ASTM F15 / UNS K94610 Kovar Alloy Sheet | Custom Sizes, Reliable Manufacturer, Fast Delivery

ASTM F15 / UNS K94610 Kovar Alloy Shee is the iron-nickel-cobalt controlled-expansion alloy you choose when you need a hermetic glass-to-metal or ceramic-to-metal seal that survives thermal cycling without cracking. If your application requires precise thermal expansion matching to borosilicate glass or alumina ceramic - transistor headers, IC lead frames, vacuum tube components, or optoelectronic packages - Kovar sheet is the answer.

Kovar alloy sheet (UNS K94610, ASTM F15, Chinese grade 4J29) is a nickel-iron-cobalt alloy containing nominally 29% nickel, 17% cobalt, and 53% iron. Its coefficient of thermal expansion is engineered to match borosilicate glasses and alumina ceramics across a wide temperature range, making it the standard material for glass-to-metal seals in electronic applications.

As a reliable manufacturer of Kovar alloy sheet, we supply custom sizes with fast delivery and full traceability. Every shipment includes a Mill Test Certificate documenting chemical composition and mechanical properties to ASTM F15.

Chemical Composition

Typical Mechanical Properties

Kovar sheet and strip are available in a wide range of thicknesses for different applications.

The material is typically supplied in the annealed (soft) condition and can be finished as bright annealed (clean and shiny) or pickled (chemically cleaned)

• Seal cracking & vacuum leakage: Matched thermal expansion with borosilicate glass and alumina ceramic prevents crack‑induced air leakage during heating‑cooling cycles, securing long‑term hermetic performance.
• Low‑temperature structural failure: Phase‑stable alloy matrix without martensite transformation at ultra‑low temperature, keeps mechanical integrity for cryogenic electronic equipment.
• Poor batch repeatability: Vacuum‑melting production with strict ASTM F15 compliance, consistent chemical composition and CTE across batches; avoids sealing failure caused by material deviation.
• Dimensional tolerance errors for precision stamping: Uniform grain structure enables precise cutting and stamping, minimises post‑processing scrap for miniature packaging parts.
• Long procurement lead‑time pain: Standard sizes kept in stock for fast delivery; custom‑size processing service shortens project lead‑time for prototype and mass orders.
• Traceability risk: Each shipment comes with MTC mill test report including chemical analysis, mechanical and expansion test data to pass incoming quality inspection.

1. Custom sizes cut to your drawing. Thickness, width, and length per your specification. No wasted material.

2. Full ASTM F15 / UNS K94610 compliance. Mill Test Certificate with every shipment.

3. Ready to ship from stock. Standard sizes ship in 7–15 days. Custom-cut confirmed at order review.

4. Technical support for sealing applications. Our team can advise on pre-oxidation treatment, sealing parameters, and heat treatment cycles.

5. Competitive pricing from China. Direct factory supply with flexible MOQ.

6. Full traceability. Every batch traceable from raw material to finished sheet.

Kovar UNS K94610 is selected when metal must form vacuum‑tight joints with glass or ceramic under temperature cycling. Ordinary carbon steel or stainless steel cannot replace it for hermetic sealing due to mismatched thermal expansion coefficient.

Main application fields:

• Glass‑to‑metal hermetic sealing: vacuum tube components, feed‑through pins, bulb sealing parts
• Semiconductor & electronic packaging: chip base plates, housing headers, lead frame blanks
• Sensor and optical instruments: sealing substrates for precision sensors
• Aerospace & defence electronics: high‑low temperature resistant sealed electronic assemblies
• Microwave and communication devices: ceramic‑metal sealed structural partsSpecial Me...

Selection Tip: Pick ASTM F15 Kovar sheet if your design requires zero‑leak hermetic seal over repeated thermal cycles. If hermetic glass sealing is not required, Invar 36 or 4J42 may be considered as alternative options for cost optimisation.

Besides ASTM F15 Kovar alloy sheet stock, custom‑size ASTM F15 Kovar alloy Bar and  is frequently adopted for manufacturing seal lids and package housing blanks for semiconductor hermetic packages.

Batch‑to‑batch consistency of thermal expansion coefficient (CTE) is the top priority for hermetic sealing projects. Even minor CTE deviation between different heat‑lots will introduce residual thermal stress, which further triggers glass‑ceramic seal cracking, micro‑leakage and final device failure.

When placing RFQ for custom‑size Kovar alloy sheet, you must explicitly require per‑batch CTE test data together with complete EN10204 3.1 MTC documentation, rather than only relying on generic datasheet values.Review our full technical article to avoid typical sourcing mistakes that cause glass‑ceramic seal cracking and package leakage.

Besides CTE and certification, you should also clarify critical items in your inquiry:

• Confirm governing standard: ASTM F15 / UNS K94610 for North‑American & European semiconductor projects
• Define temper: soft‑annealed for stamping / deep‑drawing; cold‑rolled hard for structural support
• Specify dimensional tolerance and surface finish, especially plating‑ready surface for subsequent nickel‑gold plating
• Require full heat‑lot traceability for aerospace and high‑reliability semiconductor applications

At HSMetal, each lot of our Kovar alloy sheet is inspected with measured CTE results and supplied with traceable EN10204 3.1 MTC, helping you eliminate sealing risks caused by unstable material performance.

