Nickel alloy forgings / UNS K94100 / W.Nr. 1.3917
NAS 42 Forgings Fe-42Ni controlled-expansion alloy. Rings, bars, discs, flanges, sleeves and shafts forged to drawing.
NAS 42 is a 42 % nickel-iron alloy with a coefficient of thermal expansion close to that of silicon, ceramic and glass. It is used for semiconductor lead frames, glass-to-metal seals, thermostat rods and aerospace composite tooling. Jiangyin Jiangnan Metal Co., Ltd. forges NAS 42 to customer drawings at its works in Jiangyin, Jiangsu Province, China.
- Grade
- NAS 42
- UNS
- K94100
- W.Nr. / EN
- 1.3917
- Nickel
- 40.0–43.0%
- CTE 20–100 °C
- 5.3×10⁻⁶/K
- Density
- 8.11g/cm³
- Melting point
- 1435°C
- Curie point
- 370°C
Summary
NAS 42 is a controlled-expansion alloy containing 40 to 43 % nickel with the balance iron. It carries the designations UNS K94100 and W.Nr. 1.3917. Its coefficient of thermal expansion is low and nominally constant from room temperature to about 300 °C (572 °F). NAS 42 is the mill designation used by Nippon Yakin Kogyo. The same alloy is sold elsewhere under the names Alloy 42, NILO 42, Invar 42, Pernifer 42, Dilaton 42 and Glass Sealing 42.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The company forges NAS 42 into seamless rolled rings, round bars, discs, flanges, sleeves, bushings, shafts, tube sheets and hollow forgings to customer drawings. Parts are supplied annealed, ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388, and certified to EN 10204 3.1 or 3.2. For quotations contact sales@steelforgepieces.com or +86 189 2135 9659.
Thermal expansion / calculated comparison
Growth of a 1 000 mm bar heated from 20 °C to 300 °C
Chemistry / weight %
Chemical composition of NAS 42
NAS 42 is a binary iron-nickel alloy. Nickel is held between 40.0 % and 43.0 % and iron makes up the balance. Carbon, phosphorus and sulphur are restricted because they affect expansion behaviour and the cleanliness required for glass sealing.
| Limit | C | Si | Mn | P | S | Ni | Cr | Fe |
|---|---|---|---|---|---|---|---|---|
| Min | – | – | – | – | – | 40.0 | – | Balance |
| Max | 0.03 | 0.30 | 0.80 | 0.025 | 0.025 | 43.0 | 0.25 |
ASTM F30 Alloy 42, the nearest written specification, is slightly wider: C 0.05 % max, P 0.03 % max, S 0.03 % max, Al 0.10 % max. State which specification governs the part and the material is forged to that chemistry.
Melting route
The NAS 42 material used for these forgings is melted by EAF plus VOD and then electroslag remelted (ESR). Remelting reduces inclusions and segregation, which keeps the expansion coefficient uniform through a heavy forged section rather than only near the surface.
Physical properties / typical values, annealed
NAS 42 physical and mechanical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.11 g/cm³ | 0.293 lb/in³ |
| Melting point | 1435 °C | 2615 °F |
| Curie / inflection point | 370 °C | 700 °F |
| Thermal conductivity | 10.5 W/m·K | 72.8 BTU·in/ft²·h·°F |
| CTE, 20 to 100 °C | 5.3 ×10⁻⁶/K | 2.9 ×10⁻⁶/°F |
| CTE, 20 to 300 °C | 4.5–6.5 ×10⁻⁶/K | 2.5–3.6 ×10⁻⁶/°F |
| Tensile strength, annealed | 600 MPa max | 87 ksi max |
| Useful service range | to 300 °C | to 572 °F |
| Magnetic response | Ferromagnetic below the Curie point | |
Values are typical and intended for design screening. They are not guaranteed minima. The values applying to a specific order are those recorded on the EN 10204 certificate issued against the heat.
Service limit and the inflection point
NAS 42 retains its low expansion only below the Curie point of about 370 °C. Above that temperature the alloy loses its ferromagnetic ordering, the Invar effect disappears and expansion rises toward that of ordinary steel. NAS 42 components are normally designed for service below 300 °C.
Effect of cold work
Residual cold work distorts the expansion coefficient of iron-nickel alloys. NAS 42 parts are finished and used in the annealed condition. If a part is straightened, coined or heavily machined after annealing, it should be re-annealed before the expansion coefficient can be relied on.
