Controlled expansion alloy / Open-die forgings
NILO 46 Forgings, UNS K94600 / ASTM F30 46 Alloy
NILO 46 is an iron-nickel controlled expansion alloy with a nominal nickel content of 46 percent and the balance iron. It is specified as 46 Alloy in ASTM F30 and numbered UNS K94600. The mean linear coefficient of thermal expansion is 7.5 µm/m·°C between 30 °C and 400 °C, which matches soft lead glass and soda-lime glass. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We produce NILO 46 forged rings, seamless rolled rings, flanges, round bars, discs, sleeves, bushings, tube sheets and shafts to customer drawing, supplied with EN 10204 3.1 or 3.2 certification.
Grade identity
- UNS
- K94600
- Standard
- ASTM F30
- Class
- MIL-I-23011 Cl 4
- Nickel
- 46.0 % nom.
- CTE 30-400 °C
- 7.5 µm/m·°C
- Curie point
- 460 °C
- Density
- 8.17 g/cm³
- Melting point
- 1427 °C
01Description
NILO 46 is one of the iron-nickel sealing alloys covered by ASTM F30, where it is listed as 46 Alloy. NILO is a trade name of Special Metals. The same composition is supplied under the names Pernifer 46, Glass Sealing 46 and Alloy 46. All of these refer to UNS K94600.
Nickel content controls the expansion curve in this family of alloys. At 46 percent nickel the curve is close to that of soft lead glass and soda-lime glass across the sealing range, so a seal between the two remains sound after cooling. For this reason the alloy is used in hermetic packages, vacuum devices, lamp components and thermostatic bimetals rather than in structural parts.
NILO 46 is ferromagnetic below its Curie temperature of 460 °C. Expansion stays flat below this temperature and rises above it, reaching 13.4 µm/m·°C at 1000 °C. In sealing applications the Curie point is normally taken as the upper service temperature.
02Equivalent names and specifications
| UNS number | K94600 |
|---|---|
| ASTM specification | ASTM F30, 46 Alloy |
| Military specification | MIL-I-23011 Class 4 |
| Aerospace specification | AMS I-23011 Class 4 |
| Trade names | NILO 46, Pernifer 46, CarTech Glass Sealing 46, Alloy 46, 46 Alloy, Ni46 |
| Alloy family | Iron-nickel controlled expansion / glass sealing alloy |
| Nominal composition | Fe - 46 Ni |
Source: ASTM F30-96 (2017). Trade names are the property of their respective owners. Jiangyin Jiangnan Metal Co., Ltd. supplies the equivalent UNS K94600 composition.
03Chemical composition
Ladle analysis and product analysis are both carried out and reported on the mill test certificate.
| Element | Symbol | ASTM F30 limit |
|---|---|---|
| Nickel | Ni | 46.00 nominal |
| Manganese | Mn | 0.80 max |
| Silicon | Si | 0.30 max |
| Carbon | C | 0.05 max |
| Chromium | Cr | 0.25 max |
| Aluminum | Al | 0.10 max |
| Phosphorus | P | 0.025 max |
| Sulfur | S | 0.025 max |
| Cobalt | Co | incidental element |
| Iron | Fe | Balance |
Source: ASTM F30-96 (2017), Table 1, 46 Alloy.
Where a drawing or purchase specification calls for limits tighter than ASTM F30, we quote and certify against the drawing. Please state any restricted element limits at enquiry stage.
04Thermal expansion
Expansion is approximately 7.5 µm/m·°C up to 400 °C. It begins to increase as the material approaches the Curie temperature of 460 °C and continues to rise at higher temperatures.
| Temperature range | CTE | Temperature range | CTE |
|---|---|---|---|
| 30 to 300 °C | 7.5 | 30 to 700 °C | 10.7 |
| 30 to 350 °C | 7.1 to 7.8 * | 30 to 800 °C | 11.6 |
| 30 to 400 °C | 7.5 | 30 to 900 °C | 12.5 |
| 30 to 500 °C | 8.2 to 8.9 * | 30 to 1000 °C | 13.4 |
| 30 to 600 °C | 9.8 |
Source: ASTM F30-96 (2017), Table X1.1, 46 Alloy. * Values marked with an asterisk are specification ranges from ASTM F30-96 (2017), Table 2.
05Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.17 g/cm³ | 0.295 lb/in³ |
| Specific gravity | 8.17 | 8.17 |
| Curie temperature | 460 °C | 860 °F |
| Melting point | 1427 °C | 2600 °F |
| Electrical resistivity | 47 µΩ·cm | 277 Ω·cir mil/ft |
| Thermal conductivity | 0.11 W/cm·°C (11 W/m·K) | 79.2 BTU·in/ft²·h·°F |
| Specific heat | 0.12 cal/g·°C (502 J/kg·K) | 0.12 BTU/lb·°F |
| Magnetic behaviour | Ferromagnetic below 460 °C, paramagnetic above | |
Source: ASTM F30-96 (2017) and published glass-to-metal sealing alloy data.
06Mechanical properties
Forgings are supplied in the annealed condition unless the drawing states otherwise.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 552 MPa | 80 ksi |
| Yield strength (0.2 % offset) | 242 MPa | 35 ksi |
| Elongation | 30 % in 50 mm | 30 % in 2 in |
| Hardness, annealed | 80 HRB | 80 HRB |
| Modulus of elasticity | 159 GPa | 23 × 10³ ksi |
Source: ASTM F30-96 (2017). Typical values for annealed material, not guaranteed minima. Guaranteed values are agreed per order and reported on the EN 10204 certificate.
Cold worked tempers
ASTM F30 also lists temper designations for cold worked strip and wire. These do not apply to forgings, which are supplied annealed. The values are given here for reference when converting a strip design to a forged part.
| Temper | Tensile, psi | Tensile, MPa |
|---|---|---|
| Annealed | 85,000 max | 586 max |
| Quarter hard | 90,000 to 115,000 | 621 to 793 |
| Half hard | 105,000 to 125,000 | 724 to 862 |
| Hard | 120,000 min | 827 min |
MPa values converted from psi and rounded to the nearest whole unit.
07Forged forms
The following forms are produced in NILO 46 to customer drawing.
Sizes are quoted against the drawing. Please send dimensions or a drawing file in PDF, DWG or STEP format together with the quantity required.
08Manufacturing and inspection
Melting
NILO 46 is melted by electric arc furnace, followed by vacuum oxygen decarburization and electroslag remelting. The ESR stage reduces non-metallic inclusions and centerline segregation. Both affect sealing performance and the consistency of the expansion coefficient across large sections.
Forging
Ingots are upset and drawn out on open dies. Ring blanks are punched and rolled on a radial-axial ring rolling mill to give circumferential grain flow. Forging ratio is controlled to break down the as-cast structure.
Heat treatment
Forgings are annealed. Stress relief is applied where the geometry requires it. Heat treatment records are issued per heat and appear on the certificate.
Non-destructive testing
Ultrasonic inspection to EN 10228-3, SEP 1921 or ASTM A388, to the acceptance class stated on the drawing. Dye penetrant and magnetic particle inspection are available where specified.
Documentation
Each shipment is supplied with an EN 10204 3.1 certificate covering heat number, ladle and product analysis, mechanical test results, heat treatment record, ultrasonic test report and dimensional report. EN 10204 3.2 certification witnessed by TUV, SGS, BV or Lloyd's Register is available. Please state this requirement at enquiry stage, as it affects delivery time.
09Applications
Glass-to-metal and hermetic sealing
- Seals to soft lead glass and soda-lime glass
- Hermetic feedthroughs and headers for electronic tubes and vacuum devices
- Electric lamp and bulb components
- Forged rings, sleeves and bushings used as sealing bodies and carriers
Thermostatic and temperature control
- Thermostatic bimetal strip components and bimetal thermostats
- Temperature regulators and thermostat rods
Telecommunications, RF and electronics
- Echo boxes and filter bodies for mobile telephony
- Radar and microwave cavity resonators
- Precision condenser blades, magnetic shielding, small transformer components, electrical resistors
- Housings, spacers and frames for electronic assemblies
Precision instruments
- Metrology devices and instrument frames
- Optical device mounts
- Clock balance wheels and pendulum components
- Positioning devices and composite mould tooling
Invar 36 rather than NILO 46 is normally specified for cryogenic and LNG applications, where near-zero expansion below 200 °C is required. Pressure-retaining valve components are normally supplied in a structural grade rather than a sealing alloy. Please advise the application and we will confirm the correct grade.
