Controlled-expansion nickel-iron alloy · Open-die forgings
NILO 52 Forgings Alloy 52 · UNS N14052 · W.Nr. 2.4478 · ASTM F30. Seamless rolled rings, discs, shafts, flanges, bars and tube sheets, forged to drawing.
- UNS N14052
- ASTM F30
- W.Nr. 2.4478
- Alloy 52
- Glass Sealing 52
- Invar 52
- Pernifer 50
- AWS 093
- 4J50
Summary
NILO 52 is a controlled-expansion nickel-iron alloy containing a nominal 50.5% nickel with the balance iron, specified to ASTM F30 and designated UNS N14052 (W.Nr. 2.4478). Its coefficient of thermal expansion is low and almost constant from room temperature to about 565 °C (1050 °F), at roughly 9.8 µm/m·°C. That value is matched to soft lead and soda-lime sealing glasses, so glass-to-metal seals stay hermetic and free of cracks.
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges NILO 52 to customer drawings as seamless rolled rings, discs, shafts, flanges, round bars, sleeves, bushings, tube sheets and forged pipe. Material is melted by EAF + VOD + ESR, annealed at 850–1000 °C, ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388, and certified to EN 10204 3.1 or 3.2. Quotations: sales@steelforgepieces.com · +86 189 2135 9659.
- Nominal nickel
- 50.5 %
- Mean CTE 25–450 °C
- 9.8 µm/m·°C
- Constant to
- 565 °C
- Density
- 8.25 g/cm³
- Rolled ring OD
- 2 500 mm max
- Single piece
- 8 000 kg max
01Designations and equivalent grades
NILO 52 appears on drawings and purchase specifications under several different names, because mills, standards bodies and national systems each named it separately. All of them describe the same 50.5% nickel iron-nickel sealing alloy. If your drawing carries any designation in the table below, Jiangyin Jiangnan Metal can forge it.
| System / origin | Designation | Note |
|---|---|---|
| UNS (USA) | N14052 | Primary designation for ordering |
| ASTM | ASTM F30, Class 2 | Iron-nickel sealing alloys for glass and ceramics |
| Werkstoff / DIN | 2.4478 (DIN 17745) | German material number |
| Aerospace | AMS-I-23011, Class 2 | Supersedes MIL-I-23011C |
| AWS | AWS 093 | Welding / filler designation |
| China (GB/YB) | 4J50 | Precision alloy series |
| Trade & common names | Alloy 52 · 52 Alloy · N52 | Generic industry names |
| Producer trade names | NILO® 52 · Pernifer® 50 · Glass Sealing 52 · Invar 52 | Trademarks of their respective owners. See the notice below. |
Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from published alloy specifications. Where a drawing calls a producer trade name, we supply generic UNS N14052 to ASTM F30 unless the drawing requires certified material from a specific mill.
02Chemical composition
The nickel content of NILO 52 is nominal rather than a fixed target. ASTM F30 allows the melter to adjust nickel within the specification so that the finished material meets the required thermal expansion. The property being ordered is the expansion behaviour, and the chemistry is the means of reaching it. Every heat we forge is supplied with its ladle analysis on the mill certificate.
| Element | Symbol | Composition, wt % | Function |
|---|---|---|---|
| Iron | Fe | Balance | Base metal |
| Nickel | Ni | 50.5 nominal | Sets the expansion curve; adjusted by the melter to meet CTE |
| Cobalt | Co | — | Not intentionally added in Alloy 52 (unlike Kovar / ASTM F15) |
| Carbon | C | 0.05 max | Held low to avoid carbide-driven expansion drift |
| Silicon | Si | 0.30 max | Deoxidiser residue |
| Sulfur | S | 0.025 max | Held low for hot workability and seal integrity |
| Chromium | Cr | 0.025 max | Residual; restricted to protect glass wetting |
Source: Jiangyin Jiangnan Metal Co., Ltd., NILO 52 forging specification. Manganese and phosphorus are controlled to the ASTM F30 limits. The certified ladle analysis of each heat, and a product analysis where the order calls for one, are reported on the EN 10204 3.1 or 3.2 certificate.
Melting route. NILO 52 for forging is melted by EAF + VOD + ESR. Vacuum oxygen decarburisation strips carbon and gases. Electroslag remelting refines the ingot structure and removes inclusions. Both steps matter for this grade, because inclusions and gas porosity can become leak paths in a finished glass-to-metal seal.
