Controlled-expansion alloy · Iron-nickel · DIN designation

Ni36 Forgings: W.Nr. 1.3912 / FeNi36 / UNS K93600 / 4J36

Seamless rolled rings, flanges, round bars, discs, sleeves, tube sheets and shafts in the 36 % nickel controlled-expansion alloy. Open-die forged to your drawing in Jiangyin, China.

Technical datasheet · Published 18 May 2016 · Last reviewed 22 August 2026 · Compiled by the Jiangyin Jiangnan Metal Co., Ltd. metallurgical engineering team

CTE 20–93 °C

1.30µm/m·°C (10⁻⁶/°C)

Curie point

279 °C535 °F. The hard ceiling

Nickel

35–37 %balance iron

Density

8.05g/cm³ · 0.291 lb/in³

Melting point

1427 °C2600 °F

Tensile, min

490MPa · 71 ksi

Forging range

1090–1180°C, no soaking

Max ring OD

3000mm, seamless rolled

01What Ni36 is, and why its expansion coefficient is so low

Ni36 is a binary iron-nickel alloy, nominally 36 % nickel with the balance iron, that expands roughly one tenth as much as carbon steel when heated. Its mean coefficient of thermal expansion is about 1.30 µm/m·°C between 20 °C and 93 °C, against roughly 12 for plain carbon steel and 17 for 304 stainless. Nothing else about it is remarkable. It is not strong, it is not corrosion resistant, and it is not easy to machine. You buy it for one number.

The effect is magnetic, not structural. In the ferromagnetic state a magnetostrictive volume contraction runs opposite to ordinary lattice expansion and cancels most of it. Charles Édouard Guillaume identified this in 1897 and received the 1920 Nobel Prize in Physics for it. The cancellation weakens as temperature rises and disappears completely at the Curie point of 279 °C (535 °F), above which the alloy is paramagnetic and expands like any ordinary metal.

Two things follow from that, and both belong on the drawing rather than in the datasheet:

• The useful window is narrow. The coefficient starts climbing well before 279 °C is reached. If dimensional stability is the reason you selected the material, keep service temperature below about 200 °C and verify the mean coefficient over your interval rather than the headline 20–93 °C figure.
• Nickel content has to be held tightly. A drift of a few tenths of a percent away from 36 % moves the inversion temperature and raises the coefficient measurably. This is why the alloy is melted under close control, why cold work and residual stress matter, and why the mill certificate carries more weight here than on a structural grade.

02Is Ni36 the same as Invar 36?

Yes. Ni36 and Invar 36 are the same iron-nickel alloy at nominally 36 % nickel, balance iron. The two names come from different naming traditions, not different materials. Ni36 is the German DIN style, used alongside the Werkstoff number 1.3912. Invar is the original French trade name, from invariable. It is a registered trademark of Aperam Alloys Imphy, though it has passed into general engineering use. UNS K93600 is the brand-free American number, and 4J36 is the Chinese designation.

The names are not interchangeable on a purchase order, though. The standards behind them set slightly different composition limits, and that is where most procurement problems on this grade begin.

Jiangyin Jiangnan Metal accepts orders under any of these callouts and cross-lists the equivalents on the EN 10204 certificate. If your drawing carries the American designation and you want the data organised that way, our Invar 36 / ASTM F1684 forgings page covers the same alloy from the ASTM side.

03Ni36 designations, trade names and equivalents

Ni36 reaches a forging shop under at least fifteen different names, depending on which standards body wrote the drawing, which mill sold the material and which decade the specification dates from. Every designation below refers to the same nominal Fe-36Ni controlled-expansion chemistry.

04Chemical composition of Ni36: DIN, ASTM and GB side by side

The chemistry is deliberately simple. Nickel sets the expansion coefficient; everything else is held low because residual elements shift the expansion curve, coarsen the structure or interfere with hot working. Carbon in particular is capped because carbides distort the expansion behaviour and reduce the stability the alloy is bought for.