10Grade comparison
These grades differ mainly in nickel content, which is what sets the expansion curve.
| Grade | Nominal composition | Standard / UNS | Expansion | Typical use |
|---|---|---|---|---|
| Invar 36 / NILO 36 | Fe - 36 Ni | ASTM F1684, K93600 | Near zero below 200 °C | LNG, metrology, composite tooling |
| Alloy 42 / NILO 42 | Fe - 42 Ni | ASTM F30, K94100 | Low, below Alloy 46 | Lead frames, alumina ceramic and hard glass seals |
| NILO 46 | Fe - 46 Ni | ASTM F30, K94600 | 7.5 µm/m·°C, flat to 400 °C | Soft lead and soda-lime glass seals, bimetals |
| Alloy 48 / NILO 48 | Fe - 48 Ni | ASTM F30, K94800 | Higher than Alloy 46 | Soda-lime glass seals requiring a higher match |
| Kovar / NILO K | Fe - 29 Ni - 17 Co | ASTM F15, K94610 | Low, plateau to 450 °C | Borosilicate glass and ceramic seals |
Selection is made by matching the expansion curve of the metal to that of the glass or ceramic over the full service temperature range.
11Machining and welding
Machining
NILO 46 work hardens and produces a continuous chip. Use sharp positive rake tooling, rigid workholding with minimum overhang, reduced cutting speed, positive feed and ample coolant. Avoid dwelling and light finishing cuts, which run on the work hardened layer and accelerate tool wear.
Welding
TIG, electron beam and resistance welding are used with matching filler. Keep heat input low and clean the joint before welding. Carbon and sulfur contamination affects the expansion match and the vacuum tightness of any subsequent glass seal.
Surface condition
Sealing faces are normally oxidized before glass sealing. Please state on the order if a specific surface condition is required on delivery.
12Frequently asked questions
What is NILO 46?
NILO 46 is an iron-nickel controlled expansion alloy with a nominal nickel content of 46 percent and the balance iron. It is specified as 46 Alloy in ASTM F30 and numbered UNS K94600. Its coefficient of thermal expansion matches soft lead glass and soda-lime glass, so it is used for glass-to-metal seals, hermetic electronic packages and thermostatic bimetal elements. Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory in Jiangyin, Jiangsu Province, China, supplies NILO 46 as forged rings, seamless rolled rings, flanges, bars, discs, sleeves and shafts.
What is the UNS number for NILO 46?
The UNS number for NILO 46 is UNS K94600. The same material is designated 46 Alloy in ASTM F30 and Class 4 in MIL-I-23011 and AMS I-23011.
What is the chemical composition of NILO 46?
To ASTM F30-96 (2017) Table 1 for 46 Alloy: nickel 46.00 % nominal, manganese 0.80 % max, silicon 0.30 % max, carbon 0.05 % max, chromium 0.25 % max, phosphorus 0.025 % max, sulfur 0.025 % max, aluminum 0.10 % max, cobalt present as an incidental element, iron remainder.
What is the thermal expansion coefficient of NILO 46?
The mean linear coefficient of thermal expansion of NILO 46 (UNS K94600) is 7.5 µm/m·°C over 30 to 300 °C and over 30 to 400 °C. ASTM F30 Table 2 specifies 7.1 to 7.8 over 30 to 350 °C and 8.2 to 8.9 over 30 to 500 °C. Above the Curie temperature of 460 °C the values increase: 9.8 over 30 to 600 °C, 10.7 over 30 to 700 °C, 11.6 over 30 to 800 °C, 12.5 over 30 to 900 °C and 13.4 over 30 to 1000 °C.
What are the physical properties of NILO 46?
NILO 46 (UNS K94600) has a density of 8.17 g/cm³ (0.295 lb/in³), a Curie temperature of 460 °C (860 °F), a melting point of 1427 °C (2600 °F), an electrical resistivity of 47 µΩ·cm, a thermal conductivity of 0.11 W/cm·°C and a specific heat of 0.12 cal/g·°C. Source: ASTM F30-96 (2017).
What are the mechanical properties of NILO 46?
