ALLOY 36 / Invar 36 / UNS K93600 Forging Parts. Low-Expansion Iron-Nickel Forgings for Cryogenic, LNG and Precision Service
ALLOY 36 (UNS K93600, W.-Nr. 1.3912 / FeNi36, widely known by the trademark Invar®) is a binary iron-nickel alloy of nominally 36 % nickel and 64 % iron whose coefficient of thermal expansion is roughly one-tenth that of carbon steel at room temperature. It is the reference material for LNG containment, aerospace composite tooling and metrology structures, it stays ductile and tough down to −196 °C, and it loses its low-expansion behaviour above its Curie temperature of 279 °C. Because ALLOY 36 is a solid-solution alloy it cannot be age hardened, and because it contains essentially no chromium it is not corrosion resistant.
Jiangyin Jiangnan Metal Co., Ltd. is an independent open-die forging factory in Jiangyin, Jiangsu, China that manufactures UNS K93600 forgings to ASTM F1684 and customer specifications: seamless rolled rings to 2,500 mm OD, forged discs to 1,800 mm diameter, shafts to 8 m, bar from 25–500 mm Ø, and single-piece weights to 8,000 kg. Material is melted by EAF + VOD + ESR, supplied annealed and stabilised with EN 10204 3.1 certification as standard, 3.2 third-party witnessed on request, and with a dilatometer CTE report per lot where the drawing requires it. Quotations are issued within 24 hours to sales@steelforgepieces.com or 0086-189-2135-9659.
- UNS
- K93600Fe-Ni low expansion
- Werkstoff
- 1.3912FeNi36
- Nickel
- 36% nominal, bal. Fe
- CTE 20–100 °C
- 1.0–1.6×10⁻⁶/°C
- Curie point
- 279°C (534 °F)
- Density
- 8.05g/cm³
- UTS annealed
- ~490MPa (71 ksi) typ.
- Age hardenable
- Nostrength by cold work only
What Is ALLOY 36 / Invar 36 / UNS K93600?
ALLOY 36 is a binary iron-nickel alloy containing nominally 36 % nickel with iron as the balance. Its defining characteristic is the Invar effect: an anomalously low coefficient of thermal expansion at and around room temperature, roughly one-tenth that of carbon steel and about one-twelfth that of AISI 304 stainless.
The effect was discovered by Charles Édouard Guillaume in 1896 and won him the 1920 Nobel Prize in Physics. Its origin is magnetostrictive. As the ferromagnetic Fe-Ni lattice is heated, the spontaneous magnetisation falls and the lattice contracts. This magnetic contraction very nearly cancels ordinary thermal expansion. The cancellation is sharpest near 36 % nickel, which is why the composition window is held tightly and why nickel content is the single most important number on the material certificate.
At the Curie temperature of 279 °C (534 °F) ALLOY 36 becomes paramagnetic, the magnetic contraction disappears, and the expansion coefficient climbs toward that of ordinary steel, reaching roughly 8.9 × 10⁻⁶/°C by 450 °C. Design work should treat about 200 °C as the practical ceiling for dimensionally critical parts. The material is not damaged above that; it simply stops being a low-expansion alloy.
A note on category. This page sits in the nickel alloy section because that is where buyers look for it, but ALLOY 36 is metallurgically an iron-base controlled-expansion alloy, not a nickel-base superalloy like Inconel 625. It offers no high-temperature strength, no oxidation resistance and no corrosion resistance. It is bought for one reason: the part must not move when the temperature changes.
What Forged Products Are Available in ALLOY 36 / UNS K93600?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory, so every ALLOY 36 item below is forged to the customer's drawing or dimensional sheet. There is no standard catalogue, no die cost and no minimum quantity. Single prototype pieces are normal work.
| Forged form | Typical size range | Where it is used |
|---|---|---|
| Seamless rolled rings | 200–2,500 mm OD | LNG containment, telescope and instrument frames, mould rings |
| Forged rings | To 2,500 mm OD | Positioning structures, gimbal and bearing rings |
| Forged flanges | To 2,000 mm OD | Cryogenic piping, transfer lines, vacuum systems |
| Forged discs and disks | To 1,800 mm Ø | Composite tooling faceplates, optical bench blanks |
| Forged shafts and spindles | To 8 m long | Precision drive shafts, metrology spindles |
| Forged round bar | 25–500 mm Ø | Machined instrument parts, standards, struts |
| Sleeves and bushings | To 1,500 mm OD | Interference-fit spacers, thermally stable bearings |
| Hollow bar and forged tube | To 1,200 mm OD | Waveguide bodies, cryogenic transfer sections |
| Tube sheets | To 1,800 mm Ø | Cryogenic heat exchangers |
| Blocks and forged plate | To 8,000 kg | Composite mould bases, large tool plates |
| Valve bodies, stems, seat rings | To drawing | Cryogenic ball, gate, globe and check valves |
| Nozzles and forged fittings | To drawing | LNG and cryogenic pressure equipment |
Maximum single-piece weight is 8,000 kg. Sizes above are the practical envelope of our presses and ring mill; confirm your specific geometry with the sales team.