The comparison below is worth reading before you place an order. The three standards most often quoted for this alloy do not impose identical limits, and a heat that satisfies DIN 17745 will not necessarily satisfy ASTM F1684.

05Thermal expansion data: the number you are buying

Mean coefficient of thermal expansion measured from 20 °C to the stated temperature, on material annealed at 871 °C and furnace cooled. This is the dataset plotted at the top of this page.

What that means in a real part. A 2,000 mm Ni36 optical bench warming from 20 °C to 40 °C grows about 0.05 mm. The same bench in carbon steel grows about 0.47 mm, and in 304 stainless about 0.69 mm. On an instrument holding micron-level alignment, that difference is the reason the alloy exists, and the reason it costs what it does.

06Ni36 at cryogenic temperature, and why LNG uses it

Most datasheets stop at room temperature. A large share of the Ni36 forged in this factory goes into cold service, and below ambient the alloy does two useful things at once: it barely contracts, and it stays tough.

Cooling a Ni36 part from 20 °C to −196 °C shortens it by roughly 0.4 mm per metre, about 0.04 %. The same metre of 304 stainless loses about 3 mm. On a membrane tank hundreds of metres in girth, that adds up to metres of movement that the containment system would otherwise have to absorb in corrugations and expansion joints.

The second property matters as much as the first. Ni36 is face-centred cubic and does not undergo a ductile-to-brittle transition, so it keeps useful toughness all the way down. That combination of near-zero contraction and retained toughness is why the alloy became the standard membrane material for liquefied natural gas containment, and why it appears in cryogenic transfer lines, vessel internals and test rigs down to liquid nitrogen and below.

07Physical properties of Ni36

08Mechanical properties of Ni36 forgings

Ni36 behaves mechanically like a mild structural steel. It is not a strength alloy and nobody selects it for load capacity, but it is ductile, tough and readily formed. It retains good strength and toughness at cryogenic temperature, which is what qualifies it for LNG membrane containment and transfer lines down to −196 °C.

Cold work raises strength considerably, but it also raises the expansion coefficient and introduces residual stress that will relax later and move the part. For dimensionally critical work, forge, anneal and stabilise rather than cold work. If a drawing calls for both a tight CTE band and a high tensile strength, those two requirements conflict in this grade and the conflict has to be resolved before ordering, not during manufacture.

09Ni36 forms and sizes we forge

Everything below is made to order against a drawing or a dimension list. There is no standard catalogue. Open-die forging exists precisely so you do not have to design around stock sizes.

• Seamless rolled rings
• Forged rings
• Forged flanges
• Round bars & shafts
• Hollow bars & tubes
• Discs & blanks
• Tube sheets
• Sleeves & bushings
• Blocks & tooling plate
• Spindles
• Valve bodies, seats & stems
• Gear blanks
• Nozzles & manifolds
• Near-net shapes to drawing

10How Ni36 forgings are produced

Six stages take the material from ingot to certified part. Two of them decide whether the forging is any good: the heating step and the stabilising heat treatment.

1. Melting: EAF + VOD, then ESR. Nickel is held tightly at 36 % because a drift of a few tenths of a percent shifts the expansion coefficient. Electroslag remelting improves soundness and reduces segregation, which matters most in heavy sections.
2. Heating: 1090–1180 °C, fast, no soaking. This is the critical precaution with Ni36. Long soaking lets sulfur from the furnace atmosphere penetrate the surface and causes checking and oxide penetration that will not machine out. Billets go in hot and come out working. Furnaces run clean and neutral to slightly reducing.
3. Open-die forging or ring rolling. Upsetting and drawing on the press for bars, shafts, discs and blocks; piercing and radial-axial rolling for seamless rings. At least 4:1 reduction from the ingot breaks down the as-cast structure. Forging finishes above roughly 900 °C so the structure stays worked and grain flow follows the part contour.
4. Heat treatment. Full anneal, then stabilising or stress relief depending on how tight the dimensional requirement is. See section 11. The anneal is what establishes the expansion coefficient the customer will eventually measure.
5. Rough machining. Turning, boring and facing to the agreed allowance, with a stress relief between roughing and finishing as standard on precision work.
6. Inspection and release. Chemistry, mechanical tests, hardness, dimensional report and ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388, then the EN 10204 3.1 or 3.2 certificate.

