01 / MaterialWhat FeNi29Co17 is, and why it is specified
FeNi29Co17 is specified for the shape of its expansion curve rather than for low expansion. The curve tracks borosilicate glass from sub-zero temperatures up to an inflection point near 450 °C, and that match is the whole reason the alloy exists.
The alloy is vacuum melted and its chemistry held inside narrow limits. Position and flatness of the expansion curve depend directly on the nickel and cobalt balance, and a composition that drifts a few tenths of a percent off nominal moves the curve far enough to put a hermetic seal into tension on cooling. For this reason FeNi29Co17 is bought against a named specification with a test certificate rather than against a general iron-nickel-cobalt description.
Two properties carry the application. The first is the matched expansion described above. The second is the oxide film: heated in air at 650 to 700 °C the alloy grows a thin, adherent, dark grey oxide that molten glass wets and chemically bonds to. If that oxide is stripped by over-cleaning, contaminated by carbon pickup during machining, or never formed because the part was annealed in the wrong atmosphere, the seal will fail even though the expansion match is correct.
Where forged FeNi29Co17 is specified instead of sheet or bar stock
Most FeNi29Co17 is supplied as thin strip and small-diameter bar for lead frames and headers. Forgings are specified when the part is too large, too thick or too highly stressed for mill product:
- Large vacuum and microwave envelopes. Ring and flange sections for power tubes, travelling-wave tubes, klystrons and X-ray tube housings. A seamless rolled ring keeps a weld seam out of the seal path.
- Ceramic-to-metal feedthrough bodies. Forged blanks machined into flanges and housings for high-voltage and high-vacuum feedthroughs.
- Instrument and optical structures. Forged discs and frames where dimensional stability across a wide temperature band governs the design.
- Bimetal and thermostatic components. Forged bar and disc stock for positioning devices and temperature regulators.
- Composite tooling. Forged blanks for aerospace layup moulds whose expansion has to be matched to the laminate.
Check the specification before ordering. If the requirement is minimum dimensional movement, FeNi29Co17 is the wrong alloy and Invar 36 at roughly 1.5 x 10-6 /K is the correct choice. FeNi29Co17 matches glass and ceramic; it does not minimise expansion. This is the error we see most often on enquiries for this grade.
02 / DesignationsEquivalent grades, standards and trade names
FeNi29Co17 appears under a large number of national designations and proprietary trade names. All of the following describe the same nominal Fe-29Ni-17Co controlled-expansion alloy. Composition limits and test requirements differ slightly between specifications, so name the governing standard on the order.
| Region or body | Designation | Notes |
|---|---|---|
| Germany | FeNi29Co17, W.Nr 1.3981 | DIN 17745, SEW 385 |
| USA, UNS | K94610 | Wrought product |
| USA, ASTM | ASTM F15 | Iron-nickel-cobalt sealing alloy |
| USA, AMS | AMS 7727 | Bars and forgings. Cite this one for forged product |
| USA, AMS | AMS 7726 / AMS 7728 | Wire / sheet, strip and plate |
| USA, military | MIL-I-23011 Class 1 | Legacy designation |
| China | 4J29 | GB/T 15018 |
| France | NF A54-301 / A54-302 | AFNOR, FeNi29Co17 |
| United Kingdom | BS HR 601 | Also sold as Nilo K |
| Japan | JIS H 4551, CCMA 6 | Fe-Ni-Co sealing alloy |
| ISO | BS ISO 19960 | Glass-sealing alloys |
| Trade names | Kovar, Nilo K, Pernifer 2918, Rodar, Dilver P1, Vacon 12, Nicosel, Telcoseal, Ulbravar | Proprietary names within the same alloy family |
Kovar is a registered trademark of CRS Holdings Inc. and Carpenter Technology Corporation. Nilo is a trademark of Special Metals Corporation. We are not affiliated with either company. The names are listed so that buyers can match the grade they have been asked to source.
