NAS 36 Forgings Invar 36 / Alloy 36 / FeNi36 · UNS K93600 · W.Nr. 1.3912
NAS 36 is an iron-nickel controlled expansion alloy containing 35.0 to 37.0 % nickel with iron as the balance. Its mean coefficient of thermal expansion between 20 °C and 100 °C is about 1.2 to 1.5 × 10-6 /K, roughly one tenth that of 18-8 stainless steel, so components hold their dimensions as temperature changes. NAS 36 is the Nippon Yakin designation for the alloy known generically as Invar 36 or Alloy 36, covered by UNS K93600 and W.Nr. 1.3912.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We produce NAS 36 as seamless rolled rings, forged flanges, discs, round bars, shafts, sleeves, bushings, tube sheets and hollow forged tubes, made to customer drawing and certified to EN 10204 3.1 or 3.2.
| Alloy type | Fe-36 % Ni controlled expansion alloy |
|---|---|
| Equivalents | Invar 36, Alloy 36, NILO 36, Pernifer 36, 4J36, FeNi36 |
| Designations | UNS K93600 / K93603, W.Nr. 1.3912, ASTM F1684 |
| Mean CTE 20-100 °C | 1.2 to 1.5 × 10-6 /K |
| Useful range | Cryogenic up to about 200-260 °C |
| Curie temperature | About 279 °C |
| Melting route | EAF + VOD, or ESR remelted |
| Forged forms | Rings, flanges, discs, bars, shafts, sleeves, tube sheets |
| Certification | EN 10204 3.1 or 3.2 (third party) |
| Supplier | Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China |
Material description
Most metals expand steadily on heating. NAS 36 does not, because it is ferromagnetic. Below the Curie temperature the magnetic ordering of the lattice produces a contraction that almost cancels normal thermal expansion. The effect only works while the alloy is magnetic, so the low expansion disappears above about 279 °C, and NAS 36 is always magnetic in the temperature range where it is used.
Two points follow for design and procurement. Heat treatment and cold work change the expansion coefficient: rapid cooling and cold working lower it, a later anneal raises it again, so the stabilising treatment belongs in the specification. And because the alloy is magnetic in service, it cannot be used where a non-magnetic material is required.
Chemical composition
| Element | Ni | C | Si | Mn | Cr | Co | Fe |
|---|---|---|---|---|---|---|---|
| min | 35.0 | – | – | – | – | – | bal. |
| max | 37.0 | 0.03 | 0.20 | 0.35 | 0.20 | 0.50 | bal. |
Limits above are the grade window we work to. Heat-specific analysis for your order appears on the EN 10204 certificate. Where an order is placed to ASTM F1684 (UNS K93600), the wider limits of that standard apply instead, so state the governing specification on the enquiry.
Mechanical properties
| Condition | Rm (MPa) | Rp0.2 (MPa) | A (%) | Hardness |
|---|---|---|---|---|
| Forged and annealed | 490 min | 270 min | 40 min | report |
Values are acceptance minima. Test location, orientation and specimen size are agreed per order and recorded on the certificate.
Physical and thermal properties
| Property | Typical value |
|---|---|
| Density | 8.1 g/cm³ |
| Melting point | 1427 °C |
| Curie temperature | 279 °C |
| Mean CTE, 20-100 °C | 1.2 to 1.5 × 10-6 /K |
| Modulus of elasticity | 145 GPa |
| Thermal conductivity | 10.5 W/(m·K) |
| Specific heat | 515 J/(kg·K) |
| Electrical resistivity | 0.80 µΩ·m |
| Magnetic behaviour | Ferromagnetic below the Curie point |
Typical published values for the Fe-36 % Ni alloy, given for design guidance. The expansion coefficient varies with heat treatment and cold work. We can measure it by dilatometry on your heat if the drawing calls out a target.
Forged forms and sizes
NAS 36 is normally sold as sheet and strip. Forged shapes are made to order from a dedicated ingot or billet. Every item below is produced to customer drawing.
| Forged form | Range |
|---|---|
| Seamless rolled rings | OD 200-3000 mm, height max 800 mm, wall min 30 mm |
| Forged flanges | ASME B16.5, B16.47, EN 1092-1, or to drawing |
| Forged discs and blanks | Dia. 100-1800 mm, thickness 30-600 mm |
| Round bars | Dia. 40-800 mm, length max 6000 mm |
| Shafts and spindles | Dia. 60-800 mm, length max 8000 mm |
| Sleeves and bushings | OD 100-1500 mm, ID min 60 mm |
| Tube sheets | Dia. max 2500 mm |
| Hollow forged tubes | OD 120-1200 mm |
| Piece weight | 5 kg to 20 t |
Manufacturing and inspection
- Melting. EAF plus VOD as standard. ESR remelting where cleanliness and segregation control matter, such as precision optical and metrology components.
- Forging. Open-die forging and ring rolling with a controlled reduction ratio, so grain flow follows the part contour instead of being cut through as in a part machined from plate.
- Heat treatment. Annealing followed by a stabilising treatment, typically 300 to 350 °C, to settle the expansion coefficient and relieve machining stress.
- Ultrasonic testing. EN 10228-3, SEP 1921 or ASTM A388, to the acceptance class specified.
- Mechanical and chemical testing. Tensile, hardness, grain size and chemical analysis. Dilatometric CTE measurement on request.
- Certification. EN 10204 3.1, or 3.2 witnessed by TUV, BV, SGS, DNV or Lloyd's Register.
Applications
LNG and cryogenic equipment
Flanges, tube sheets, rings and forged pipe components for liquefied gas storage, transfer lines and tanker containment. The alloy keeps its toughness and its dimensions down to cryogenic temperature.