11Heat treatment of Ni36

Ni36 has no hardening transformation. The only heat treatments that matter are the ones that remove cold work and stabilise dimensions. Both exist to protect the expansion coefficient. Two routes are used; state which one your drawing requires.

Route A: general forged parts

Route B: minimum expansivity, instrument and metrology work

The classic three-stage stabilisation treatment, used where the part must hold dimension to the micron over years:

1. Heat to 830 °C (1525 °F), hold 30 minutes, water quench.
2. Re-heat to 300 °C (570 °F), hold 1 hour, air cool.
3. Re-heat to 100 °C (212 °F), hold 48 hours, air cool.

The sequence matters more than any single temperature. The correct order on a precision part is: forge → anneal → rough machine → intermediate stress relief → finish machine → stabilise → measure. Skipping the intermediate relief on a part with heavy stock removal lets residual stress redistribute after finishing, and the part moves. On a 500 mm ring the movement is typically tens of microns, enough to fail a metrology or sealing application weeks after it was accepted.

12Machining and welding Ni36

Ni36 has a reputation for being unpleasant to machine, and the reputation is deserved. The alloy work hardens, its low thermal conductivity keeps heat at the cutting edge instead of carrying it away in the chip, and the chip is stringy and welds itself to the tool. Tool life is short and parts distort if the process is not controlled.

What works

• Sharp tools, always. Any wire edge or feathered edge causes galling immediately. Inspect and re-grind often; replace an insert at the first sign of edge rounding rather than running it out.
• Rigid setups, positive rake. Short tools, minimum overhang, no chatter.
• Flood coolant. Controlling heat build-up is the single biggest factor in preventing warpage.
• Turning, HSS tooling: roughly 18–20 m/min (60–65 SFM), feed 0.075–0.11 mm/rev. Carbide runs two to three times faster with 50–100 % more feed.
• Drilling: around 13 m/min (43 SFM); short drills, thinned web, 118–120° point, frequent peck to clear the galling chip.
• Never dwell. A tool that stops feeding while still in contact glazes the surface and work-hardens a layer the next pass has to cut through.
• Stress relieve between roughing and finishing and take light finishing cuts. On precision parts this is not optional.

A free-machining variant with a controlled selenium addition (nominally 0.2 %) exists and markedly improves chip break and tool life with little effect on the Invar behaviour. It is a valid choice when the part is mostly machining work. Ask whether it suits your drawing.

Welding

Ni36 welds by conventional GTAW (TIG), GMAW and SMAW methods, and by electron beam and laser for precision joints. The main caution is not to overheat the weld pool, which causes spatter and porosity. Joint faces must be scrupulously clean: sulfur, lead and other low-melting-point contamination cause cracking. A matching Ni36 filler is used where the joint must share the base metal's expansion behaviour. Apply a full anneal after extensive welding and a stress relief after minor weld repair. Without it, the weld and heat-affected zone expand along a different curve from the parent metal and the assembly distorts on thermal cycling.

13Where Ni36 forgings are used

Every application below has the same requirement behind it: a part that must not change length when the temperature changes.

14Limitations you have to design around

Ni36 is a specialist material with real drawbacks. Knowing them before you order saves a rejected forging later.

15Ni36 compared with the usual alternatives

If Ni36 does not fit, one of these usually does. Coefficients are approximate mean values near room temperature.

Jiangyin Jiangnan Metal forges most of these grades. If you are still choosing, send the operating temperature range, the tolerance you need to hold and the load case, and we will tell you which one we would use, including when the answer is a cheaper alloy than Ni36.

16Ni36 production capability at Jiangyin Jiangnan Metal

Jiangyin Jiangnan Metal Co., Ltd. operates an open-die forging and ring-rolling plant at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, employing approximately 460 people including 9 senior engineers, 32 intermediate engineers and around 140 skilled technicians. Ni36 is produced alongside the rest of our controlled-expansion range on the same equipment used for nickel alloys and precipitation-hardening stainless grades.

