Nickel Alloy Invar 36 · temper · default condition
Nickel Alloy Invar 36-O
Properties of the O condition, compared with the other Invar 36 tempers.
Standard stocked condition for plate, sheet, bar and forgings; maximum ductility and lowest, most reproducible CTE.
What is Invar 36-O?
Invar 36-O is Invar 36 in the O temper — standard stocked condition for plate, sheet, bar and forgings; maximum ductility and lowest, most reproducible CTE. Invar 36-O has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 81% of nickel alloy grades. Elongation at break is 40% and the elastic modulus is 141 GPa (20.5 Msi). Invar 36-O has a density of 8.1 g/cm³ (0.293 lb/in³), lighter than 78% of nickel alloy grades. It melts at 1,427°C (2,601 °F).
Advantages
- Low embodied carbon — 6.5 kg CO₂/kg, better than 99% of nickel alloy grades
- Forms and bends easily — 80/100, better than 90% of nickel alloy grades
- Easy to machine — 30/100, better than 89% 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 81% of nickel alloy grades
Invar 36-O properties
Typical room-temperature values for Invar 36-O — 12 properties are specific to this condition; the rest are grade-level values shared by every Invar 36 temper. Each bar shows where the value sits among the nickel alloy grades in FabDigit's library — further right is higher.
Physical3
Invar 36-O has a density of 8.1 g/cm³ (0.293 lb/in³), lighter than 78% of nickel alloy grades. It melts at 1,427°C (2,601 °F).
Mechanical14
Invar 36-O has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 81% of nickel alloy grades. Elongation at break is 40% and the elastic modulus is 141 GPa (20.5 Msi).
Thermal6
Invar 36-O 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-O 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-O 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-O's machinability is poor (30/100, better than 89% 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.
Other Invar 36 tempers and conditions
Invar 36 is also supplied in 4 other conditions. The full side-by-side table is on the Invar 36 overview.
- ODefaultStandard stocked condition for plate, sheet, bar and forgings; maximum ductility and lowest, most reproducible CTE.280 MPa yield · 135 HB
- HChoose for low-expansion springs, diaphragms and fine wire where maximum strength matters more than ductility.830 MPa yield · 30 HRC
- CDBar, tube and strip cold worked ~20–30 % for higher strength and better surface/size tolerance; CTE slightly raised until stabilized.560 MPa yield · 20 HRC
Working with Invar 36-O
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.
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.
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 | — |
Invar 36-O — frequently asked
What is Invar 36-O used for?
Invar 36-O 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-O?
Invar 36-O has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 81% of nickel alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Invar 36-O easy to machine?
Not especially — machinability is rated poor (30/100, better than 89% 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-O 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-O?
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-O 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-O?
Invar 36-O 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.
Can FabDigit make parts in Invar 36-O?
Yes — Invar 36-O 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.