Precision instruments and optics
Shafts, rings and frames for optical and laser benches, opto-electronic assemblies, metrology equipment and length standards that must not drift with ambient temperature.
Aerospace composite tooling
Forged discs, blanks and mould frames for autoclave-cured carbon fibre tooling. The tool expands with the composite rather than with the steel structure around it.
Temperature control devices
Bimetal thermostat elements, thermostat rods and temperature regulators working below 200 °C, paired with a high expansion alloy to give controlled deflection.
Electronics and microwave
Cavity resonators, echo boxes and filters for mobile telephony, magnetic shielding, small transformer cores and specialised electronic housings.
Valve and pressure parts
Forged valve bodies, stems, seat rings and blocks, plus shells for pressure vessels, air receivers and shell and tube heat exchangers in low expansion service.
Related controlled expansion grades
| Grade | Nominal Ni | Curie point | Typical use |
|---|---|---|---|
| NAS 36 / Invar 36 | 36 % | 279 °C | Lowest expansion below about 200 °C |
| Invar 42 / Alloy 42 | 42 % | 350 °C | Hotter service, hard glass sealing |
| Alloy 46 | 46 % | 460 °C | Soft glass and ceramic seals |
| Alloy 52 | 50-52 % | 510 °C | Glass to metal seals at higher temperature |
| Kovar | 29 % Ni, 17 % Co | 435 °C | Hermetic seals to borosilicate glass and alumina |
Frequently asked questions
What is NAS 36?
NAS 36 is an iron-nickel controlled expansion alloy containing 35.0 to 37.0 % nickel with iron as the balance. Its mean coefficient of thermal expansion between 20 and 100 °C is about 1.2 to 1.5 × 10-6 /K, roughly one tenth that of 18-8 stainless steel, so parts hold their dimensions as temperature changes. NAS 36 is the Nippon Yakin designation for the alloy known generically as Invar 36 or Alloy 36, covered by UNS K93600.
Is NAS 36 the same as Invar 36?
Yes. NAS 36, Invar 36, Alloy 36, NILO 36, Pernifer 36, 4J36 and FeNi36 all describe the same nominal Fe-36 % Ni composition. NAS 36 is a Japanese brand name, Invar and NILO are trademarks, and UNS K93600, W.Nr. 1.3912 and ASTM F1684 are the neutral specification designations. Orders should be placed against the specification and acceptance criteria rather than the trade name.
What is the thermal expansion coefficient of NAS 36?
The mean coefficient of thermal expansion of NAS 36 is typically 1.2 to 1.5 × 10-6 /K over 20 to 100 °C. The value depends on heat treatment and cold work. Rapid cooling and cold working lower it, and a later anneal raises it again. If the design has a target CTE, state it on the enquiry so the forging can be given a stabilising heat treatment and the value verified by dilatometry.
Up to what temperature does NAS 36 stay dimensionally stable?
NAS 36 keeps its low expansion from cryogenic temperatures up to roughly 200 to 260 °C. Above the Curie temperature of about 279 °C the alloy loses its ferromagnetism and the expansion coefficient rises to normal levels, so it is not used as a low expansion material above that point. Alloy 42, Alloy 46 and Alloy 52 are the usual alternatives for hotter service.
Can NAS 36 be supplied as forged rings and flanges rather than sheet?
Yes. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory and produces NAS 36 as seamless rolled rings, forged flanges, discs and blanks, round bars, shafts, sleeves and bushings, tube sheets and hollow forged tubes, made to customer drawing. Sheet and strip are the usual commercial forms for this alloy, so forged shapes are made to order from a dedicated ingot or billet.
Which melting route is used for NAS 36 forgings?
NAS 36 is melted by EAF plus VOD, with ESR remelting where the application calls for higher cleanliness and tighter segregation control, such as precision optical and metrology parts. State the required melting route on the enquiry, because it affects both price and lead time.
What testing and certification do you supply with NAS 36 forgings?
Standard scope covers chemical analysis, tensile and hardness testing, grain size and, on request, dilatometric measurement of the expansion coefficient. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 as specified. Certificates are issued to EN 10204 3.1, or 3.2 with third party witness such as TUV, BV, SGS, DNV or Lloyd's Register.
Is NAS 36 magnetic?
Yes. NAS 36 is ferromagnetic below its Curie temperature of about 279 °C, and the magnetic ordering is what produces the low expansion. The alloy is therefore magnetic across the whole temperature range in which its low expansion behaviour is useful, and it is not suitable where a non-magnetic material is required.
Can NAS 36 be welded and machined?
NAS 36 welds by GTAW and GMAW using a matching Fe-36 % Ni filler, and it is machined much like austenitic stainless steel: slow speeds, positive rake, rigid setups and plenty of coolant, because the alloy is gummy and work hardens. For close dimensional tolerance, rough machine, stress relieve at 300 to 350 °C, then finish machine.
How do I request a quotation for NAS 36 forgings?
Send a drawing or the finished dimensions, quantity, governing specification and certificate level to sales@steelforgepieces.com, or call +86-189-2135-9659. Jiangyin Jiangnan Metal Co., Ltd. is at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Quotations are normally returned within 24 hours on working days.
Request a quotation
Send the drawing or the finished dimensions, the quantity, the governing specification and the certificate level required. Quotations are returned within 24 hours on working days.
- CompanyJiangyin Jiangnan Metal Co., Ltd., open-die forging factory
- AddressNo.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Phone+86-189-2135-9659
- Emailsales@steelforgepieces.com
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Jiangyin Jiangnan Metal Co., Ltd. Last updated .