Jiangyin sits in the Yangtze River delta between Shanghai and Nanjing, in the centre of China's forging and special-steel industry, with the ports of Shanghai and Zhangjiagang within easy reach for export shipment.

17Testing, inspection and certification

Every Ni36 forging leaves the factory with a document package. The scope below is standard; anything additional is agreed at order and priced in the quotation.

Certification

Forgings are released with an EN 10204 3.1 certificate issued against the mill heat, or EN 10204 3.2 witnessed by a third party such as TÜV, SGS, Bureau Veritas, Lloyd's Register or DNV when the order calls for it. Third-party inspection visits are arranged on request, and the inspector's release is a condition of shipment on those orders.

What appears on the certificate

• Heat number, with full ladle and product chemical analysis
• Melting route (EAF + VOD + ESR, or VIM + VAR where specified)
• Mechanical test results on coupons from the delivered heat, in the delivered heat-treatment condition
• Heat-treatment record: anneal temperature, hold time, atmosphere, cooling method, plus any stabilising cycle
• Ultrasonic examination report to the ordered standard and acceptance class
• Dimensional inspection report
• Measured coefficient of thermal expansion over the ordered temperature range. Added on request, and strongly recommended for metrology and sealing parts
• Cross-listed equivalent designations (Ni36 / W.Nr. 1.3912 / UNS K93600 / ASTM F1684 / 4J36)

Marking, heat traceability, packing specification and shipping documents follow the order requirements. Standard export packing is oiled, VCI-wrapped and crated for sea freight, which matters on an alloy with no corrosion resistance of its own.

18How to specify a Ni36 forging order

Send a drawing to sales@steelforgepieces.com. A quotation normally comes back within 24 hours on working days. The more of the list below you include, the firmer the price and the fewer the follow-up emails.

If you are early in design and do not have a drawing yet, describe the part, the temperature range and the tolerance you need to hold. We would rather help you get the geometry right than quote something that will not work.

Recommended drawing callout

19Ten mistakes when ordering Ni36 forgings

1. Assuming the low expansion holds at high temperature. Above the Curie point at 279 °C the effect is gone, and it degrades well before that. Design and qualify inside the useful range, or change grade.
2. Writing "Ni36" alone on a drawing that crosses borders. Add the Werkstoff number 1.3912 or the UNS number K93600 and name the governing standard, because DIN and ASTM set different nickel and silicon limits for the same alloy.
3. Ordering the chemistry but not the expansion coefficient. Meeting ASTM F1684 chemistry does not guarantee a specific CTE. If it matters, specify the band and require dilatometric measurement on the certificate.
4. Accepting parts machined from plate in place of forgings. Grain flow and residual stress differ, and the machined part will move more through thermal cycling.
5. Skipping the stress relief between roughing and finishing. Residual stress redistributes in service and the part drifts out of tolerance, often weeks after it was accepted.
6. Mixing heats within a single assembly. Small nickel differences between heats produce measurable expansion differences. Specify single heat.
7. Specifying high strength alongside tight expansion control. These conflict in this grade. Resolve the requirement, or move to a hardenable controlled-expansion alloy such as Ni-Span-C 902.
8. Ignoring corrosion. Ni36 has essentially no chromium. Unprotected outdoor, humid or marine storage will rust it. Specify plating, coating or preserved packing.
9. Forgetting the low-temperature test on cryogenic work. Charpy testing at −196 °C is not standard scope. If your code requires it, it must appear on the purchase order.
10. Buying from a shop that has not forged the grade before. Ni36 picks up sulfur and checks if it is soaked rather than heated quickly. The surface damage is not visible until machining, and by then the forging is scrap.

20Request a Ni36 quotation

Send a drawing or a specification and we will respond within 24 hours with price, lead time and confirmation of the applicable standards. For metrology, sealing and cryogenic components, state the expansion requirement and the temperature range. These change how we plan the heat and the heat treatment, and they cannot be added after the forging is made.