What Are the Equivalents of ALLOY 36? (UNS K93600, 1.3912, 4J36, NILO 36)
ALLOY 36 appears on drawings under more names than almost any other engineering alloy, because it was commercialised independently in France, the USA, Germany and Japan. The designations below all describe the same nominal 36 % Ni, balance Fe chemistry.
| System | Designation | Notes |
|---|---|---|
| USA · UNS | K93600, K93603 | K93603 is the conventional grade in ASTM F1684; K93050 is the free-machining variant (bar only) |
| USA · ASTM | F1684 | Iron-nickel alloys for low thermal expansion; chemistry and expansion requirements |
| USA · ASTM | B753, A658/A658M | Thermostat component alloys; 36 % Ni plate and sheet |
| USA · Military | MIL-I-23011 Class 7, MIL-S-16598 | Legacy aerospace and naval procurement; still cited on old drawings |
| EU · DIN / EN | 1.3912 · FeNi36 | Werkstoff number and EN name; DIN 17745 product forms |
| France · AFNOR | NF A54-301 | Chemistry only |
| Japan · JIS | NAS 36 · JIS G 4902 | Low-expansion Fe-Ni sheet and plate |
| China · GB/T | 4J36 · GB/T 15009 | Chinese precision alloy designation for the 36 % Ni chemistry |
| Germany · SEW | SEW 385 | Physical property specification for controlled-expansion alloys |
| Trade names | Invar®, Invar 36®, NILO® 36, Pernifer® 36 | Aperam, Carpenter, Special Metals and VDM respectively. See trademark notice above |
ASTM withdrew F1684-06(2021) in 2024 without direct replacement. A great many drawings still call it out, and it remains a perfectly workable chemistry basis for a purchase order, but if your quality system requires a live standard we can supply to ASTM B753, ASTM A658/A658M, GB/T 15009 (4J36) or a customer specification instead. Say which on the enquiry and the material certificate will reference it correctly.
🔍 Multi-standard designation lookup
Type any name: ALLOY 36, Invar, K93600, 1.3912, FeNi36, 4J36, NILO 36, Super Invar or Kovar, and see every equivalent instantly, or find out that you are on the wrong grade page.
What Is the Chemical Composition of ALLOY 36 / UNS K93600?
The composition below is the chemistry Jiangyin Jiangnan Metal supplies against ASTM F1684 / UNS K93600. Note the unusual structure of the specification: only nickel is controlled to a narrow range, everything else is a maximum, and iron is simply the balance. Nickel is the whole ballgame: a deviation of a few tenths of a percent measurably shifts room-temperature CTE.
| Element | Min | Max | Our typical | Metallurgical role |
|---|---|---|---|---|
| Nickel (Ni) | 35.0 | 37.0 | 36.0 | The Invar effect itself. Below ~34 % the Curie point falls below room temperature and compensation is lost; above ~40 % the magnetic ordering shifts and the effect weakens |
| Iron (Fe) | — | — | bal | Balance. The Fe-Fe magnetic exchange bonds are what generate the magnetovolume contraction |
| Carbon (C) | — | 0.15 | ≤0.05 | Residual. Carbides raise CTE locally and act as dimensional-drift nuclei, so we hold it well below the limit |
| Manganese (Mn) | — | 0.60 | 0.35 | Deoxidiser; combines with residual sulfur |
| Silicon (Si) | — | 0.40 | 0.20 | Deoxidiser. Excess silicon raises expansion |
| Chromium (Cr) | — | 0.25 | ≤0.10 | Residual only. Chromium raises CTE sharply, so it is a contaminant here rather than an alloying addition |
| Cobalt (Co) | — | 0.50 | ≤0.20 | Residual. Deliberate 5 % Co additions give Super Invar, a different grade |
| Phosphorus (P) | — | 0.006 | ≤0.004 | Embrittles grain boundaries. Held well below general spec by ESR |
| Sulfur (S) | — | 0.004 | ≤0.003 | Causes hot shortness during forging and ruins weldability |
Electric arc melting, then vacuum oxygen decarburisation to strip carbon and dissolved gases, then electroslag remelting to give a clean, low-segregation ingot. The ESR step is not decoration on this grade: chemical segregation across an ingot means CTE segregation across the finished part. A ring rolled from a segregated ingot can measure 1.2 × 10⁻⁶/°C on one side and 1.9 on the other, and the customer only discovers it when the assembly will not hold alignment. ESR is how we keep nickel uniform through the section.
What Is the Thermal Expansion of ALLOY 36? The Core Property
This is the number ALLOY 36 is bought for, so it deserves the most careful reading on the page. The mean linear coefficient of thermal expansion between 20 °C and 100 °C is 1.0–1.6 × 10⁻⁶/°C. Carbon steel over the same range is about 11.7 and AISI 304 stainless about 17.3.
| Temperature range | ×10⁻⁶/°C | ×10⁻⁶/°F | Engineering comment |
|---|---|---|---|
| −196 to +20 °C | ≈ 1.5 | ≈ 0.8 | Cryogenic and LNG service; the alloy stays tough throughout |
| 20 to 100 °C | 1.0 – 1.6 | 0.6 – 0.9 | Minimum expansion window; the headline figure |
| 20 to 200 °C | 1.3 – 2.1 | 0.7 – 1.2 | Practical upper design limit; covers the 180 °C composite cure cycle |
| 20 to 260 °C | 2.0 – 3.0 | 1.1 – 1.7 | Approaching the Curie point; expansion rising noticeably |
| 20 to 300 °C | ≈ 5 | ≈ 2.8 | Above Curie; the Invar effect is gone |
| 25 to 450 °C | ≈ 8.9 | ≈ 4.9 | Behaves like an ordinary austenitic steel |
Published CTE values are ranges for a reason. Actual expansion depends on the exact nickel content, the degree of residual cold work, and the thermal history of the piece. Two bars that both pass the same chemical specification can differ by 0.3–0.4 × 10⁻⁶/°C. If your design genuinely depends on the number, specify a measured CTE on the drawing with a tolerance and a temperature range, and require a dilatometer report per lot. We issue one on request. A purchase order that says only "Invar 36" buys you the chemistry, not the expansion coefficient.