03Mechanical properties
Values below are typical room-temperature properties for annealed NILO 52. Actual results for your heat are reported on the mill certificate. NILO 52 is selected for its expansion behaviour, and strength is a secondary consideration.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 552 MPa | 80 ksi |
| Yield strength, 0.2 % offset | 276 MPa | 40 ksi |
| Elongation | 35 % | 35 % in 2 in. |
| Hardness, typical | ≈ 150 HB | ≈ 78 HRB |
| Condition as supplied | Annealed | Annealed |
Source: Jiangyin Jiangnan Metal Co., Ltd., NILO 52 forging specification. Published typical ranges for Alloy 52 across producers run 517–552 MPa tensile, 240–276 MPa yield and 30–35 % elongation; hardness is indicative only and is not certified unless the order requires it.
04Physical and thermal properties
The expansion figures below govern grade selection for sealing work. The remaining values are given for design comparison.
| Property | Typical value | Comment |
|---|---|---|
| Density | 8.25–8.30 g/cm³ | 0.30 lb/in³. Use 8.25 for forged weight estimates. |
| Melting range | 1425–1455 °C | 2600–2650 °F |
| Mean CTE, 25–450 °C | 9.8 µm/m·°C | 5.4 µin/in·°F |
| Expansion stable to | ≈ 565 °C | 1050 °F. Practical upper limit for sealing. |
| Thermal conductivity, 20 °C | ≈ 12.7–14 W/m·K | Low; allow for it in seal heating cycles |
| Magnetic behaviour | Ferromagnetic | Fairly high saturation induction and permeability |
| Annealing range | 850–1000 °C | 1560–1830 °F, soak by section, controlled cool |
| Hot forging range | ≈ 1150 → 900 °C | Finish above 900 °C; avoid cold work |
Typical values compiled by Jiangyin Jiangnan Metal Co., Ltd. from published Alloy 52 / UNS N14052 datasheets. Figures are indicative for design comparison; certified values for a specific heat are stated on the EN 10204 certificate. Where a project depends on a precise expansion curve, order dilatometer testing with the forgings.
Cold work. Residual cold work distorts the coefficients of thermal expansion in this alloy family. NILO 52 is therefore hot forged and supplied annealed, and finish machining is planned so that the part is not left with heavy cold deformation before sealing.
05Glass-to-metal seal match
As a glass-to-metal seal cools, the metal and the glass contract at different rates. The difference is carried by the glass, which has very low tensile strength. NILO 52 contracts at close to the same rate as soft lead and soda-lime glass, which leaves the glass in mild compression rather than in tension.
Seal match calculator Tool 01
Set a seal length and a cool-down range, then compare the metal against the glass you are sealing to. The differential contraction is how far the two materials move apart over the length of the seal.
Indicative first-pass screening only. A real seal design also depends on the glass set point, the seal geometry (compression, matched or housekeeper), oxide layer control and the full expansion curves rather than single mean values. Jiangyin Jiangnan Metal supplies the forging; seal qualification remains with the designer.
06Forged product forms and size capability
All sizes below are made to drawing. Open-die forging carries no tooling charge and no die-cost minimum, so single prototype pieces and small batches are normal work.
| Product form | Size range | Typical use in NILO 52 |
|---|---|---|
| Seamless rolled rings | 200–2 500 mm OD | Seal rings, housing rings, spacer rings |
| Forged discs / discs blanks | to Ø 1 800 mm | Tube sheets, header plates, seal plates |
| Forged shafts and spindles | to 8 000 mm length | Instrument spindles, positioning shafts |
| Forged round bars | Ø 25–500 mm | Machining stock for feedthroughs and pins |
| Forged flanges | to 2 500 mm OD | Hermetic housing flanges, lamp bases |
| Sleeves and bushings | to 1 500 mm OD | Eyelet and compression seal bodies |
| Tube sheets | to Ø 1 800 mm | Multi-feedthrough plates |
| Forged pipe and hollows | per drawing | Bored hollows for sealed enclosures |
| Blocks and rectangles | per drawing | Machined housings and frames |
| Maximum single-piece weight | ≈ 8 000 kg | Confirm per geometry at enquiry |
Capability envelope of Jiangyin Jiangnan Metal Co., Ltd. Achievable size for any one part depends on geometry, forging ratio and the ingot size available in this grade. Send the drawing and we will confirm feasibility with the quotation.
Forged weight estimator Tool 02
Estimate the rough forged weight of a NILO 52 part at 8.25 g/cm³, before machining allowance. Useful for budget pricing before a drawing is finished.
07How we forge NILO 52
Two variables control the result when forging NILO 52: finishing temperature and residual cold work. Both alter the thermal expansion curve. The route below is set up to control them.