03 / ChemistryChemical composition of FeNi29Co17
Two limit sets are in common use. DIN 17745 defines the broader envelope. ASTM F15 material is normally supplied to tighter aim values, because narrow chemistry control is what keeps the expansion curve inside the sealing window. Unless the drawing states otherwise, we supply against DIN 17745 limits with ASTM F15 aim chemistry.
| Element | DIN 17745 limits | ASTM F15 typical aim | Function |
|---|---|---|---|
| Nickel (Ni) | 28.0 to 30.0 | 29.00 | Sets the position of the expansion curve |
| Cobalt (Co) | 16.0 to 18.0 | 17.00 | Raises the Curie point and flattens the curve |
| Iron (Fe) | Balance | Balance | Matrix |
| Carbon (C) | 0.05 max | 0.02 max | Held low. Carbon degasses during sealing and blows the joint |
| Silicon (Si) | 0.30 max | 0.20 | Deoxidiser. Excess harms oxide adhesion |
| Manganese (Mn) | 0.50 max | 0.30 | Deoxidiser, sulphur control |
| Phosphorus (P) | 0.02 max | 0.02 max | Residual |
| Sulphur (S) | 0.02 max | 0.02 max | Residual. Harmful to hot workability |
| Aluminium (Al) | 0.10 max | 0.05 max | Residual. Forms a tenacious oxide, so held low |
| Chromium (Cr) | 0.20 max | 0.20 max | Residual. Degrades glass wetting |
| Copper (Cu) | 0.20 max | 0.20 max | Residual |
| Molybdenum (Mo) | 0.20 max | 0.20 max | Residual |
Residual element limits vary between specifications and between mills. Where a seal-critical application restricts Al, Cr or Ti further, state the limits on the enquiry so that billet can be sourced to match before forging.
Melting route
Our standard FeNi29Co17 forging stock is produced by EAF + VOD + ESR: electric arc melting, vacuum oxygen decarburisation, then electroslag remelting. ESR provides the cleanliness and directional solidification required in a forging billet. Where the application calls for vacuum-melted material to the letter of ASTM F15, typically thin-section sealing parts, VIM + VAR billet can be sourced on request. State this at enquiry stage, since it affects both price and lead time.
04 / PhysicalPhysical properties
Values below are typical for annealed FeNi29Co17 and are the figures normally used for heat transfer, resistance and mass calculations. They are typical published values rather than guaranteed minima. The certificate issued with a forging carries the values measured on that heat.
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.36 g/cm³ | 0.302 lb/in³ |
| Specific gravity | 8.36 | 8.36 |
| Melting point | 1449 °C | 2640 °F |
| Curie temperature | 435 °C | 815 °F |
| Thermal conductivity at 20 °C | 17.3 W/(m·K) | 120 BTU·in/hr·ft²·°F |
| Specific heat at 20 °C | approx. 460 J/(kg·K) | 0.11 BTU/lb·°F |
| Electrical resistivity at 20 °C | approx. 49 µΩ·cm | 294 Ω·cmil/ft |
| Modulus of elasticity | approx. 138 GPa | 20 x 10³ ksi |
| Magnetic condition | Ferromagnetic below 435 °C, paramagnetic above | |
| Low-temperature stability | No transformation after 4 h at -80 °C when correctly annealed | |
Magnetic permeability depends on heat treatment. The softer the anneal, the higher the permeability and the lower the hysteresis loss. Permeability is not a standard test on forgings, so specify it if it is a design parameter.