📏 Thermal expansion & dimensional drift calculator
Enter a length and a temperature swing to get the movement in ALLOY 36 alongside carbon steel, 304 stainless and aluminium, plus a warning if you have crossed the Curie point.
Uses mean linear CTE over the range. ALLOY 36 values above the Curie point of 279 °C are interpolated from published mean coefficients and rise steeply, so treat results above 260 °C as indicative only and confirm with a dilatometer measurement. Comparison values: carbon steel 11.7, AISI 304 17.3, aluminium 6061 23.1 ×10⁻⁶/°C.
🌡️ Curie point & service temperature checker
Tell it your maximum and minimum service temperature and it will tell you whether ALLOY 36 still behaves as a low-expansion alloy, or whether you have quietly designed yourself out of the Invar effect.
Curie temperature taken as 279 °C. Guidance only. For pressure-retaining parts the governing design code sets the allowable temperature, not this tool.
What Are the Mechanical Properties of ALLOY 36 Forgings?
ALLOY 36 has the tensile properties of a mild austenitic steel. Nobody specifies it for strength, but the numbers matter for handling, machining fixtures and pressure-part calculations.
| Condition | UTS MPa | UTS ksi | YS 0.2 % MPa | YS 0.2 % ksi | Elong. % | Hardness |
|---|---|---|---|---|---|---|
| Annealed (as supplied) | 450–520 | 65–75 | 240–280 | 35–40 | 35–45 | 130–150 HB |
| Annealed + stabilised | ≈490 | ≈71 | ≈240 | ≈35 | ≈42 | ≈140 HB |
| Cold drawn / cold worked | up to 830 | up to 120 | up to 690 | up to 100 | ≥10 | to 30 HRC |
| At −196 °C (annealed) | ≈830 | ≈120 | ≈420 | ≈61 | ≈30 | — |
ALLOY 36 is face-centred cubic and has no ductile-to-brittle transition. It gains strength on cooling while retaining roughly 30 % elongation at −196 °C, and Charpy impact energy stays high throughout. That combination of near-zero contraction and full toughness at LNG temperature is why membrane containment systems for LNG carriers are built from it and not from a cheaper stainless.
It is a single-phase solid solution with no precipitation-hardening additions. There is no ageing treatment, no solution-and-age cycle, no "H1150 condition". If a drawing calls for aged or precipitation-hardened Invar 36, the drawing is wrong. Query it before ordering. Strength above the annealed level can come only from cold work, and cold work is exactly what destroys long-term dimensional stability. If you need both strength and low expansion, the honest answer is a design change, not a heat treatment.
What Are the Physical Properties of ALLOY 36?
| Property | Metric | Imperial | Note |
|---|---|---|---|
| Density | 8.05 g/cm³ | 0.291 lb/in³ | Used by our weight calculator below |
| Melting range | 1427 °C | 2600 °F | Approximate liquidus |
| Curie temperature | 279 °C | 534 °F | The design-critical number |
| Modulus of elasticity | 141–148 GPa | 20.5–21.5 × 10⁶ psi | Rises slightly on cooling |
| Thermal conductivity, 20 °C | 10.15 W/m·K | 70 BTU·in/ft²·h·°F | Low; expect slow, uneven heating in a furnace |
| Specific heat | 515 J/kg·K | 0.123 BTU/lb·°F | — |
| Electrical resistivity | 0.82 µΩ·m | 82 µΩ·cm | — |
| Magnetic behaviour | Ferromagnetic below 279 °C, paramagnetic above | MT inspection is valid on this grade | |
| Crystal structure | Face-centred cubic (austenitic) | No DBTT; coarse grain attenuates ultrasound | |
How Corrosion-Resistant Is ALLOY 36? (Short Answer: It Is Not)
This is the single most common misunderstanding about the grade, and it costs customers money every year. Because ALLOY 36 sits in the nickel-alloy aisle next to Inconel and Hastelloy, buyers assume it shares their corrosion resistance. It does not. ALLOY 36 contains at most 0.25 % chromium and rusts in humid air much like plain carbon steel.
| Environment | Behaviour | Required protection |
|---|---|---|
| Dry indoor / conditioned lab | Stable | Light oil film or nothing; wipe with solvent before assembly |
| Vacuum / inert gas | Stable | None. Degrease and bake out |
| Cryogenic (LNG, LN₂) | Stable | None while cold; protect against condensation on warm-up |
| Humid indoor / unheated store | Surface rust | Phosphate + oil, or VCI packaging |
| Outdoor, sheltered | Rusts | Paint system, electroless nickel or chrome plate |
| Marine atmosphere / splash | Rusts quickly | Full coating system; consider a clad or plated surface |
| Immersed seawater | Unsuitable | Use Alloy 400 or a duplex stainless instead |
| Acids and chemical process | Unsuitable | Use Hastelloy C-276 or Incoloy 825 |
A nickel or chrome plate has a CTE five to ten times higher than the substrate. On a heavy forging this is irrelevant. On a thin plate, a long strut or a large flat tooling face it is not: the coating puts the part into bending as temperature changes, and precision is lost. For dimensionally critical parts specify protection that is either very thin, applied to both faces symmetrically, or a non-metallic option. Tell us the service environment on the enquiry and we will advise before machining, not after.