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Melting: EAF + VOD + ESR
Electric arc melting, vacuum oxygen decarburisation to strip carbon and dissolved gas, then electroslag remelting to refine the ingot and reduce inclusions. Inclusions and gas porosity can become leak paths in a finished seal, so melt cleanliness is specified on the order.
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Open-die forging and ring rolling
Heated to roughly 1150 °C and forged down with a finishing temperature held above 900 °C. The works runs 1, 3, 5 and 9 tonne forging hammers, a 5 000 tonne hydraulic press, and 3 m and 6 m seamless ring rolling mills. Forging ratio is set to break down the cast structure through the full section.
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Annealing, 850–1000 °C
Every forging is annealed, with soak time set by section thickness and a controlled cool. Annealing removes forging strain and restores the expansion behaviour, which is why NILO 52 is ordered and used in the annealed condition rather than cold-finished.
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Rough or finish machining
Turned, bored and faced in house to the drawing. Machining strategy is planned to avoid leaving heavy cold deformation in surfaces that will later be sealed to glass.
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Testing and inspection
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 to the class stated on the order. Chemical analysis, tensile testing, hardness, grain size and dimensional inspection as required. Dilatometer testing of the expansion curve can be added when the application demands it.
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Certification and despatch
EN 10204 3.1 mill test certificate as standard, or EN 10204 3.2 countersigned by a third party such as SGS, BV, TÜV or Lloyd's Register. Heat number traceability is maintained from ingot to packed part.
| Equipment | Capacity |
|---|---|
| Open-die forging hammers | 1 t · 3 t · 5 t · 9 t |
| Hydraulic forging press | 5 000 t |
| Seamless ring rolling mills | 3 m and 6 m |
| Heat treatment | Annealing, normalising, quench and temper furnaces |
| Non-destructive testing | Ultrasonic · magnetic particle · dye penetrant |
| Laboratory | Spectrometer · universal testing machine · impact tester · hardness tester · metallographic microscope |
| Quality system | ISO 9001:2015 |
Jiangyin Jiangnan Metal Co., Ltd. Open-die forging works, Jiangyin, Jiangsu Province, China. Established 2008.
Annealing cycle planner Tool 03
A starting point for the anneal on a NILO 52 forging, based on the ruling section. Confirm against your own procedure or ours before running production.
08NILO 52 compared with the other sealing alloys
The iron-nickel sealing alloys are not interchangeable. Each has a different expansion value, and the grade is selected to match the glass or ceramic on the other side of the seal. Substituting on price or availability rather than expansion is a common cause of seal failure.
| Alloy | Nominal Ni | Mean CTE | Matched to | Choose it when |
|---|---|---|---|---|
| Invar 36 | 36 % | ≈ 1.3 µm/m·°C | Nothing. Near-zero movement. | Dimensional stability is the requirement: instruments, moulds, LNG containment |
| Alloy 42 / Invar 42 | 42 % | ≈ 4.5–5.3 µm/m·°C | Hard borosilicate glass, alumina, silicon | Sealing to hard glass or bonding to silicon in lead frames |
| Kovar / ASTM F15 | 29 % Ni + 17 % Co | ≈ 5.1 µm/m·°C | Hard borosilicate glass, alumina | Hermetic microelectronic packages needing a flat curve to 450 °C |
| Alloy 48 | 48 % | ≈ 8.5 µm/m·°C | Intermediate soft glasses, ceramics | The glass sits between the 42 and 52 expansion values |
| NILO 52 / Alloy 52 | 50.5 % | ≈ 9.8 µm/m·°C | Soft lead and soda-lime glass | Sealing to soft glass: electronic tubes, lamps, feedthroughs, reed switches |
| NI-SPAN-C 902 | 42 % | Controlled modulus | — | Constant elastic modulus is needed, not constant length: springs, diaphragms |
Selection guide compiled by Jiangyin Jiangnan Metal Co., Ltd. CTE figures are mean values over the usual published ranges and are indicative for grade selection; use the full expansion curve for seal design. All grades listed are forged in this works.
09Where NILO 52 forgings are used
NILO 52 is specified where a part has to hold its dimensions, or hold a seal, while the temperature changes.
Glass-to-metal seals
Electronic tubes, automotive and industrial lamps, hermetic feedthroughs and specialty sealed devices using soft lead or soda-lime glass, in compression or eyelet brazed seal designs.
Rings · sleeves · bushings · flanges
Electrical and switchgear
Circuit breakers, magnetic reed switches, small transformers, and sealed contacts where linear expansion must stay controlled to about 525 °C.