05 / MechanicalMechanical properties
FeNi29Co17 is a moderate-strength alloy that behaves austenitically. Strength is rarely the selection criterion, and forgings are normally supplied annealed so that acceptance turns on expansion behaviour and anneal condition rather than on tensile figures.
| Property | Typical value | Imperial |
|---|---|---|
| Tensile strength, Rm | approx. 518 MPa | 75 ksi |
| Yield strength, Rp0.2 | approx. 276 MPa | 40 ksi |
| Elongation, A | approx. 30 % | 30 % in 2 in |
| Hardness, annealed | approx. 150 HV | approx. 80 HRB |
| Modulus of elasticity, E | approx. 138 GPa | 20 x 10³ ksi |
| Grain size | ASTM 5 to 8 typical after final anneal. Specify if controlled | |
Cold work raises strength substantially and lowers permeability, and it also shifts the expansion curve. Sealing parts should always be annealed after forming and never shipped in the cold-worked condition.
06 / ExpansionThermal expansion data
Below roughly 450 °C the mean expansion coefficient of FeNi29Co17 sits in a narrow band around 5 x 10-6 /K. Above that point the alloy has passed its Curie temperature, loses the magnetic contribution to the lattice, and expansion climbs steeply.
| Temperature range | x10-6 /K | x10-6 /°F | Regime |
|---|---|---|---|
| 25 to 100 °C | 5.85 | 3.25 | Sealing range |
| 25 to 200 °C | 5.20 | 2.89 | Sealing range |
| 25 to 300 °C | 5.13 | 2.85 | Sealing range |
| 25 to 350 °C | 4.90 | 2.72 | Sealing range, minimum |
| 25 to 400 °C | 5.06 | 2.81 | Sealing range |
| 25 to 450 °C | 5.26 | 2.92 | Inflection point |
| 25 to 500 °C | 6.14 | 3.41 | Above inflection |
| 25 to 600 °C | 7.81 | 4.34 | Above inflection |
| 25 to 700 °C | 9.11 | 5.06 | Above inflection |
| 25 to 800 °C | 10.31 | 5.73 | Above inflection |
| 25 to 900 °C | 11.25 | 6.25 | Above inflection |
Values apply to material annealed 1 h at 900 °C plus 15 min at 1099 °C in hydrogen and cooled to room temperature within 1 h. Different anneals produce measurably different curves, which is why the anneal is specified rather than left to the shop.
Glasses and ceramics FeNi29Co17 seals to
07 / Product formsFeNi29Co17 forged product forms and size range
Everything on this page is made to drawing. FeNi29Co17 is too expensive to hold as finished shapes, so there is no stock catalogue for this grade. Send the geometry and we will confirm whether we can forge it.
| Form | Typical size range | Notes |
|---|---|---|
| Seamless rolled rings | OD 150 to 2500 mm, H 30 to 600 mm | Ring rolled, no weld seam in the seal path |
| Open-die forged rings | OD 100 to 1500 mm | Upset and punched, for short runs and heavy walls |
| Forged flanges | OD 100 to 1800 mm | Blank or machined to drawing |
| Discs and blanks | dia. 80 to 1500 mm, t 20 to 400 mm | Upset discs for machined housings |
| Round bars | dia. 40 to 600 mm | Forged, peeled or rough turned |
| Sleeves and bushings | OD 100 to 1200 mm | Hollow forged, bored |
| Tube sheets | dia. up to 2000 mm | Solid forged plate |
| Shafts and spindles | dia. 60 to 500 mm, L up to 4000 mm | Stepped or plain |
| Hollow forgings | OD 150 to 1200 mm | Trepanned or expanded |
Ranges are indicative. Dimensions outside these figures are often still possible, and an unusual shape needs a look at the actual geometry before we can answer.
Delivery conditions
- As forged. Descaled, with forging allowance on all machined faces.
- Rough machined. Turned to a stated allowance, typically 3 to 6 mm per side, so that the part can be ultrasonically inspected on clean surfaces.
- Finish machined. To your drawing, including bores, faces and sealing surfaces.
- Annealed. Standard for this grade. Hydrogen or cracked-ammonia anneal on request for sealing-critical parts.
