01 / GradeWhat is GLASS SEAL 46?
GLASS SEAL 46 belongs to the family of iron-nickel controlled-expansion alloys covered by ASTM F30, Standard Specification for Iron-Nickel Sealing Alloys. Nickel content sets the coefficient of thermal expansion. At a nominal 46 %, the alloy sits close to the expansion of soft lead glass and soda-lime glass, and when metal and glass expand and contract together the seal survives thermal cycling without cracking.
The alloy is mildly magnetic at room temperature and has a Curie point in the region of 460 °C. During wet-hydrogen annealing it takes a dense adherent oxide. That oxide layer is what the molten glass wets and bonds to.
Names you may see for the same material
Purchasing specifications, mill certificates and drawings use several names for this grade. They all refer to the same iron / 46 % nickel sealing alloy:
| Designation | Origin or system |
|---|---|
| GLASS SEAL 46 | Common trade description for the glass-sealing grade |
| Alloy 46 / Ni 46 | Generic industry designation |
| ASTM F30 Type 46 | ASTM International specification |
| UNS K94600 | Unified Numbering System (USA) |
| Nilo 46 | Special Metals trade name |
| Pernifer 46 | VDM Metals trade name |
| NiFe 47 / W.-Nr. 1.3926 | Nearest DIN or EN equivalent. Confirm against your specification |
Trade names are the property of their respective owners and are quoted for cross-reference only. Jiangyin Jiangnan Metal Co., Ltd. supplies to ASTM F30 or to the customer's own specification.
02 / ChemistryChemical composition of GLASS SEAL 46
Per ASTM F30, Type 46. Weight %
| Element | Composition, wt % |
|---|---|
| Nickel (Ni) | 46.0 nominal |
| Cobalt (Co) | 0.50 max. |
| Chromium (Cr) | 0.25 max. |
| Carbon (C) | 0.05 max. |
| Manganese (Mn) | 0.80 max. |
| Silicon (Si) | 0.30 max. |
| Aluminium (Al) | 0.10 max. |
| Phosphorus (P) | 0.025 max. |
| Sulfur (S) | 0.025 max. |
| Iron (Fe) | Balance |
Carbon, sulfur and silicon are held low deliberately. Residuals gas out during the glass-sealing cycle and produce bubbles at the interface. Every heat we forge is supplied with its own ladle analysis on the EN 10204 certificate.
03 / MechanicalMechanical properties of GLASS SEAL 46
Typical values, annealed condition, room temperature
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 552 MPa | 80 ksi |
| Yield strength (0.2 % offset) | 242 MPa | 35 ksi |
| Elongation | 30 % (50 mm) | 30 % in 2 in. |
Physical and thermal properties
| Property | Typical value |
|---|---|
| Density | approx. 8.1 g/cm³ (0.293 lb/in³) |
| Mean coefficient of thermal expansion, 30-400 °C | approx. 7.5-8.5 × 10-6 /°C |
| Curie temperature | approx. 460 °C |
| Melting range | approx. 1,450 °C |
| Modulus of elasticity | approx. 145 GPa (21 × 106 psi) |
| Electrical resistivity | approx. 0.45 µΩ·m |
| Thermal conductivity | approx. 14 W/m·K |
These physical values are indicative and given for design guidance only. Thermal expansion in particular depends on melt chemistry, section size and heat-treatment history. ASTM F30 and the agreed order specification govern acceptance. The tested values appear on the mill certificate issued with your forgings.