Cross-reference / equivalent designations
NAS 42 equivalent grades
This alloy is ordered under a number of different names. The table below lists the designations commonly cross-referenced to NAS 42. Composition windows differ slightly between mills and specifications, so the governing specification should be stated on the purchase order.
| System or owner | Designation | Note |
|---|---|---|
| Nippon Yakin Kogyo | NAS 42 | Mill designation, Fe-42Ni |
| UNS | K94100 | Primary international reference |
| EN / DIN | 1.3917, Ni42 | Werkstoffnummer |
| ASTM | F30 Alloy 42, F1684, B753 | F30 covers glass-sealing alloys, B753 lead frames |
| Special Metals | NILO 42 | Trade name |
| VDM Metals | Pernifer 42, Pernifer 40 | Trade name |
| Carpenter | Low Expansion 42 | Trade name |
| Trade names | Alloy 42, Invar 42, Dilaton 42, Glass Sealing 42, FeNi42 | Same 42 % Ni family |
| JIS | None | No JIS grade exists for this alloy |
Related controlled-expansion grades also forged here: Invar 36, which has the lowest expansion of the group at about 1.3 ×10⁻⁶/K, Invar 42, Alloy 48 and Ni-Span-C Alloy 902.
Process / open-die forging and ring rolling
Forging and heat treatment of NAS 42
NAS 42 forges readily but has a narrower working range than carbon steel and work hardens quickly. Reductions are planned so that forging finishes before the metal falls out of range. Typical practice is set out below.
| Operation | Temperature | Hold and cooling |
|---|---|---|
| Heating for forging | 1120–1180 °C | Soak to through-heat the billet |
| Finish forging above | 900 °C | Reheat rather than force a cold finish |
| Annealing | 850–1000 °C | About 30 min per 25 mm of section, air or water cool |
| Atmosphere | – | Protective or bright anneal to avoid scale and nickel depletion |
| Delivery condition | – | Annealed, as-forged or rough-machined to drawing |
Forms produced in NAS 42
- Seamless rolled ringsRing rolled rather than cut from plate, so that grain flow follows the circumference.
- Forged round bars and shaftsSolid bars, stepped shafts, spindles and thermostat rod stock.
- Forged discs and disksSolid and bored blanks, including plates for composite tooling.
- Forged flangesBlind, weld-neck, slip-on and special profiles to drawing.
- Sleeves, bushings and hollow barsTrepanned or mandrel forged, with the bore machined to size.
- Tube sheets and forged blocksHeavy plate-form forgings, drilled to the customer layout on request.
Sizes are produced to drawing. Send a drawing for confirmation of feasibility, weight and price.
Applications / by industry
What NAS 42 forgings are used for
In each of these applications the alloy is chosen because an adjacent component, whether silicon, ceramic, glass or carbon-fibre composite, has a low expansion coefficient that the metal beside it has to match.
- Semiconductor and electronicsLead-frame tooling, metal-mask and vibrating-plate tooling, and precision fixtures that must hold dimension through thermal cycling.
- Glass-to-metal and ceramic-to-metal sealsHermetic feed-throughs, lamp and vacuum-device components, and alumina-to-metal seals in sensors and connectors.
- Aerospace composite toolingForged plates and rings for autoclave moulds, where the mould has to track the expansion of the carbon-fibre part rather than that of steel.
- Thermostats and controlsThermostat rods and the low-expansion side of bimetal strip, circuit breakers and temperature regulators.
- Cryogenic and LNG serviceContainment and transfer-line components where thermal contraction must remain small and predictable.
- Precision instrumentsDimensionally stable frames, optical mounts, metrology fixtures, and microwave and RF cavity resonators.
- Valve componentsStems, seat rings, bodies and blocks where seal clearance has to hold across a temperature swing.
- Positioning and motion hardwareSpacers, frames and locating devices in equipment that is calibrated cold and run warm.
Quality / EN 10228-3, SEP 1921, ASTM A388, EN 10204
Testing, inspection and certification
NAS 42 forgings from Jiangyin Jiangnan Metal are supplied with a full document package. State the acceptance class required and testing is carried out to it.
- Chemical analysis. Ladle and product analysis on every heat.
- Ultrasonic testing. To EN 10228-3, SEP 1921 or ASTM A388, acceptance class as specified on the order.
- Mechanical testing. Tensile, hardness and, where required, impact testing.
- Thermal expansion testing. Dilatometry over the stated temperature range, on request.
- Dimensional inspection. Against the drawing, with a report.
- Certification. EN 10204 3.1 mill certificate, or EN 10204 3.2 witnessed by a third party such as SGS, BV, TUV or Lloyd's.
- Surface examination. Magnetic particle or dye penetrant where the drawing calls for it.
Ordering / information required
How to order NAS 42 forgings
- Send the drawing. PDF, DWG or STEP. A dimensioned sketch is sufficient for a budget price.
- State the specification. NAS 42, ASTM F30 Alloy 42, UNS K94100 or your own works specification, whichever governs the order.
- State the test and certificate requirements. Ultrasonic testing standard and acceptance class, EN 10204 3.1 or 3.2, and any third-party witness.
- State quantity and delivery condition. As-forged, annealed, rough-machined or finish-machined, with the machining allowance to be left on.