08 / ProcessHow we forge FeNi29Co17
FeNi29Co17 forges like a soft austenitic alloy. It is sensitive to two things: the working temperature window and surface contamination. The route below is what we run unless a drawing calls for something else.
1. Billet and traceability
ESR billet is received with its own mill certificate, and the heat number is transferred to every piece cut from it. Heat number, our internal job number and the customer order number stay stamped or tagged on the forging from cut-off to shipment, so the certificate that arrives with the part traces back to the ingot.
2. Heating
Billet is heated in a controlled-atmosphere or clean gas-fired furnace. Sulphur-bearing fuel is avoided. Sulphur pickup at forging temperature causes hot shortness and spoils the surface for later sealing work.
3. Forging
Start temperature is nominally 1150 °C, with finishing above roughly 900 °C. Working below the finish temperature risks cracking. Working above the start temperature coarsens the grain and reduces the properties obtained after annealing. Reduction is planned to give a worked structure through the full section rather than only at the surface. On heavy rings an under-reduced core shows up later as a rejected ultrasonic indication.
4. Ring rolling
Rings are upset, punched and rolled on the ring mill to give continuous circumferential grain flow. On vacuum-envelope and feedthrough work this gives better mechanical integrity and keeps a weld out of the seal path, which a fabricated ring cannot do.
5. Heat treatment
Forgings are annealed after forging. Section 09 covers the sealing-specific anneal and oxidation practice.
6. Machining and inspection
Rough turning, ultrasonic inspection, dimensional check, then final machining if the part is ordered finish machined. Tooling and coolant used on FeNi29Co17 destined for glass sealing are kept separate from carbon-steel work to avoid iron and carbon pickup on the surfaces that will later carry the oxide film.
09 / Heat treatmentAnnealing, hydrogen firing and oxide preparation
Heat treatment on this alloy sets both the expansion curve and the surface chemistry that the glass has to bond to, so it is specified in detail rather than left open.
Standard anneal
Heat to 850 to 1000 °C, preferably in hydrogen or cracked ammonia, and cool in the protective atmosphere. This is the normal supply condition for forgings that will be machined before sealing.
Degas and wet-hydrogen anneal for sealing parts
Degreased, fully machined parts are degassed and annealed in wet hydrogen, meaning hydrogen bubbled through water at room temperature, in the range 838 to 1099 °C. Hold time runs from roughly 2 hours at the low end of that range down to about 20 minutes at the high end. Parts are then transferred to a cooling zone under the same atmosphere and held until below 299 °C before being removed to air.
The purpose is decarburisation and degassing. Carbon left in the surface comes out as gas during the glass seal and blows a bubble through the joint. Guard against carbon pickup from the furnace atmosphere, from cutting fluid residue and from handling with oily gloves.
Growing the sealing oxide
An oxide film is required for metal-to-hard-glass sealing, and the best film is thin and tightly adhering. Heat the parts in ordinary ambient atmosphere at 650 to 700 °C for long enough to develop a dark grey to slightly brown film. Thick black scale is a defect rather than a better oxide, because it flakes and the seal then fails at the flake.
Order of operations. Machine, degrease, wet-hydrogen anneal, oxidise, then seal. Growing the oxide before final machining wastes it, and sealing without the wet-hydrogen step is the usual cause of bubbled joints in production.
Forging and hot-working temperatures
| Operation | Temperature | Atmosphere |
|---|---|---|
| Forging start | approx. 1150 °C | Clean, low sulphur |
| Forging finish | 900 °C minimum | Clean, low sulphur |
| Standard anneal | 850 to 1000 °C | H2 or cracked NH3 |
| Degas and decarburise | 838 to 1099 °C | Wet H2 |
| Oxide film growth | 650 to 700 °C | Air |
| Stress relief | approx. 550 to 650 °C | Protective |
10 / QualityTesting, inspection and certification
A FeNi29Co17 forging ships with a document package as well as the part itself. The scope below is what we quote against unless the specification asks for more.