04 / SelectionGLASS SEAL 46 compared with Alloy 42, 48, 52 and Kovar
Choosing between the sealing alloys is almost entirely a question of matching thermal expansion to the glass or ceramic being sealed. The table below is the shortlist engineers work from.
| Alloy | Nominal composition | Mean CTE, 30-400 °C (× 10-6 /°C) |
Typically sealed to |
|---|---|---|---|
| Alloy 42 | Fe / 42 % Ni | approx. 4.3-5.0 | Hard glass, ceramic, semiconductor lead frames |
| Kovar (ASTM F15) | Fe / 29 % Ni / 17 % Co | approx. 5.1-5.9 | Borosilicate glass (Corning 7052/7056), alumina |
| GLASS SEAL 46 | Fe / 46 % Ni | approx. 7.5-8.5 | Soft lead glass and soda-lime glass |
| Alloy 48 | Fe / 48 % Ni | approx. 8.5-9.2 | Soda-lime glass, higher-expansion soft glass |
| Alloy 52 | Fe / 51 % Ni | approx. 9.7-10.3 | Soft lead glass, lamp and eyelet seals |
| Invar 36 | Fe / 36 % Ni | approx. 1.2-2.0 | Not a sealing alloy. Dimensional stability, LNG, tooling |
Expansion figures are typical published ranges for annealed material and vary between producers and heat-treatment routes. Verify against ASTM F30 and your glass supplier's expansion data before finalising a design.
Where the seal partner is soft lead or soda-lime glass, GLASS SEAL 46 is the usual first choice, while borosilicate calls for Kovar instead. Alloy 48 and Alloy 52 are the next steps up if a slightly higher expansion is wanted.
05 / Product formsGLASS SEAL 46 forged forms we produce
Everything below is made by open-die forging or ring rolling to the customer's drawing. There is no catalogue and no fixed tooling cost.
Forged rings and seamless rolled rings
Rolled on 3 m and 6 m ring mills, plain or contoured section.
Forged flanges
Blind, weld-neck, slip-on and special profiles, rough or finish machined.
Forged round, square and flat bars
Straight lengths to 12,000 mm, sawn to your cut list.
Forged discs, disks and blocks
Solid or trepanned, with radial or axial grain flow as specified.
Forged shafts and spindles
Plain, stepped and eccentric shafts, straightened and stress relieved.
Forged sleeves and bushings
Hollow forgings, bored and turned to your ID and OD tolerance.
Forged tubes and pipes
Thick-wall hollow forgings for hermetic housings and feed-throughs.
Forged tube sheets
Drilled or blank, in single pieces up to 6,000 mm diameter.
Size and weight envelope
| Parameter | Range |
|---|---|
| Outside diameter | 100 mm to 6,000 mm |
| Length | 100 mm to 12,000 mm |
| Piece weight | 10 kg to 15,000 kg |
| Forging hammers | 1 t, 3 t, 6 t, 9 t |
| Hydraulic press | 4,500 t |
| Ring rolling mills | 3 m and 6 m |
06 / RouteHow we melt, forge and heat treat GLASS SEAL 46
Glass-sealing alloys are unforgiving about cleanliness. Gas and inclusions that would be cosmetic in a structural steel become bubbles and leak paths at a glass-to-metal interface, so the melting route matters as much as the forging.
1. Melting
GLASS SEAL 46 is melted by EAF + VOD followed by ESR (electro-slag remelting). VOD strips carbon and dissolved gas; ESR refines the solidification structure and cuts non-metallic inclusions. Where a customer specification calls for it, we also supply VIM + ESR or VIM + VAR material.
2. Forging
Ingots are soaked and forged in the range of roughly 1,180 °C down to about 900 °C, with re-heats as needed to keep the finishing temperature under control. Reductions are planned so the grain flow follows the part contour: circumferential in rolled rings, axial in shafts.
3. Heat treatment
Forgings are annealed to restore ductility and stabilise expansion behaviour. For parts going on to be glass sealed, a wet-hydrogen anneal in the region of 900-1,050 °C is the usual practice. It decarburises the surface and develops the adherent oxide the glass needs to wet. Stress-relief, normalising, and quench-and-temper cycles are available where the drawing calls for them.
4. Machining
We deliver as-forged, rough machined with agreed stock allowance, or fully finish machined to your drawing.