🛡️ Corrosion protection selector for ALLOY 36
ALLOY 36 has no built-in corrosion resistance, so protection has to be specified deliberately. Describe the service and we will suggest a route that will not wreck your dimensional tolerance.
General engineering guidance. Coating selection for pressure equipment, food contact or aerospace must be confirmed against the governing specification and the coating supplier's data.
ALLOY 36 vs Super Invar, Alloy 42, Kovar, 304L and Carbon Steel
Controlled-expansion alloys are chosen by matching an expansion coefficient to a requirement, not by looking for the lowest number. Picking Super Invar because it expands less than ALLOY 36 is a common and expensive mistake, because its useful window is much narrower.
| Alloy | UNS | Nominal composition | CTE 20–100 °C ×10⁻⁶/°C | Curie | Choose it when |
|---|---|---|---|---|---|
| ALLOY 36 / Invar 36 | K93600 | 36Ni, bal. Fe | 1.0–1.6 | 279 °C | The default. Widest useful range, best cryogenic toughness, LNG, composite tooling, metrology |
| Super Invar 32-5 | K93500 | 32Ni, 5Co, bal. Fe | 0.3–0.6 | ≈230 °C | Absolute minimum expansion, but only in a narrow band near room temperature. Poor below −50 °C |
| Free-cut Invar | K93050 | 36Ni plus S, bal. Fe | 1.0–2.0 | 279 °C | High-volume machined parts. Bar only. Never forge or weld it |
| Alloy 42 / Invar 42 | K94100 | 42Ni, bal. Fe | 4.5–5.5 | ≈355 °C | Sealing to soft glass and ceramics, semiconductor lead frames |
| Alloy 46 / Alloy 48 | K94600 / K94800 | 46Ni / 48Ni, bal. Fe | 7.5–9.5 | ≈400–460 °C | Matching soda-lime and lead glass in lamps and electronics |
| Kovar / ASTM F15 | K94610 | 29Ni, 17Co, bal. Fe | 4.9–5.2 | ≈435 °C | Hermetic sealing to borosilicate hard glass and alumina |
| AISI 304L (reference) | S30403 | 18Cr, 8Ni | ≈17.3 | — | When corrosion resistance matters more than movement |
| Carbon steel (reference) | — | Fe, C | ≈11.7 | — | Baseline for comparison |
Start with ALLOY 36
If the requirement is simply "it must not move", ALLOY 36 is the answer in the great majority of cases and it is the easiest of the family to obtain as a forging.
Move to Super Invar
Only when the service window is narrow and close to ambient, and never for cryogenic work, because Super Invar's expansion rises again below about −50 °C.
Alloy 42 or Kovar
These are matching alloys, not minimising alloys. You choose them to equal the expansion of a specific glass or ceramic, not to reduce expansion.
🎯 Low-expansion alloy selector
Answer four questions about your application and get a ranked recommendation across the whole controlled-expansion family, including the cases where ALLOY 36 is the wrong choice.
A screening tool, not a substitute for design review. Where a part is safety-critical or code-governed, confirm the selection with your own materials engineer.
ALLOY 36 Failure Modes and How to Design Them Out
ALLOY 36 rarely fails by breaking. It fails by moving: slowly, after delivery, in ways that only show up when an assembly no longer holds alignment. These are the mechanisms we see behind returned parts.
Long-term dimensional creep
An unstabilised part keeps shrinking for months as residual stress from machining and cold work relaxes. Typical drift is 20–100 ppm, enough to ruin an optical bench. Fix: full stabilising cycle after rough machining, and again after finish machining on critical parts.
CTE variation within one part
Segregated or inhomogeneous material expands unevenly, bending the component instead of growing uniformly. Fix: ESR-melted stock, adequate forging reduction, and a dilatometer check on the delivered lot.
Curie point exceeded in service
A part specified for 150 °C sees a 300 °C excursion during a bakeout or a paint cure and expands five times more than the design assumed. Fix: state the true maximum excursion, not the nominal duty, on the enquiry.
Corrosion of an unprotected part
Rust pitting on a precision surface, usually after storage rather than in service. Fix: VCI packaging from the factory and a specified protection system.
Weld zone expansion mismatch
A weld made with stainless or nickel filler expands ten times more than the parent metal, warping the assembly on every thermal cycle. Fix: matching Invar 36 filler, no exceptions.
Hot shortness during forging
Sulfur or lead contamination causes intergranular cracking at forging temperature. Fix: low-sulfur furnace atmosphere and degreasing before every heating operation. This is a supplier-side control, and it is worth asking about.
How Do You Forge, Anneal, Stabilise, Machine and Weld ALLOY 36?