| Test | Standard | When |
|---|---|---|
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 | Standard on rings and heavy sections. State the acceptance class |
| Chemical analysis | Spectrometric, per heat | Always |
| Tensile test | ASTM E8, ISO 6892-1 | Standard |
| Hardness | ASTM E10, ASTM E18 | Standard |
| Grain size | ASTM E112 | On request |
| Thermal expansion verification | ASTM E228 dilatometry | On request, recommended for sealing-critical work |
| Liquid penetrant | ASTM E165, EN 10228-2 | On request |
| Dimensional report | To drawing | Always |
| Mill certificate | EN 10204 3.1 | Standard |
| Third-party certificate | EN 10204 3.2 | On request. SGS, BV, TUV, LR or your own inspector |
Third-party witness inspection is welcome at our works. If your quality plan requires hold points, send it with the enquiry rather than after the order, since hold points affect the schedule and are better priced up front.
11 / ApplicationsWhere FeNi29Co17 forgings are used
| Sector | Typical forged components |
|---|---|
| Vacuum electronics | Power tube and microwave tube envelopes, travelling-wave and klystron ring sections, X-ray tube housings, cavity resonator bodies |
| Semiconductor packaging | Hybrid package frames, transistor and diode header blanks, integrated-circuit lead-frame stock, flat-pack and dual-in-line package bodies |
| Hermetic feedthroughs | Glass-to-metal and ceramic-to-metal feedthrough flanges, connector shells, high-voltage bushings |
| Aerospace and defence | Sensor housings, avionics enclosures, composite layup mould blanks, radar and microwave cavity parts |
| Scientific instruments | Dimensionally stable optical mounts, metrology frames, vacuum chamber transitions, spacers and seal rings |
| Thermostatic and control | Bimetal strip components, thermostat discs, temperature regulator parts, positioning devices |
| Lighting and lamps | Lamp bulb seal components, flash-bulb parts, high-power transmitting valve seals |
| Medical devices | Implantable device enclosures and feedthrough components requiring hermetic ceramic seals |
12 / FabricationMachining, welding and handling
Machining
FeNi29Co17 behaves like an austenitic stainless steel. It work-hardens and produces a long gummy chip. Use sharp positive-rake tooling, keep the cut underneath the previously hardened layer by running heavier feeds rather than lighter ones, run moderate surface speeds with generous coolant, and keep setups rigid. Dwelling in the cut produces the glazed hardened surface that then destroys the next tool.
On sealing parts, avoid sulphurised or chlorinated cutting oils on the surfaces that will be sealed, and do not machine FeNi29Co17 with tooling previously used on carbon steel. Both leave contamination that the wet-hydrogen anneal then has to remove, and it cannot always do so.
Welding
TIG, electron-beam and resistance welding all work. Use filler of matching composition, keep heat input low to limit grain growth, and anneal after welding if the part will be sealed. Until it is annealed out, the weld heat-affected zone has a different expansion history from the parent metal.
Handling and storage
Store clean, dry and away from carbon-steel swarf. Handle finished sealing surfaces with clean gloves, since fingerprints are a carbon source. Parts ship with the oxide film unformed unless we have been asked to oxidise them. The film is easily damaged in transit and is normally grown by the sealing house immediately before use.
13 / OrderingHow to get a firm quotation
FeNi29Co17 is quoted per drawing rather than per kilo off a price list. Forged weight, section thickness, machining allowance, anneal condition and test scope each move the price more than the alloy premium does.
Send these five items and we can return a firm price, usually within one working day
- Drawing or dimensions. A 2D drawing or 3D model is ideal. Failing that, give outside diameter, inside diameter, height or length and wall thickness, and state whether those are finished or rough dimensions.
- Governing specification. ASTM F15, DIN 17745, AMS 7727, GB/T 15018 4J29, or your own internal specification. If it is not fixed yet, say so and we will propose one.