- Receive the quotation. Price, weight, lead time and the proposed forging route follow, normally within one working day.
Questions
NAS 42 frequently asked questions
What is NAS 42?
NAS 42 is a controlled-expansion alloy containing 40 to 43 % nickel with the balance iron, designated UNS K94100 and W.Nr. 1.3917. Its coefficient of thermal expansion is close to that of silicon, ceramic and glass, which makes it suitable for lead frames, hermetic seals and any assembly where a metal part has to expand at the same rate as a non-metal part.
What is the coefficient of thermal expansion of NAS 42?
The mean coefficient of thermal expansion of NAS 42 is about 5.3 × 10⁻⁶/K between 20 °C and 100 °C, and typically falls in the range 4.5 to 6.5 × 10⁻⁶/K between 20 °C and 300 °C. A 1 000 mm NAS 42 bar heated from 20 °C to 300 °C grows about 1.5 mm, against about 4.8 mm for 304 stainless steel.
Is NAS 42 the same as Alloy 42, Invar 42 or NILO 42?
They are the same alloy family and are routinely cross-referenced. NAS 42 is Nippon Yakin Kogyo's mill designation, while Alloy 42, NILO 42, Invar 42, Pernifer 42, Dilaton 42 and Glass Sealing 42 are trade or generic names for 42 % nickel-iron. Composition windows differ slightly between specifications, so state the governing specification on the order rather than relying on the trade name alone.
Does NAS 42 have a JIS equivalent?
No. There is no JIS grade for this alloy. NAS 42 is a mill designation, and the usual written specifications are ASTM F30 for glass-sealing alloys, ASTM F1684 for iron-nickel controlled-expansion alloys and ASTM B753 for lead-frame alloys, together with UNS K94100 and W.Nr. 1.3917.
How is NAS 42 heat treated after forging?
NAS 42 is annealed between 850 °C and 1000 °C in a protective atmosphere, held roughly 30 minutes per 25 mm of section, then air or water cooled. Annealing is essential because residual cold work distorts the expansion coefficient, so NAS 42 parts must be finished and used in the annealed condition.
Is NAS 42 magnetic?
Yes. NAS 42 is ferromagnetic below its Curie point of about 370 °C. Above that temperature it loses magnetic ordering and its thermal expansion rises toward that of ordinary steel, which is why NAS 42 components are designed for service below 300 °C.
What forms of NAS 42 forgings can be supplied?
Jiangyin Jiangnan Metal supplies NAS 42 as seamless rolled rings, forged round bars, shafts and spindles, discs and disks, flanges, sleeves, bushings, hollow bars, tube sheets and forged blocks. All sizes are made to the customer's drawing rather than sold from a fixed stock range.
What testing and certification comes with NAS 42 forgings?
Standard supply includes chemical analysis, mechanical testing and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, with an EN 10204 3.1 mill certificate. EN 10204 3.2 certificates witnessed by SGS, BV, TUV or Lloyd's are available on request, as are dilatometry reports covering the customer's temperature range.
Who supplies NAS 42 open-die 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, producing NAS 42 and other controlled-expansion, nickel and stainless forgings to customer drawings. Contact sales@steelforgepieces.com or +86 189 2135 9659.
Can NAS 42 be welded and machined?
Yes. NAS 42 is weldable by TIG, MIG and resistance methods, normally with a matching filler, and welds should be annealed afterwards where expansion behaviour matters across the joint. It machines in a similar way to austenitic stainless steel. The alloy work hardens, so sharp tooling, positive rake, rigid setups and heavy continuous cuts give the best results.
Manufacturer
Jiangyin Jiangnan Metal Co., Ltd.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, on the south bank of the Yangtze. The company forges nickel alloys, stainless steels, tool steels, alloy steels and carbon steels into rings, bars, discs, flanges, shafts, sleeves and tube sheets, all produced to customer drawings.
Controlled-expansion grades such as NAS 42, Invar 36 and Alloy 48 require close process control. That means remelted stock, controlled finish forging temperatures, protective-atmosphere annealing, and dilatometry where the customer requires the expansion curve in writing.
Goods are shipped worldwide from Shanghai and Zhangjiagang ports. Quotations are issued in USD, EUR or RMB.
- Company
- Jiangyin Jiangnan Metal Co., Ltd.
- Business
- Open-die forging factory, seamless rolled rings
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone
- +86 189 2135 9659
- sales@steelforgepieces.com
- Website
- www.steelforgepieces.com
- Materials
- Nickel alloys, stainless steel, tool steel, alloy steel, carbon steel
Document reference
Jiangyin Jiangnan Metal Co., Ltd. "NAS 42 Forgings, Fe-42Ni Controlled Expansion Alloy (UNS K94100)." steelforgepieces.com, updated 21 August 2026. https://www.steelforgepieces.com/Nickel-Alloy/NAS-42.html