Forging
ALLOY 36 forges in a narrower window than steel. Our practice is to heat to 1150–1200 °C and finish above 900 °C; below that the alloy work-hardens rapidly and cracks. Because thermal conductivity is low, soak times are longer than an equivalent steel section. Rushing the soak gives a cold core and a torn surface. Total reduction of at least 4:1 from the ingot is required to break down the cast structure; on ring-rolled parts we take the reduction in the upset and punch stages so the rolled ring finishes with continuous circumferential grain flow.
- MeltEAF + VOD + ESR. Nickel confirmed by spectrometer on every heat
- Heat1150–1200 °C, extended soak for the low conductivity
- ForgeUpset and draw, ≥4:1 reduction, finish above 900 °C
- Ring rollFor rings: continuous circumferential grain flow
- Anneal830 °C, rapid cool
- Rough machineLeave finishing stock before stabilising
- StabiliseThree-stage cycle for dimensional work
- Finish & NDEFinal machining, UT and PT, dimensional report
Annealing and dimensional stabilisation
Annealing is at approximately 830 °C (1525 °F) with rapid cooling. That alone gives you the mechanical properties in Table 5, but it does not give long-term dimensional stability. For that, the classic three-stage cycle is applied after rough machining:
| Stage | Temperature | Hold | Cool | What it does |
|---|---|---|---|---|
| Stage 1, solution | 830 °C (1525 °F) | 30 min per 25 mm section | Water quench | Dissolves carbides, resets the structure |
| Stage 2, stress relief | 315 °C (600 °F) | 1 hour | Air cool | Removes quench stress without re-precipitating |
| Stage 3, stabilise | 95 °C (200 °F) | 48 hours | Air cool | Exhausts the slow room-temperature drift that would otherwise appear over months in service |
Stage 3 is the one customers most often omit and most often regret. It is cheap, it takes two days, and it is the difference between a part that holds alignment for a decade and one that walks out of tolerance in the first year.
♨️ Stabilising heat-treatment recipe generator
Enter your section thickness and precision class and get the full cycle with calculated soak times, ready to paste onto a drawing or a heat-treatment purchase order.
Soak times calculated at 30 minutes per 25 mm of section for the solution stage, with a 30-minute minimum. Furnace atmosphere must be low in sulfur; parts must be degreased before every heating operation.
Machining
ALLOY 36 machines like a gummy austenitic stainless. It work-hardens fast, builds up on the cutting edge and tears rather than chipping cleanly. The free-machining variant UNS K93050 exists precisely because standard Invar is such hard work, but K93050 is bar only, and it cannot be forged or welded, so it is not an option for the parts on this page.
Every cut leaves residual stress in the surface, and on ALLOY 36 that stress relaxes over months. On precision parts, machine in stages: rough, stabilise, semi-finish, stabilise, finish. Never take a heavy final cut on a part that has to hold microns.
⚙️ ALLOY 36 machinability advisor
Starting parameters for turning, milling, drilling and boring on ALLOY 36. The alloy is roughly 30 % of the machinability of B1112 free-cutting steel, so steel numbers will not work.
Starting values for annealed material, rigid setup and flood coolant. Adjust to your machine, tooling and part rigidity. Always verify on a test cut before committing an expensive forging.
Welding
ALLOY 36 welds readily by GTAW, GMAW and SMAW. The rule that overrides everything else is matching filler: an Invar 36 weld deposit expands like the parent metal, and a stainless or nickel deposit does not. A 308L weld in an Invar structure expands roughly ten times more than the material around it, and every thermal cycle bends the assembly a little further.
🔥 ALLOY 36 welding procedure advisor
Filler selection, heat input guidance and post-weld treatment for Invar 36 joints, including the cases where the honest answer is "do not weld this here".
Guidance only. Production welding requires a qualified WPS/PQR to the applicable code (ASME IX, EN ISO 15614). We supply forgings, not welding procedures.
ALLOY 36 Production Capability at Jiangyin Jiangnan Metal
Jiangyin Jiangnan Metal Co., Ltd. has forged open-die parts since 2008 from a plant at No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, and exports to more than 40 countries under an ISO 9001:2015 quality system.
| Parameter | Capability |
|---|---|
| Single-piece weight | Up to 8,000 kg (17,600 lb) |
| Seamless rolled ring OD | 200 – 2,500 mm |
| Forged disc diameter | Up to 1,800 mm |
| Shaft length | Up to 8,000 mm |
| Round bar diameter | 25 – 500 mm |
| Melting practice | EAF + VOD + ESR |
| Delivery condition | As-forged, annealed, annealed + stabilised, rough machined or finish machined |
| Minimum order | Single prototype pieces accepted; no die cost on open-die work |
| Certification | EN 10204 3.1 standard; 3.2 third-party witnessed on request |
| Quotation turnaround | Within 24 hours of a complete enquiry |
⚖️ ALLOY 36 forging weight calculator
Pick a shape and dimensions for an instant net weight at the UNS K93600 density of 8.05 g/cm³, plus an estimated rough forging weight for your RFQ.
Calculated at 8.05 g/cm³. The result is the finished net weight; the rough forging weight adds the selected machining allowance. Maximum single-piece capability is 8,000 kg.
Which Standards, Testing and Certification Apply to ALLOY 36 Forgings?
For UNS K93600 the chemistry basis is normally ASTM F1684, with ASTM B753, ASTM A658/A658M or GB/T 15009 (4J36) as live alternatives. What catches most buyers out is not the material specification but the non-destructive examination callouts, which are routinely copied across from steel-forging drawings and do not apply.