- Delivery condition. As forged, rough machined or finish machined, plus the required heat-treatment condition.
- Test and certificate scope. Ultrasonic standard and acceptance class, mechanical tests, and whether you need EN 10204 3.1 or 3.2.
- Quantity and required date, plus the destination port so that freight can be included.
Jiangyin Jiangnan Metal Co., Ltd.
Open-Die Forging Works, Manufacturer
Jiangyin City, Jiangsu Province, China
14 / FAQFrequently asked questions about FeNi29Co17
What is FeNi29Co17?
FeNi29Co17 is a controlled-expansion iron-nickel-cobalt alloy containing nominally 29 % nickel, 17 % cobalt and the balance iron. Its mean coefficient of thermal expansion of roughly 5.3 x 10-6 /K between 25 °C and 450 °C closely matches borosilicate glass and alumina ceramic, so it is used to make hermetic glass-to-metal and ceramic-to-metal seals. FeNi29Co17 is the DIN 17745 designation for the alloy sold internationally as Kovar and specified in the United States as ASTM F15 / UNS K94610.
Is FeNi29Co17 the same as Kovar?
Yes. FeNi29Co17 is the European designation for the same Fe-29Ni-17Co controlled-expansion alloy marketed under the registered trade name Kovar. Equivalent designations are ASTM F15, UNS K94610, Werkstoff number 1.3981, DIN 17745 and SEW 385, AMS 7727 for bars and forgings, AFNOR NF A54-301, and Chinese grade 4J29 to GB/T 15018. Other trade names for the same alloy include Nilo K, Pernifer 2918, Rodar, Dilver P1, Vacon 12 and Nicosel.
What is the chemical composition of FeNi29Co17?
To DIN 17745 the limits are carbon 0.05 % max, silicon 0.30 % max, manganese 0.50 % max, cobalt 16.0 to 18.0 %, nickel 28.0 to 30.0 % and iron balance. ASTM F15 material is usually supplied to tighter limits, typically 0.02 % carbon max, 0.20 % silicon, 0.30 % manganese, 29.00 % nickel and 17.00 % cobalt, because narrow chemistry control keeps the thermal expansion curve inside the sealing window.
What is the thermal expansion coefficient of FeNi29Co17?
In the annealed condition the mean coefficient of thermal expansion measured from 25 °C is approximately 5.9 x 10-6 /K to 100 °C, 5.2 to 200 °C, 5.1 to 300 °C, 5.1 to 400 °C and 5.3 to 450 °C. Above the inflection point near 450 °C, which corresponds to the Curie temperature of about 435 °C, expansion rises steeply to roughly 7.8 x 10-6 /K at 600 °C. The flat region below 450 °C is the usable sealing range.
In which forged product forms is FeNi29Co17 available?
Jiangyin Jiangnan Metal Co., Ltd. supplies FeNi29Co17 as seamless rolled rings, open-die forged rings, forged flanges, discs and blanks, round bars, sleeves and bushings, tube sheets, shafts and spindles, and hollow forgings. All forms are made to customer drawing rather than from a fixed catalogue, with machining allowance agreed before forging.
What heat treatment does FeNi29Co17 need before glass sealing?
Degreased and machined parts are degassed and annealed in wet hydrogen or cracked ammonia between 838 °C and 1099 °C, roughly two hours at the lower temperature down to about 20 minutes at the upper, then cooled in the same atmosphere to below 299 °C. A thin, tightly adhering oxide film is then grown by heating in air at 650 to 700 °C until a dark grey to light brown film forms. That oxide is what the glass wets and bonds to.
Is FeNi29Co17 magnetic?
Yes. FeNi29Co17 is ferromagnetic at every temperature below its Curie point of about 435 °C, and paramagnetic above it. Permeability depends on heat treatment: the softer the annealed condition, the higher the permeability and the lower the hysteresis loss. If the design needs a non-magnetic controlled-expansion alloy, FeNi29Co17 is not a suitable choice.