Discs · bars · shafts
Thermostatic and regulating devices
Bimetal thermostat elements, temperature regulators and thermostatic bi-metal strip, where the alloy provides the low-expansion side of the pair.
Bars · strip blanks · discs
RF, radar and microwave
Cavity resonators, echo boxes and filters for mobile telephony, and magnetic shielding. The alloy has low dispersion, which suits high-frequency work.
Rings · housings · blocks
Precision instruments and metrology
Dimensionally stable instrument frames, optical device mounts, precision condenser blades, clock balance wheels and pendulum rods.
Bars · spindles · frames
Cryogenic and containment
Components that must keep strength and hardness at cryogenic limits, including containment and transfer hardware for liquefied gases.
Rolled rings · tube sheets · flanges
Valve and sealing hardware
Valve stems, seat rings, bodies, blocks and bonnets in ball, check, globe, gate and plug valves where a controlled-expansion seat is specified.
Seat rings · stems · bodies
Tooling for composites
Composite moulds and layup tooling for aerospace, where the tool must not expand away from the part during cure.
Plates · blocks · rolled rings
10Testing, certification and traceability
| Item | Standard / scope |
|---|---|
| Ultrasonic testing | EN 10228-3, SEP 1921 or ASTM A388, to the acceptance class stated on the order |
| Surface NDT | Magnetic particle or dye penetrant inspection on request |
| Chemical analysis | Ladle analysis on every heat; product analysis on request |
| Mechanical testing | Room-temperature tensile and hardness; impact testing where specified |
| Thermal expansion | Dilatometer testing of the expansion curve, available as an extra where the seal design depends on it |
| Metallography | Grain size and microstructure on request |
| Certification | EN 10204 3.1 as standard; EN 10204 3.2 countersigned by SGS, BV, TÜV or Lloyd's Register on request |
| Traceability | Heat number carried from ingot through forging, heat treatment, machining and packing |
| Quality system | ISO 9001:2015 |
Jiangyin Jiangnan Metal Co., Ltd. State the required certification level and NDT class with your enquiry. Both affect price and lead time, and both are difficult to add once material has shipped.
Designation lookup Tool 04
Type any designation from your drawing (UNS number, Werkstoff number, trade name, Chinese grade) to check whether it resolves to NILO 52 or to a different grade in the family.
11NILO 52 frequently asked questions
What is NILO 52?
NILO 52 is a controlled-expansion nickel-iron alloy containing a nominal 50.5 % nickel with the balance iron, supplied to ASTM F30 and designated UNS N14052. Its coefficient of thermal expansion is low and almost constant from room temperature to about 565 °C (1050 °F), which lets it be sealed to soft lead and soda-lime glasses and to some ceramics without cracking the seal. Jiangyin Jiangnan Metal Co., Ltd. open-die forges NILO 52 into rolled rings, discs, shafts, flanges, bars, sleeves, bushings and tube sheets.
What is NILO 52 equivalent to?
NILO 52 is equivalent to Alloy 52, UNS N14052, Werkstoff number 2.4478 (DIN 17745), ASTM F30 Class 2, AMS-I-23011 Class 2 (formerly MIL-I-23011C), AWS 093, and the Chinese grade 4J50. It is also marketed as Glass Sealing 52, Invar 52, Pernifer 50, 52 Alloy and N52. NILO is a registered trademark of Special Metals Corporation; material forged by Jiangyin Jiangnan Metal Co., Ltd. is correctly described as UNS N14052 to ASTM F30.
What is the chemical composition of NILO 52?
NILO 52 forged by Jiangyin Jiangnan Metal Co., Ltd. has a nominal nickel content of 50.5 % with iron as balance, carbon 0.05 % max, silicon 0.30 % max, sulfur 0.025 % max and chromium 0.025 % max. Nickel is adjusted by the melter within the specification so that the finished material meets the required thermal expansion curve rather than a fixed nickel number. The ladle analysis for every heat is stated on the EN 10204 3.1 mill certificate.
What is the thermal expansion coefficient of NILO 52?
The mean coefficient of thermal expansion of NILO 52 is approximately 9.8 µm/m·°C (5.4 µin/in·°F) over the range 25–450 °C, and the expansion curve stays almost constant up to about 565 °C (1050 °F). That value is deliberately matched to soft lead and soda-lime sealing glasses, whose expansion sits near 9.0–9.6 µm/m·°C.
Why is NILO 52 used for glass-to-metal seals?
A glass-to-metal seal fails when the metal and the glass shrink at different rates as the joint cools, because the difference puts the glass in tension and glass has almost no tensile strength. NILO 52 is used because its expansion curve tracks that of soft lead and soda-lime glasses closely enough over the sealing range that the residual stress stays compressive and low, giving a hermetic, crack-free seal in electronic tubes, lamps, feedthroughs and hermetic packages.