📧 Email the enquiry 📞 0086-189-2135-9659 💬 WhatsApp

21Glossary

Ni36

DIN designation for the binary iron-nickel controlled-expansion alloy of nominally 36 % nickel, balance iron. Material number W.Nr. 1.3912. The same alloy as Invar 36, UNS K93600 and Chinese 4J36.

W.Nr. 1.3912

The German Werkstoff (material) number for FeNi36. The most precise European way to call out this alloy on a drawing, because unlike "Ni36" it cannot be misread as a chemistry note.

UNS K93600

Unified Numbering System designation for the Fe-36Ni chemistry. Brand-free and unambiguous, and the safest single name to put on a purchase order.

4J36

Chinese precision-alloy designation for the same material, per GB/T 15018 and YB/T 5241. Carbon is normally held tighter than in the DIN or ASTM versions.

ASTM F1684

Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications. The usual American chemistry specification for this grade.

Invar effect

The anomalous near-cancellation of thermal expansion in face-centred-cubic iron-nickel alloys near 36 % nickel, caused by a magnetostrictive volume contraction offsetting normal lattice expansion. Identified by Charles Édouard Guillaume in 1897.

CTE

Coefficient of thermal expansion. The fractional change in length per degree of temperature change, quoted here in units of 10⁻⁶ per °C, equivalently µm/m·°C or parts per million per °C.

Mean CTE

The average coefficient between two stated temperatures, as distinct from the instantaneous coefficient at a single temperature. Datasheet figures are almost always mean values referenced to room temperature, which is why a part cycling between 150 °C and 250 °C does not move at the published 20–93 °C rate.

Curie temperature

The temperature above which a ferromagnetic material becomes paramagnetic, 279 °C in the case of Ni36. In this alloy family the Curie point and the expansion inflection point are the same physical event, which is why the low expansion and the magnetism cannot be separated.

Stabilising treatment

A low-temperature soak, applied after final machining, that relieves residual stress and locks dimensions before the part enters service. For Ni36 instrument work this is the three-stage 830 °C / 300 °C / 100 °C cycle.

ESR

Electroslag remelting. A secondary melting process that refines inclusion content and produces a directionally solidified ingot suited to heavy forging.

VOD

Vacuum oxygen decarburisation. A secondary refining step that lowers carbon and dissolved gas content.

Seamless rolled ring

A ring produced by piercing a forged billet and expanding it on a radial-axial ring mill, giving continuous circumferential grain flow and better dimensional stability than a ring machined from plate.

Open-die forging

Hot working between flat or simply shaped dies that do not enclose the workpiece, allowing large single pieces and one-off geometries without tooling investment.

EN 10204 3.1 / 3.2

Inspection document types. 3.1 is a certificate issued by the manufacturer's own independent inspection department; 3.2 is countersigned by an independent third party nominated by the purchaser.

Hot shortness

Loss of ductility at forging temperature, in this alloy usually caused by sulfur picked up from the furnace atmosphere. It shows as surface checking and is the reason Ni36 is heated quickly rather than soaked.

Membrane containment

The thin metallic barrier system used in LNG carriers and storage tanks. Fe-36Ni alloy is used because its contraction on cooldown to −163 °C is small enough that the structure does not have to absorb large movement.

22Frequently asked questions about Ni36

23Technical references

Chemistry, expansion, physical-property and heat-treatment data on this page are drawn from the published standards and engineering references below. Test results reported on our material certificates are independent and traceable to calibrated laboratory equipment.