Which testing and certification can be supplied with FeNi29Co17 forgings?
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 as specified on the order. Chemical analysis, tensile testing, hardness, grain size and dimensional inspection are standard. Certificates are issued to EN 10204 3.1 as a mill certificate, or EN 10204 3.2 counter-signed by a third-party body such as SGS, BV, TUV or Lloyd's Register.
Who manufactures FeNi29Co17 open-die forgings?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging works at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, manufacturing FeNi29Co17 forgings and seamless rolled rings to customer drawing. Enquiries: telephone +86 189 2135 9659, email sales@steelforgepieces.com.
How does FeNi29Co17 differ from Invar 36?
Invar 36 is an Fe-36Ni binary alloy with a much lower expansion coefficient of about 1.5 x 10-6 /K below 200 °C, chosen where near-zero dimensional change is the goal, such as metrology frames, LNG containment and precision structures. FeNi29Co17 has a higher expansion of about 5.3 x 10-6 /K, selected for its match to borosilicate glass and alumina. Specifying FeNi29Co17 for a low-expansion application, or Invar 36 for a glass seal, is the most common error between the two grades.
What is the maximum service temperature of FeNi29Co17?
For sealing duty the practical ceiling is about 450 °C, the inflection point above which the expansion curve leaves the borosilicate glass match and seal stresses rise quickly. The alloy itself melts near 1449 °C and is processed far above 450 °C, but a completed glass-to-metal seal should be designed to stay below the inflection point in service.
Can FeNi29Co17 be welded and machined?
FeNi29Co17 is readily welded by TIG, electron-beam and resistance methods. Matching filler is preferred and heat input should be kept low to limit grain growth. Machining behaves like an austenitic stainless steel, work-hardening and producing a gummy chip, so use sharp positive-rake tooling, rigid setups, moderate speeds and heavy feeds with generous coolant. Avoid carbon or sulphur pickup on parts destined for glass sealing, since surface contamination ruins the oxide film.
15 / SupplierAbout the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging works in Jiangyin, Jiangsu Province, China. We produce open-die forgings and seamless rolled rings to customer drawing in carbon steel, alloy steel, tool steel, stainless steel, nickel-base alloys and controlled-expansion alloys including FeNi29Co17, Invar 36, Invar 42, Alloy 46 and Alloy 52.
Jiangyin sits in the Yangtze River Delta forging cluster in southern Jiangsu, roughly two hours from Shanghai and its port. We are a manufacturer rather than a trading company. The forging, heat treatment and inspection described on this page take place at our own works, and customer and third-party inspectors are welcome on site.
Citing this page
This datasheet may be quoted or cited provided the source is attributed. Suggested citation:
Jiangyin Jiangnan Metal Co., Ltd. (2026). FeNi29Co17 Forgings (Kovar / ASTM F15 / 4J29), Technical Datasheet. Jiangyin, Jiangsu, China. https://www.steelforgepieces.com/Nickel-Alloy/FeNi29Co17.html
Technical queries about the data on this page: sales@steelforgepieces.com, +86 189 2135 9659
Sources for the property data on this page
- CarTech Kovar alloy technical datasheet, Carpenter Technology Corporation. Physical properties, mean coefficient of thermal expansion, sealing preparation practice.
- ASTM F15, Standard Specification for Iron-Nickel-Cobalt Sealing Alloy. Composition and product requirements.
- DIN 17745 and SEW 385. FeNi29Co17 composition limits.
- GB/T 15018. Chinese grade 4J29.
- AMS 7727 for bars and forgings, AMS 7726 for wire, AMS 7728 for sheet, strip and plate.
Property values on this page are typical published figures for the alloy, given for design guidance, and do not constitute a warranty. The certificate issued with your forging carries the values measured on your heat.
Page last reviewed 16 August , technical sales department, Jiangyin Jiangnan Metal Co., Ltd.