Can NILO 52 be forged, and in what shapes?
Yes. NILO 52 is hot forged in the range of about 1150 down to 900 °C. Jiangyin Jiangnan Metal Co., Ltd. supplies NILO 52 as seamless rolled rings from 200 to 2 500 mm outside diameter, forged discs to 1 800 mm diameter, shafts to 8 000 mm length, flanges, round bars from 25 to 500 mm diameter, sleeves, bushings, tube sheets and forged pipe, with single-piece weights up to about 8 000 kg. Cold working is avoided because residual cold work distorts the thermal expansion curve.
What heat treatment is applied to NILO 52 forgings?
NILO 52 is supplied and used in the annealed condition. Jiangyin Jiangnan Metal Co., Ltd. anneals NILO 52 forgings between 850 and 1000 °C, with soak time set by section thickness, followed by a controlled cool. Annealing removes the residual cold work and forging strain that would otherwise distort the coefficient of thermal expansion and destabilise glass seals.
What is the difference between NILO 52 and Invar 36?
Invar 36 contains about 36 % nickel and has a near-zero coefficient of thermal expansion of roughly 1.3 µm/m·°C, so it is chosen where a part must not move at all with temperature, such as precision instruments, optical benches and LNG containment. NILO 52 contains a nominal 50.5 % nickel and expands at about 9.8 µm/m·°C, which is not the lowest available but is deliberately matched to soft glass. Choose Invar 36 for dimensional stability and NILO 52 for sealing to glass.
What is the difference between NILO 52 and Alloy 42?
Both are ASTM F30 iron-nickel sealing alloys, but they are matched to different glasses. Alloy 42 contains about 42 % nickel and expands at roughly 4.5–5.3 µm/m·°C, matching hard borosilicate glasses, alumina ceramics and silicon. NILO 52 contains a nominal 50.5 % nickel and expands at about 9.8 µm/m·°C, matching soft lead and soda-lime glasses. Selecting the wrong one produces a seal in tension that cracks in service.
Who supplies open-die forged NILO 52?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges NILO 52 (Alloy 52, UNS N14052) to customer drawings as rolled rings, discs, shafts, flanges, bars, sleeves, bushings and tube sheets. The works operates 1, 3, 5 and 9 tonne forging hammers, a 5 000 tonne hydraulic press and 3 m and 6 m ring rolling mills. Quotations: sales@steelforgepieces.com or +86 189 2135 9659.
What certificates and testing are supplied with NILO 52 forgings?
Jiangyin Jiangnan Metal Co., Ltd. supplies NILO 52 forgings with an EN 10204 3.1 mill test certificate as standard, or an EN 10204 3.2 certificate countersigned by a third party such as SGS, BV, TÜV or Lloyd's Register on request. Forgings are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 to the acceptance class stated on the order, and chemical analysis, mechanical test results, heat treatment records and heat number traceability are reported on the certificate.
How do I get a quotation for NILO 52 forgings?
Send a drawing or the finished dimensions, the required quantity, the specification (ASTM F30 or an equivalent), the certification level (EN 10204 3.1 or 3.2) and any non-destructive testing class to sales@steelforgepieces.com, or call +86 189 2135 9659. Jiangyin Jiangnan Metal Co., Ltd. normally returns a quotation within 24 hours and can quote against a drawing, a part number or a plain dimensional description.
12Request a quotation
This builds the enquiry text for you, covering the information a forging shop needs before it can price a NILO 52 part. Nothing is sent from this page: you get text to copy, or an email draft in your own mail client.
RFQ builder Tool 05
Send the drawing. Get a price in 24 hours.
Jiangyin Jiangnan Metal Co., Ltd. has been open-die forging rings, discs, shafts and bars in Jiangyin, Jiangsu Province since 2008, in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, including the controlled-expansion grades. Single prototype pieces and production batches are both welcome.
Trademark notice. NILO® is a registered trademark of Special Metals Corporation. Pernifer® is a registered trademark of ThyssenKrupp VDM. Invar® and CarTech® Glass Sealing 52 are trademarks of their respective owners. Material produced by those companies and sold under those brand names is theirs. Material produced by Jiangyin Jiangnan Metal Co., Ltd. is correctly described as UNS N14052 / Alloy 52 to ASTM F30 / W.Nr. 2.4478, the same generic chemistry, manufactured independently. We are not affiliated with, sponsored by, or endorsed by any of the trademark holders named above, and we use their designations only to identify the equivalent grade.