“We do not hold GLASS SEAL 46 as a stock item. Every piece is forged against a drawing or a dimension list, with the melting route, forging reduction and anneal chosen for what the part has to do. That is why we ask for the seal design, not just the size.”
07 / QualityTesting, inspection and certification
- Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, to the acceptance class stated on your order.
- Chemical analysis, ladle and, on request, product analysis against ASTM F30 limits.
- Mechanical testing, tensile, hardness and, where specified, impact testing from prolongations or sacrificial rings.
- Thermal expansion testing by dilatometry where the order specifies a CTE band rather than composition alone.
- Dimensional inspection reports against the released drawing.
- Certification to EN 10204 3.1, or 3.2 with third-party witness (TÜV, SGS, BV, Lloyd's and equivalent).
Tell us the acceptance standard at enquiry stage. Ultrasonic class and CTE tolerance change the forging reduction and the ingot size we start from, so they affect price and lead time more than the finished dimensions do.
08 / ApplicationsWhere GLASS SEAL 46 forgings are used
Because its expansion tracks soft glass so closely, Alloy 46 turns up wherever a metal part has to be fused to glass and stay hermetic:
- Glass-to-metal seals for electron tubes, hermetic feed-throughs and vacuum devices, usually as forged rings and shafts.
- Lamp and lighting components, lead-ins and mounts sealed into soda-lime and lead glass.
- Microelectronic packaging, housings, headers, covers and specialised frames for hermetic devices.
- Telecommunications hardware, echo boxes, cavity resonators and filters for microwave and mobile equipment.
- Bimetal and thermostatic strip, as the high-expansion side of a thermostatic bimetal.
- Instrumentation, magnetic shielding, small transformer cores, metrology and positioning devices.
- Precision assemblies, seals, spacers, condenser blades and optical-device frames where dimensional stability matters.
09 / OrderingHow to order GLASS SEAL 46 forgings
- Send the drawing or the dimensions. A PDF, STEP or DWG file to sales@steelforgepieces.com, or simply OD × ID × height for a ring, or diameter × length for a bar.
- State the specification. ASTM F30 Type 46, or your own drawing spec. Include the UT class, certificate type (EN 10204 3.1 or 3.2) and delivery condition.
- Receive the quotation. We reply with price, forged weight, delivery condition and lead time. Quotations are normally back with you within one working day.
- Approve and produce. Ingot is allocated, forged, heat treated, machined, tested and certified. Documentation travels with the shipment.
Enquiries in English or Chinese are equally welcome: +86 189 2135 9659.
10 / FAQFrequently asked questions about GLASS SEAL 46
What is GLASS SEAL 46 made of?
GLASS SEAL 46 is an iron-nickel alloy with a nominal 46 % nickel and the balance iron. Cobalt is limited to 0.50 % max., chromium to 0.25 %, manganese to 0.80 %, silicon to 0.30 %, aluminium to 0.10 %, carbon to 0.05 %, and phosphorus and sulfur to 0.025 % each, per ASTM F30.
Which standard covers GLASS SEAL 46?
ASTM F30, Standard Specification for Iron-Nickel Sealing Alloys, Type 46. The same material carries the UNS number K94600. Jiangyin Jiangnan Metal Co., Ltd. supplies GLASS SEAL 46 forgings to ASTM F30 or to a customer's own written specification.
Is GLASS SEAL 46 the same as Alloy 46, Nilo 46 and UNS K94600?
Yes, these are different names for the same iron / 46 % nickel sealing alloy. Alloy 46 is the generic designation, Nilo 46 and Pernifer 46 are producers' trade names, UNS K94600 is the US numbering-system code, and ASTM F30 Type 46 is the specification. The nearest DIN or EN equivalent is usually quoted as NiFe 47 (W.-Nr. 1.3926), which should be confirmed against your own specification.
What kind of glass does Alloy 46 seal to?