EN 10228-3 and SEP 1921 are ultrasonic standards written for ferritic and martensitic steel forgings. ALLOY 36 is face-centred cubic and coarse grained: it attenuates and scatters ultrasound very differently, and the acceptance classes in those standards were never calibrated for it. The appropriate practice for wrought non-ferritic products is ASTM E2375, with acceptance agreed between purchaser and supplier; where a European framework is required, the austenitic approach of EN 10228-4 is the closer analogue. Surface examination is liquid penetrant to ASTM E165 / E1417.
One genuine difference from the nickel-base alloys next to it in our catalogue: ALLOY 36 is ferromagnetic below 279 °C, so magnetic particle testing to ASTM E1444 is valid on this grade, unlike Alloy 400, Inconel or Hastelloy, where MT is meaningless. If your quality plan already calls for MT, it will work here.
| Test | Standard | Applied |
|---|---|---|
| Chemical analysis | Spectrometer + combustion C/S | Every heat; nickel reported to two decimals |
| Tensile | ASTM E8 / ISO 6892-1 | Every lot |
| Hardness | ASTM E10 / E18 | Every lot |
| Charpy impact | ASTM E23 / ISO 148 | On request; −196 °C testing for cryogenic and LNG orders |
| Thermal expansion (CTE) | ASTM E228 dilatometry | On request, per lot, over the customer's stated temperature range |
| Ultrasonic | ASTM E2375 (or EN 10228-4 approach) | To the acceptance class on the order |
| Liquid penetrant | ASTM E165 / E1417 | On request |
| Magnetic particle | ASTM E1444 | Valid on this grade; on request |
| Grain size | ASTM E112 | On request |
| Dimensional report | To customer drawing | Before despatch |
| Certificate | EN 10204 3.1 | Standard on every order |
| Certificate, witnessed | EN 10204 3.2 | BV, SGS, TÜV, Lloyd's; on request |
Where Is ALLOY 36 Used? Applications by Industry
Membrane containment and transfer
ALLOY 36 barely contracts on cooling to −162 °C and keeps full toughness there, so membrane containment systems, transfer lines, cryogenic flanges and heat exchanger tube sheets stay dimensionally predictable through every loading cycle.
Composite tooling
An autoclave mould for carbon fibre must not grow relative to the part through a 180 °C cure. ALLOY 36 is the industry answer, and large tool bases, faceplates and mould rings start as forged plate, discs or rolled rings.
Precision instruments
Optical and laser bench frames, ring laser gyroscope bodies, interferometer and telescope structures, length standards and gauge blocks. Anywhere a micron of drift is a failure.
Positioning and RF hardware
Stages, mounts and frames that must hold position across temperature, plus microwave cavity resonators and waveguide bodies that must hold tuning.
Cryogenic valve components
Forged bodies, bonnets, stems and seat rings for cryogenic ball, gate, globe and check valves, plus nozzles and flanges for cryogenic pressure equipment.
Thermostatic devices
As the low-expansion leg of a bimetal strip, ALLOY 36 converts temperature into predictable movement in thermostat elements, balance wheels and pendulum rods.
How to Specify and Order an ALLOY 36 Forging
A complete enquiry gets a complete quotation in 24 hours. An incomplete one gets a round of questions first, which costs you a day. These are the eight things we need:
- Grade and specification: "ALLOY 36 / UNS K93600 to ASTM F1684" or the live standard you prefer
- Geometry: a drawing, or OD × ID × height for rings, or Ø × length for bars and shafts
- Quantity and target delivery date
- Delivery condition: as-forged, annealed, annealed + stabilised, rough or finish machined
- CTE requirement: the value, the tolerance and the temperature range, if it is critical. This is the item most often left off
- Service environment and temperature, including any excursions above the nominal duty
- NDE requirement and acceptance class, remembering the note above about steel standards
- Certificate type: EN 10204 3.1 or 3.2, and any third party you need
Ten Mistakes Engineers Make When Ordering ALLOY 36
- Ordering "Invar 36" and expecting a guaranteed CTE. The grade name buys chemistry. Expansion has to be specified and measured separately.
- Assuming it resists corrosion because it lives in the nickel alloy catalogue. It has no chromium. It rusts.
- Skipping the 95 °C / 48 h stabilising stage to save two days, then finding the part has drifted out of tolerance six months later.
- Copying EN 10228-3 or ASTM A388 onto the order from a steel drawing. Those are ferritic-steel ultrasonic standards.
- Specifying an aged or precipitation-hardened condition. There is no such thing for this alloy.
- Choosing Super Invar for a cryogenic job because its room-temperature CTE looks better. Its expansion rises again below about −50 °C.
- Welding with 308L or Inconel filler because that is what was on the shelf, then wondering why the frame bows on every thermal cycle.
- Nickel-plating a thin precision part on one face only, turning it into a bimetal strip.
- Quoting the nominal duty temperature and forgetting the bakeout, the paint cure or the steam clean that takes the part past 279 °C.
- Ordering free-cut Invar (K93050) for a forged or welded part. The sulfur that makes it machinable makes it impossible to forge or weld.
