology structures.
Can Invar 36 be formed, bent or molded?
Annealed sheet deep-draws, spins and bends well; heavy cold work raises CTE, so a re-anneal plus stabilization cycle is required for precision low-expansion parts.
What is the maximum service temperature of Invar 36?
Invar 36 is rated for continuous use to about 230°C (446 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Invar 36-O and Invar 36-H?
O is the default condition — standard stocked condition for plate, sheet, bar and forgings; maximum ductility and lowest, most reproducible CTE. H: choose for low-expansion springs, diaphragms and fine wire where maximum strength matters more than ductility. Yield strength is 280 MPa in O versus 830 MPa in H.
How much does Invar 36 cost?
Invar 36 is a premium-cost nickel alloy ($$$), pricier than about 57% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in Invar 36?
Yes — Invar 36 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM F1684 — Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications — ASTM International (2021)
- GB/T 15018 / YB/T 5241 4J36 (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- Invar 36 / Nilo 36 alloy datasheet — Carpenter Technology / Special Metals / Ed Fagan (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.