Steel GX3Ni36
EN 1.3961
GX3Ni36 (1.3961) is a low-carbon Fe-36Ni casting grade of Invar, giving the low thermal expansion of wrought Invar 36 in shapes that cannot easily be machined from sheet or bar.
Reference datasheet — GX3Ni36 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the F condition
GX3Ni36 tempers and conditions
GX3Ni36 is supplied in 5 conditions, soft to hard. F 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 |
|---|---|---|---|---|---|---|
Solution annealed | Softest, most homogeneous condition; lowest and most reproducible expansion coefficient before final machining. | 205 | 425 | 30 | 120 HB | 2.2 % IACS |
Annealed, quenched, stress relieved 315 °C and stabilised 95 °C | Full metrology treatment: choose for gauges, masters and tooling that must hold dimensions for years. | 215 | 435 | 28 | 123 HB | 2.1 % IACS |
Hot isostatically pressed then annealed | Use for vacuum-tight or fatigue-critical castings where shrinkage porosity must be closed. | 225 | 470 | 35 | 125 HB | 2.1 % IACS |
Stress relieved | Pick when casting/weld residual stress must be cut before rough machining without changing strength much. | 235 | 445 | 27 | 128 HB | 2.1 % IACS |
FDefault As fabricated | Standard supply condition for rough castings that will be annealed/stabilised after rough machining. | 240 | 450 | 25 | 130 HB | 2.1 % IACS |
What is GX3Ni36?
GX3Ni36 (1.3961) is a low-carbon Fe-36Ni casting grade of Invar, giving the low thermal expansion of wrought Invar 36 in shapes that cannot easily be machined from sheet or bar. It is used for composite layup tooling, gauge bodies and mould bases, supplied as sand or investment castings in F, SR, A, A+ST and HIP+A conditions with about 240 MPa yield, 450 MPa tensile, 25 % elongation, 130 HB and service to 200 °C. The melt is sluggish and hot-tear sensitive, the alloy is gummy to machine and it is not corrosion resistant; GX5NiS36 is the free-machining alternative. GX3Ni36 has a density of 8.1 g/cm³ (0.293 lb/in³), heavier than 97% of steel grades. It melts at 1,425°C (2,597 °F). GX3Ni36 has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 96% of steel grades. Elongation at break is 25% and the elastic modulus is 140 GPa (20.3 Msi).
What is GX3Ni36 used for?
- Composite/CFRP layup tooling
- Precision measuring instrument castings
- Mold bases requiring dimensional stability
- Cryogenic component castings
Advantages
- Good corrosion resistance — 25/100, better than 92% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Low stiffness — 140 GPa (20.3 Msi), worse than 99% of steel grades
- Poor heat conductor — 11 W/m·K (6.36 BTU/hr·ft·°F), worse than 99% of steel grades
- Low electrical conductivity — 2.1 % IACS, worse than 99% of steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 99% of steel grades
- Low strength — 240 MPa (34.8 ksi), worse than 96% of steel grades
GX3Ni36 properties
Typical room-temperature values for GX3Ni36-F; bars are the position among steel grades.
Physical3
GX3Ni36 has a density of 8.1 g/cm³ (0.293 lb/in³), heavier than 97% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
GX3Ni36 has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 96% of steel grades. Elongation at break is 25% and the elastic modulus is 140 GPa (20.3 Msi).
Thermal6
GX3Ni36 is rated for continuous service to 200°C (392 °F). It conducts heat at 11 W/m·K (6.36 BTU/hr·ft·°F), worse than 99% of steel grades. Thermal expansion is 2.2 µm/m·K (1.22 µin/in·°F).
Electrical3
GX3Ni36 conducts electricity at 2.1 % IACS, worse than 99% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 92% of steel grades.
Sustainability4
Producing a kilogram of GX3Ni36 takes about 90 MJ of energy and emits 7 kg of CO₂ — more than 98% of steel grades. Typical recycled content is 45%.
Manufacturability8
GX3Ni36's machinability is poor (30/100, worse than 89% of steel grades); weldability good (58/100); formability poor (20/100).