Drawing Callout Template for ALLOY 36
Copy this onto the drawing, delete what does not apply, and the material certificate will come back referencing exactly what you asked for.
| Line | Text |
|---|---|
| Material | ALLOY 36 (Invar 36), UNS K93600, W.-Nr. 1.3912 / FeNi36, per ASTM F1684 chemistry |
| Melt practice | EAF + VOD + ESR. Ni 35.5–36.5 %. C ≤ 0.05 %, S ≤ 0.003 %, P ≤ 0.004 % |
| Manufacture | Open-die forged, minimum 4:1 reduction; rolled rings with continuous circumferential grain flow |
| Condition | Annealed 830 °C + stabilised (315 °C / 1 h + 95 °C / 48 h) after rough machining |
| Expansion | Mean CTE 20–100 °C shall be ≤ 1.6 × 10⁻⁶/°C, verified per lot by dilatometry to ASTM E228; report required |
| Mechanical | Tensile per ASTM E8; hardness per ASTM E18. Charpy at −196 °C where cryogenic service applies |
| NDE | Ultrasonic per ASTM E2375, acceptance class per PO. Penetrant per ASTM E165. MT per ASTM E1444 permitted (material is ferromagnetic) |
| Protection | Preserve with VCI packaging. Do not apply single-sided plating to sections under 6 mm |
| Certification | EN 10204 3.1 (or 3.2 witnessed by ____) |
| Marking | Heat number, grade, PO number, piece number |
Glossary of ALLOY 36 Terms
- Invar effect
- The anomalously low thermal expansion of Fe-Ni alloys near 36 % nickel, caused by a magnetic contraction that cancels ordinary lattice expansion.
- Curie temperature
- 279 °C for ALLOY 36. Above it the alloy is paramagnetic and the Invar effect disappears.
- CTE
- Coefficient of thermal expansion. Always quote it with a temperature range, because the number is meaningless without one.
- Dimensional stabilisation
- The 830 °C / 315 °C / 95 °C three-stage cycle that exhausts long-term dimensional drift.
- ESR
- Electroslag remelting. Produces a clean, low-segregation ingot. Essential here, because segregation means CTE variation.
- Magnetostriction
- Change of dimension with magnetic state. The physical mechanism behind the Invar effect.
- Super Invar
- 32Ni-5Co-Fe, UNS K93500. Lower CTE than ALLOY 36 but over a narrower window and poor below −50 °C.
- Free-cut Invar
- UNS K93050. Sulfur-bearing machinable variant, bar only. Cannot be forged or welded.
- 4J36
- The Chinese GB/T 15009 designation for the same 36 % Ni chemistry.
- EN 10204 3.1 / 3.2
- Material certificate issued by the manufacturer's own inspection department (3.1) or witnessed by an independent third party (3.2).
Frequently Asked Questions on ALLOY 36 / Invar 36 / UNS K93600
Is ALLOY 36 the same as Invar 36?
Yes. ALLOY 36, Alloy 36, Invar 36, FeNi36, NILO 36, Pernifer 36 and Chinese grade 4J36 all describe the same iron-nickel alloy with nominally 36 % nickel, covered by UNS K93600/K93603 and W.-Nr. 1.3912. Invar® is a registered trademark of Aperam Alloys Imphy; ALLOY 36 is the generic designation, and it is what Jiangyin Jiangnan Metal Co., Ltd. supplies.
What is the coefficient of thermal expansion of ALLOY 36?
The mean linear coefficient of thermal expansion of ALLOY 36 is 1.0–1.6 × 10⁻⁶/°C between 20 °C and 100 °C, and 1.3–2.1 × 10⁻⁶/°C between 20 °C and 200 °C. That is roughly one-tenth the expansion of carbon steel and one-twelfth that of AISI 304 stainless. Above the Curie temperature of 279 °C the value climbs to about 5 × 10⁻⁶/°C and reaches roughly 8.9 × 10⁻⁶/°C by 450 °C.
What is the maximum service temperature of ALLOY 36?
About 200 °C for dimensionally critical work. ALLOY 36 loses its low-expansion behaviour at the Curie temperature of 279 °C (534 °F), where the alloy becomes paramagnetic. The material is not damaged above that temperature; it simply stops being a low-expansion alloy and expands like an ordinary austenitic steel.
Is ALLOY 36 magnetic?
Yes. ALLOY 36 is ferromagnetic below its Curie temperature of 279 °C and paramagnetic above it. The magnetism and the Invar effect are the same phenomenon, because the low expansion exists only while the alloy is magnetically ordered. A practical consequence is that magnetic particle inspection to ASTM E1444 is valid on ALLOY 36, unlike on nickel-base alloys such as Alloy 400 or Inconel 625.
Is ALLOY 36 corrosion resistant?
No. ALLOY 36 contains at most 0.25 % chromium and corrodes much like carbon steel. It is specified for dimensional stability and cryogenic toughness, not for corrosion resistance. Parts exposed to humidity, weather or marine atmosphere need plating, painting, phosphating or another applied coating, and precision parts need that protection chosen carefully so the coating does not distort the component.
Can ALLOY 36 be age hardened or heat treated to higher strength?
No. ALLOY 36 is a single-phase solid-solution alloy with no precipitation-hardening additions, so there is no ageing or solution-and-age treatment for it. Strength above the annealed level of roughly 490 MPa can come only from cold work, and cold work degrades long-term dimensional stability. If a drawing specifies an aged condition for Invar 36, the drawing is in error.
Can ALLOY 36 be welded?