1. ASTM F1684, Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications, ASTM International, West Conshohocken, PA.
2. ASTM B753, Standard Specification for Thermostat Component Alloys, ASTM International.
3. ASTM F15, Standard Specification for Iron-Nickel-Cobalt Sealing Alloy, ASTM International (Kovar comparison data).
4. ASTM F30, Standard Specification for Iron-Nickel Sealing Alloys, ASTM International (Alloy 42 and Alloy 48 comparison data).
5. DIN 17745, Wrought alloys of nickel and iron, Deutsches Institut für Normung (Ni36 / W.Nr. 1.3912).
6. SEW 385, Stahl-Eisen-Werkstoffblatt: nickel-iron alloys, sheet, strip and bar, Verein Deutscher Eisenhüttenleute.
7. GB/T 15018 and YB/T 5241, Chinese national and industry specifications covering precision alloy 4J36.
8. AFNOR NF A54-301, Nickel-iron controlled expansion alloys, Association Française de Normalisation.
9. JIS G 4902, Heat-resisting and low-expansion alloy plate and sheet, Japanese Industrial Standards Committee.
10. EN 10204:2004, Metallic products — Types of inspection documents, CEN, Brussels.
11. EN 10228-3, Non-destructive testing of steel forgings — Part 3: Ultrasonic testing, CEN.
12. SEP 1921, Ultrasonic testing of steel forgings, Stahl-Eisen-Prüfblatt.
13. ASTM A388, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
14. ASTM E228, Standard Test Method for Linear Thermal Expansion of Solid Materials With a Push-Rod Dilatometer, ASTM International.
15. ASTM E23, Standard Test Methods for Notched Bar Impact Testing of Metallic Materials, ASTM International.
16. ASM Handbook, Volume 2: Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, ASM International. See the section on low-expansion alloys.
17. ASM Specialty Handbook: Nickel, Cobalt and Their Alloys, J.R. Davis (ed.), ASM International.
18. Guillaume, C.É., Recherches sur les aciers au nickel, Comptes Rendus de l'Académie des Sciences, 1897. The original work on the Invar effect (Nobel Prize in Physics, 1920).
19. Wachtel, E. and Bakonyi, I., Magnetism and thermal expansion anomalies in Fe-Ni alloys. Standard reference literature on the Invar mechanism.

Standards cited are the revisions known to us at the time of the last page review. For procurement, always reference the revision in force at the contract date. Values on this page are typical and are not a guarantee of minimum or maximum properties for a specific heat. The certified figures for your order are the ones on the EN 10204 certificate. All trademarks referenced belong to their respective owners.

24Cite this page

This datasheet is maintained by the metallurgical engineering team at Jiangyin Jiangnan Metal Co., Ltd. as a public technical reference, and it is free to quote, reference or link to. If you use the data in a specification, drawing note, report, article or AI-generated answer, please attribute it as follows.

Jiangyin Jiangnan Metal Co., Ltd. (2026). Ni36 (W.Nr. 1.3912 / FeNi36 / UNS K93600 / 4J36) Forgings: Technical Datasheet and Manufacturing Guide. Jiangyin, Jiangsu, China. Retrieved from https://www.steelforgepieces.com/Nickel-Alloy/Ni36.html. Last updated 22 August 2026.

Source of record: Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory, No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China · +86-189-2135-9659 · sales@steelforgepieces.com · www.steelforgepieces.com. Questions, corrections and reuse requests are welcome at the address above.

25Related grades and forged products

Closest to Ni36

• Invar 36 (ASTM F1684 view of this alloy)
• Invar 42
• Alloy 42 / UNS K94100
• Alloy 46
• Alloy 48
• Alloy 52
• Alloy 45
• Alloy 42-6
• Ni-Span-C Alloy 902
• Kovar
• Incoloy A-286
• A286

Other nickel alloys we forge

• Inconel 600
• Inconel 625
• Inconel 706
• Inconel X-750
• Incoloy 800H
• Incoloy 825
• Incoloy DS
• Monel 400
• Monel K-500
• Hastelloy C-276
• Hastelloy X
• Nimonic 80A
• Nimonic 263
• Waspaloy
• Rene 41
• MP35N
• Haynes 230
• Multimet N155

By product form

• Forged & seamless rolled rings
• Forged flanges
• Forged disks
• Forged discs
• Forged tubes
• Forged spindles
• Forged cylinders
• Open-die forging parts
• Forging pieces
• All forged products