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 steel family
Yield strength against density for every steel grade FabDigit runs. GX3Ni36 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with GX3Ni36
Is GX3Ni36 easy to machine?
Gummy and work-hardening: use sharp positive-rake carbide, heavy flood coolant, low speed (~25–40 m/min) and constant feed to avoid rubbing; rough-machine, anneal, then finish.
Can GX3Ni36 be welded?
GTAW/EBW with matching Fe-36Ni filler, low heat input and clean joints; avoid sulphur/lead contamination (hot cracking) and re-anneal welds to restore low CTE.
Can GX3Ni36 be formed, bent or molded?
Sand or investment cast with generous risering and controlled pouring — melt is sluggish, gas- and hot-tear-sensitive; allow ~2 % shrinkage and machining stock.
GX3Ni36 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 |
|---|---|---|
| CGX3 designation = ≈0.03 % C | ≤ 0.05 | 0.03 |
| Sideoxidiser, raises CTE if high | ≤ 0.5 | 0.3 |
| Mn | ≤ 0.6 | 0.35 |
| P | ≤ 0.03 | |
| S | ≤ 0.02 | |
| NiInvar composition; CTE minimum near 36 % Ni | 35 – 37 | 36 |
| Crresidual | ≤ 0.5 | |
| Coresidual; deliberate Co additions give Super-Invar variants | ≤ 0.5 | |
| Fe | balance |
What surface finishes work on GX3Ni36?
Polishes well for mould faces; corrosion protection by electroless nickel, chrome plating, paint or oiling — no anodising (ferrous).
Surface treatments FabDigit runs on steel 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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel GX3Ni36 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- 1.3961
- Also called
- Cast Invar 36
How much does GX3Ni36 cost?
GX3Ni36 is a high-cost steel ($$$$), pricier than about 78% 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.
GX3Ni36 — frequently asked
What is GX3Ni36 used for?
GX3Ni36 is typically used for composite/CFRP layup tooling, precision measuring instrument castings, mold bases requiring dimensional stability and cryogenic component castings. In short: cast Invar for tooling; weldable low-expansion casting; tough cast Fe-36Ni.
What is the yield strength of GX3Ni36?
GX3Ni36 has a typical yield strength of 240 MPa (34.8 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 96% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is GX3Ni36 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Gummy and work-hardening: use sharp positive-rake carbide, heavy flood coolant, low speed (~25–40 m/min) and constant feed to avoid rubbing; rough-machine, anneal, then finish.
Can GX3Ni36 be welded?
Yes — weldability is rated good (58/100). GTAW/EBW with matching Fe-36Ni filler, low heat input and clean joints; avoid sulphur/lead contamination (hot cracking) and re-anneal welds to restore low CTE.
What surface finishes work on GX3Ni36?
Polishes well for mould faces; corrosion protection by electroless nickel, chrome plating, paint or oiling — no anodising (ferrous).
Can GX3Ni36 be formed, bent or molded?
Sand or investment cast with generous risering and controlled pouring — melt is sluggish, gas- and hot-tear-sensitive; allow ~2 % shrinkage and machining stock.
What is the maximum service temperature of GX3Ni36?
GX3Ni36 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between GX3Ni36-F and GX3Ni36-A?
F is the default condition — standard supply condition for rough castings that will be annealed/stabilised after rough machining. A: softest, most homogeneous condition; lowest and most reproducible expansion coefficient before final machining. Yield strength is 240 MPa in F versus 205 MPa in A.
How much does GX3Ni36 cost?
GX3Ni36 is a high-cost steel ($$$$), pricier than about 78% 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.
Sources
- DIN 17745 — Wrought and cast alloys of iron and nickel with defined physical properties — DIN (2002)
- ASM Specialty Handbook: Nickel, Cobalt and Their Alloys (low-expansion Fe-Ni alloys) — ASM International (2000)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- Invar 36 / Pernifer 36 alloy datasheets (cast and wrought) — VDM Metals / Aperam / Carpenter (2021)
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.