Yes. ALLOY 36 welds readily by GTAW, GMAW and SMAW, but the filler must be matching Invar 36. A stainless or nickel filler deposits weld metal that expands five to ten times more than the parent material, which warps the assembly on every thermal cycle. Use low heat input and stringer beads to control distortion; preheat is not normally required. Keep the joint free of sulfur, lead and other low-melting contaminants, and stabilise after welding if dimensions are critical.
What is the difference between ALLOY 36 and Super Invar?
Super Invar (32Ni-5Co-Fe, UNS K93500) has a lower coefficient of thermal expansion of about 0.3–0.6 × 10⁻⁶/°C, but only across a narrow band near room temperature, and its Curie point is lower at roughly 230 °C. Its expansion also rises again below about −50 °C, which makes it a poor choice for cryogenic work. ALLOY 36 has a slightly higher CTE of 1.0–1.6 × 10⁻⁶/°C but holds it across a much wider and more useful range and stays tough to −196 °C. Most LNG and composite tooling work therefore uses ALLOY 36.
Why does the CTE of my ALLOY 36 lot differ from the datasheet?
Because the coefficient of thermal expansion of ALLOY 36 is a property of the individual lot, not of the grade. It depends on the exact nickel content, the amount of residual cold work and the thermal history of the piece, and two bars that both meet the chemical specification can differ by 0.3–0.4 × 10⁻⁶/°C. If your design depends on the value, specify it on the drawing with a tolerance and a temperature range and require a dilatometer report to ASTM E228 per lot. Jiangyin Jiangnan Metal Co., Ltd. issues one on request.
What forged shapes of ALLOY 36 can be supplied, and how large?
Jiangyin Jiangnan Metal Co., Ltd. forges ALLOY 36 into seamless rolled rings to 2,500 mm outside diameter, forged discs to 1,800 mm diameter, shafts to 8 m long, round bar from 25 to 500 mm diameter, plus flanges, sleeves, bushings, hollow bar, tube sheets, blocks, valve bodies, stems, seat rings and nozzles. Maximum single-piece weight is 8,000 kg. All shapes are made to the customer's drawing; open-die forging means no die cost and no minimum quantity.
What certificates are supplied with ALLOY 36 forgings?
EN 10204 3.1 mill certificates are standard on every ALLOY 36 order from Jiangyin Jiangnan Metal Co., Ltd. EN 10204 3.2 certificates witnessed by a third party such as BV, SGS, TÜV or Lloyd's are available on request. Testing includes chemical analysis per heat, tensile to ASTM E8, hardness to ASTM E18, Charpy impact at −196 °C for cryogenic orders, ultrasonic examination to ASTM E2375, and dilatometer CTE measurement to ASTM E228 where the drawing requires it.
Who supplies ALLOY 36 forgings, and how do I get a quotation?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forging since 2008 and exporting ALLOY 36 forgings to more than 40 countries under ISO 9001:2015. Send a drawing or the basic dimensions to sales@steelforgepieces.com or call 0086-189-2135-9659. Include the grade, dimensions, quantity, delivery condition, service temperature, any CTE requirement and the certificate type, and a quotation follows within 24 hours.
📋 ALLOY 36 RFQ generator
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Technical References
- ASTM F1684-06(2021), Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications, ASTM International (withdrawn 2024).
- ASTM B753, Standard Specification for Thermostat Component Alloys, ASTM International.
- ASTM A658/A658M, Standard Specification for Pressure Vessel Plates, Alloy Steel, 36 Percent Nickel, ASTM International.
- ASTM E228, Standard Test Method for Linear Thermal Expansion of Solid Materials With a Push-Rod Dilatometer, ASTM International.
- ASTM E2375, Standard Practice for Ultrasonic Testing of Wrought Products, ASTM International.
- GB/T 15009, Precision alloys, designation 4J36, Standardization Administration of China.
- DIN 17745, Wrought alloys of nickel and iron, Deutsches Institut für Normung.
- Guillaume, C. É. (1897), Recherches sur les aciers au nickel. The original description of the Invar effect.
- EN 10204, Metallic products: Types of inspection documents, CEN.
- NACE / ISO and ASME references as applicable to the specific pressure-retaining application.
Standards cited are the revisions known at the time of the last page review. For procurement, always reference the revision in force at contract date. Trademarks and copyrights belong to their respective owners.
Request an ALLOY 36 / UNS K93600 Forging Quotation
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Related Controlled-Expansion and Nickel Alloy Forging Grades
If ALLOY 36 is not the right fit for your application, these grades cover the adjacent requirements:
- Invar 36 and Invar 42: the same family; Invar 42 for soft-glass and ceramic sealing
- Kovar (ASTM F15): hermetic sealing to borosilicate hard glass and alumina
- Alloy 46, Alloy 48, Alloy 52: higher controlled expansion for glass sealing
- Alloy 42-6 and NI-SPAN-C Alloy 902: constant-modulus and specialised expansion alloys
- Alloy 400 (UNS N04400): when the part is in seawater and expansion does not matter
- Inconel 625 and Hastelloy C-276: corrosive service and high temperature
- Incoloy A-286 and A286: cryogenic strength where low expansion is not required
Page last reviewed 12 August 2026 by the Jiangyin Jiangnan Metal Co., Ltd. Metallurgical Engineering Team. Data is provided for engineering guidance; confirm all values against the governing specification revision for your contract.