Soft lead glass and soda-lime glass. Its mean thermal expansion of roughly 7.5 to 8.5 × 10-6 /°C over 30-400 °C is close enough to those glasses that the seal survives repeated thermal cycling. For borosilicate glass you would use Kovar (ASTM F15) instead, and for higher-expansion glasses, Alloy 48 or Alloy 52.
What is the difference between Alloy 42, 46, 48 and 52?
Nickel content, and therefore thermal expansion. Alloy 42 (Fe / 42 % Ni) expands at about 4.3 to 5.0 × 10-6 /°C and suits hard glass and lead frames. GLASS SEAL 46 sits at about 7.5 to 8.5 and suits soft lead and soda-lime glass. Alloy 48 sits at about 8.5 to 9.2, and Alloy 52 (Fe / 51 % Ni) at about 9.7 to 10.3 for soft lead glass and lamp seals. You pick the alloy whose expansion curve most closely follows the glass you are sealing.
What sizes of GLASS SEAL 46 forgings can you supply?
Jiangyin Jiangnan Metal Co., Ltd. forges GLASS SEAL 46 from 100 mm to 6,000 mm diameter, up to 12,000 mm long, at piece weights from 10 kg to 15,000 kg. The works runs 1, 3, 6 and 9 tonne forging hammers, a 4,500-tonne hydraulic press, and 3 m and 6 m seamless ring rolling mills.
How is GLASS SEAL 46 melted?
By EAF + VOD followed by ESR (electro-slag remelting) as standard. VOD removes carbon and dissolved gas, and ESR refines the structure and reduces inclusions. Both matter for glass sealing, because residual gas produces bubbles at the seal interface. VIM + ESR or VIM + VAR routes are available where a specification requires them.
Can GLASS SEAL 46 forgings be machined to a finished drawing?
Yes. We supply as-forged, rough machined with an agreed stock allowance, or fully finish machined to the customer's drawing, including bored and turned sleeves, drilled tube sheets and profiled rings.
What testing and certificates are supplied?
Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, chemical analysis against ASTM F30, tensile, hardness and impact testing as specified, dilatometry where a CTE band is required, and dimensional reports. Certification is issued to EN 10204 3.1, or 3.2 with third-party witness such as TÜV, SGS, BV or Lloyd's.
Is there a minimum order quantity for GLASS SEAL 46?
There is no catalogue minimum. Every GLASS SEAL 46 forging is made to order, so single prototype pieces and repair parts are quoted alongside series quantities. Price and lead time are set against the drawing, the specification and the ingot size the part needs.
How do I get a price for GLASS SEAL 46 forgings?
Email the drawing or dimensions to sales@steelforgepieces.com, or call +86 189 2135 9659. Jiangyin Jiangnan Metal Co., Ltd. is located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, and quotes worldwide.
11 / ManufacturerAbout Jiangyin Jiangnan Metal Co., Ltd.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, about ninety minutes from Shanghai. We forge carbon steel, alloy steel, tool steel, stainless steel and nickel alloys into rings, flanges, bars, shafts, discs, sleeves and tube sheets, and we roll seamless rings up to 6 m diameter.
The works serves the oil and gas, power generation, chemical processing, valve, pressure-vessel and electronics industries, and exports under EN 10204 3.1 and 3.2 certification.
| Company | Jiangyin Jiangnan Metal Co., Ltd. |
|---|---|
| Business | Open-die forging factory and seamless rolled ring manufacturer |
| Address | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone | +86 189 2135 9659 (0086-189-2135-9659) |
| sales@steelforgepieces.com | |
| Website | www.steelforgepieces.com |
| Certification | EN 10204 3.1 / 3.2, third-party witness available |
Cite this datasheet
Jiangyin Jiangnan Metal Co., Ltd. (2026). "GLASS SEAL 46 forged rings, flanges, bars and discs. ASTM F30 Alloy 46 / UNS K94600." Open-die forging works, No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Retrieved from https://www.steelforgepieces.com/Nickel-Alloy/GLASS-SEAL-46.html