HSMetal is a professional ASTM F15 / UNS K94610 Kovar Alloy Sheet manufacturer and exporter in China, focusing on high-precision controlled expansion alloys for semiconductor packaging, aerospace hermetic sealing, and electronic precision component industries.

With years of in-depth experience in special alloy production and customization, we specialize in manufacturing standard and custom-size Kovar alloy sheet, strictly following ASTM F15 industrial specifications. We fully understand the core differences between Kovar alloy and Invar alloy, alternative equivalent grades, and high-temperature alloy application boundaries, enabling us to provide accurate material selection analysis, cost optimization solutions, and risk avoidance guidance for global buyers.

We implement a strict full-process quality control system. Every batch of our 4J29 Kovar sheet is equipped with complete Mill Test Certificate (MTC), covering chemical composition, thermal expansion coefficient (CTE), and mechanical property data, ensuring stable and consistent sealing performance for long-cycle temperature-variable working environments.

Different from ordinary trading companies, we support one-stop services including precision cutting, custom sizing, surface finishing, and batch customized production. With stable monthly output, ready-to-ship stock, and flexible MOQ, we effectively solve customers' pain points of unstable quality, unclear material selection, uncontrollable cost, and delayed delivery.

Adhering to technical professionalism and transparent quality standards, we have built long-term cooperative relationships with precision manufacturing enterprises from Europe, America, Southeast Asia and other regions, becoming a reliable and trustworthy Kovar alloy sheet supplier for global industrial projects.

Our Factory

 

Metal Strip Continuous Annealing Production Line

Hot Rolling Mill For High Performance Alloy Plate Production Equipment

1.5T Protective Atmosphere Electroslag Remelting Furnace

Rotating+Passing Eddy Current Flaw Detector

Electron Microscope

German Spike Spectral Analyzer

Q1: What is the core difference between Kovar alloy and Invar alloy?

A: Kovar (4J29) contains cobalt and its thermal expansion matches hard borosilicate glass for hermetic sealing. Invar 36 (4J36) is nickel-iron alloy without cobalt, for ultra-stable dimension in precision measuring and optical parts. Invar cannot replace Kovar for glass-to-metal sealing, otherwise the seal will crack after thermal cycling.

Q2: What is ASTM F15 / UNS K94610 Kovar alloy sheet used for?

A: Kovar alloy sheet (UNS K94610, ASTM F15) is used for glass-to-metal seals in electronic applications, including transistor leads and headers, integrated-circuit lead frames, hybrid circuit casings, power tubes, microwave tubes, and optoelectronic component packages.

Q3: What is the chemical composition of Kovar?

A: Kovar contains nominally 29% nickel, 17% cobalt, and 53% iron. The full composition per ASTM F15 is Ni 28.0–30.0%, Co 16.8–17.8%, Fe balance, with Mn ≤0.50%, Si ≤0.30%, C ≤0.04%.

Q4: What is the thermal expansion coefficient of Kovar?

A: Kovar's CTE is approximately 4.9 × 10⁻⁶/°C (30–400°C) or 5.1–5.5 × 10⁻⁶/°C (20–400°C), depending on the measurement range. This matches borosilicate glass and alumina ceramic.

Q5: Can Kovar sheet be deep drawn?

A: Yes. Kovar can be formed and deep drawn from the annealed temper. A 1/8 hard temper is optimum for heavy piercing.

Q6: Can Kovar sheet be welded?

A: Yes. Kovar can be joined to other metals by welding, brazing, and soldering. The joint design must account for Kovar's lower expansion coefficient compared to most other metals.

Q7: What is the maximum service temperature of Kovar?

A: Kovar's Curie temperature is approximately 435°C. The alloy is typically used in the −60°C to +450°C range for glass-to-metal sealing applications.

Q8: What is the Chinese equivalent of Kovar?

A: The Chinese equivalent is 4J29. The German equivalent is W.Nr 1.3981. These are direct equivalents.

Q9: Can you provide a sample before I place a production order?
A:Yes. We supply test samples for qualification. Sample cost is credited against your first production order.

Q10: What is the one-line rule for choosing Kovar sheet?

A: Choose ASTM F15 / UNS K94610 Kovar alloy sheet when you need a hermetic glass-to-metal or ceramic-to-metal seal that survives thermal cycling - Kovar's CTE matches borosilicate glass and alumina ceramic, minimizing sealing stress and preventing cracking.

Q11: What surface options are available for Kovar sheet?

A: Mill finish, pickled finish and bright polished surface are available. Special surface treatment such as plating can be arranged per customer requirements.

Q12: Can you match a specific thermal expansion curve?
A:Send us your target CTE range and reference temperature interval. We will confirm whether standard 4J29 meets your requirement or whether a custom composition is needed.

Q13: Can you deliver fast for urgent projects?

A: Conventional dimension Kovar sheets are kept in stock, supporting fast delivery. For non‑standard custom dimensions we provide confirmed lead‑time before order placement.

Q14: Do you supply Kovar in forms other than sheet?

A:We also supply Kovar rod, wire, strip, and tube. If you need a machined or formed component, we can discuss secondary processing.

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