In the annealed condition NILO 46 (UNS K94600) has a typical tensile strength of 552 MPa (80 ksi), a typical yield strength of 242 MPa (35 ksi) at 0.2 % offset, an elongation of 30 % in 50 mm, a hardness of about 80 HRB and a modulus of elasticity of about 159 GPa. Jiangyin Jiangnan Metal Co., Ltd. supplies NILO 46 forgings annealed unless the drawing states otherwise, and reports the tested values on the EN 10204 certificate.
What is the difference between NILO 46 and Invar 36?
Invar 36 contains about 36 % nickel and has a near-zero coefficient of thermal expansion below approximately 200 °C. It is specified where dimensional stability is the requirement, such as LNG containment, precision tooling and metrology equipment. NILO 46 contains 46 % nickel and has a higher and flatter expansion of about 7.5 µm/m·°C, which matches soft lead glass and soda-lime glass. Invar 36 is used for minimum movement and NILO 46 for a matched glass seal.
Is NILO 46 magnetic?
Yes. NILO 46 is ferromagnetic at room temperature and loses its ferromagnetism above its Curie temperature of approximately 460 °C (860 °F). The increase in thermal expansion above 460 °C is a result of this magnetic transition.
Can NILO 46 be supplied as seamless rolled rings?
Yes. Jiangyin Jiangnan Metal Co., Ltd. produces NILO 46 seamless rolled rings by upsetting, punching and radial-axial ring rolling, which gives circumferential grain flow. Rings are supplied rough machined or finish machined to the customer drawing and are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388.
What forged forms of NILO 46 are available?
Jiangyin Jiangnan Metal Co., Ltd. produces NILO 46 (UNS K94600) as seamless rolled rings, forged rings, forged flanges, round bars, discs and disks, sleeves and bushings, hollow bars and tubes, tube sheets, shafts and spindles, and blocks and blanks. All forms are made to the customer drawing and quoted against dimensions and quantity.
What material certificate is supplied with NILO 46 forgings?
Each NILO 46 forging is supplied with an EN 10204 3.1 mill test certificate issued by Jiangyin Jiangnan Metal Co., Ltd. covering heat number, ladle and product chemical analysis, mechanical test results, heat treatment record, ultrasonic test report and dimensional report. EN 10204 3.2 certification witnessed by a third party such as TUV, SGS, BV or Lloyd's Register is available on request.
How is NILO 46 melted before forging?
NILO 46 for forging is melted by electric arc furnace, followed by vacuum oxygen decarburization and electroslag remelting (EAF + VOD + ESR). The ESR stage reduces non-metallic inclusions and centerline segregation, both of which affect sealing performance and the consistency of the expansion coefficient across large sections.
Can NILO 46 be machined and welded?
NILO 46 work hardens and produces a continuous chip. Use sharp positive rake tooling, rigid workholding, reduced cutting speed, positive feed and ample coolant. It can be joined by TIG, electron beam and resistance welding with matching filler. Keep heat input low and clean the joint before welding, since carbon and sulfur contamination affects the expansion match and the vacuum tightness of any subsequent glass seal.
Who supplies NILO 46 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, that manufactures NILO 46 (UNS K94600) forgings to customer drawing. Enquiries: sales@steelforgepieces.com, telephone +86-189-2135-9659.
What is the minimum order quantity and delivery time?
Minimum order quantity and delivery time depend on size, weight, machining scope and certification requirements. Send the drawing and quantity to sales@steelforgepieces.com and both will be confirmed with the quotation.
Request a NILO 46 forging quotation
Send a drawing, or dimensions and quantity. We reply with price, weight and delivery time, normally within one working day.
- Manufacturer
- Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory - Factory address
- No.1 Chengxiqiao Road
Zhouzhuang Town, Jiangyin City
Jiangsu Province, China - Telephone / WhatsApp / WeChat
- +86 189 2135 9659
- Please include
- Grade, drawing or dimensions, quantity, heat treatment condition, ultrasonic class, certificate type
- Delivery terms
- Worldwide. EXW, FOB Shanghai or CIF
Technical data reproduced from ASTM F30-96 (2017). Values are given for guidance and are not a guarantee of the properties of any particular delivery. Contractual values are those stated on the mill test certificate for the heat supplied. Page updated 25 August 2026.