4J29 (Kovar, UNS K94610) is an iron-nickel-cobalt controlled-expansion sealing alloy. With a CTE of about 4.6–5.2×10⁻⁶/°C from 20 to 450 °C it matches borosilicate glass and alumina ceramic, making it the standard for vacuum tubes, semiconductor packaging and hermetic seals.
As a manufacturer and global exporter of special alloys since 2012, Shanghai Hangbo Alloy Group Co., Ltd. supplies Kovar / 4J29 as round bars (φ2–600 mm, up to 12 m), plates & sheets (0.5–100 mm thick, up to 2500 mm wide), precision strip (0.02–3.0 mm, ±0.005 mm tolerance), seamless tubes & pipes (φ6–630 mm OD, 0.5–40 mm wall) — all with EN 10204 3.1 certified material test reports.
Kovar / 4J29 Chemical Composition (wt%)
| Element | Content (wt%) | Element | Content (wt%) |
|---|---|---|---|
| Fe (铁) | Balance | Si (硅) | ≤ 0.30 |
| Ni (镍) | 28.5–29.5 | C (碳) | ≤ 0.03 |
| Co (钴) | 16.8–17.8 | P (磷) | ≤ 0.020 |
| Mn (锰) | ≤ 0.50 | S (硫) | ≤ 0.020 |
Kovar / 4J29 Mechanical Properties
| Property | Value |
|---|---|
| Tensile strength (Rm) | ≥ 520 MPa |
| Yield strength (Rp0.2) | ≥ 340 MPa |
| Elongation (A) | ≥ 25 % |
| Hardness | ≤ 190 HB |
| Density | 8.36 g/cm³ |
| Melting range | 1450–1470 °C |
| Thermal conductivity | 17.0 W/m·K |
| Young's modulus | 138 GPa |
| Max service temperature | −80 ~ +450 ℃ |
Key Advantages
- CTE precisely matched to borosilicate glass and alumina ceramic
- Highly reliable hermetic seals with long thermal-cycle life
- Good machinability plus plating and welding performance
- Forms a strong chemical bond with glass
Relevant Standards
- ASTM F15
- GB/T 14985
- UNS K94610
Typical Applications
- IC and power device packages
- Vacuum tubes, magnetrons and travelling-wave tubes
- Aerospace and military hermetic electronic packaging
- Sensor and relay housings
- Solar cell and laser device packaging
Why Buy from Hangbo Alloy?
- Factory-direct manufacturer — founded 2012, headquartered in Shanghai Qingpu
- Full product range — bar, plate, sheet, strip, tube, forging, welding wire, flanges and machined parts
- Certified quality — ISO 9001:2015, GB/T 19001-2016, GJB 9001C-2017, EN 10204 3.1 mill test certificates with third-party inspection (SGS / BV / TUV) available on request
- Complete mill documentation — chemical analysis, mechanical test, ultrasonic test (UT), hardness and grain-size reports with every shipment
Contact Us — Shanghai Hangbo Alloy Group Co., Ltd.
Shanghai Hangbo Alloy Group Co., Ltd.
📍 No. 388 Songhuang Road, Qingpu District, Shanghai, China
📞 Tel / WhatsApp: +86 15618279078
✉️ Email: demi@nickel-alloy.com
🕒 Available 24 hours a day, 7 days a week — enquiries answered around the clock.
Send your drawing or enquiry (grade, form, size, quantity, standard) for a same-day quotation.
Frequently asked questions
What is the difference between 4J29 and 4J36?
4J36 (Invar) targets minimal expansion (about 1.2×10⁻⁶/°C) for dimensionally stable parts, while 4J29 (Kovar) targets a controlled expansion (about 5×10⁻⁶/°C) matched to glass and ceramic for hermetic sealing. 4J29 contains 17% cobalt and costs more; the two are not interchangeable.
What forms and sizes are available?
We supply Kovar / 4J29 as round bars (φ2–600 mm, up to 12 m), plates & sheets (0.5–100 mm thick, up to 2500 mm wide), precision strip (0.02–3.0 mm, ±0.005 mm tolerance), seamless tubes & pipes (φ6–630 mm OD, 0.5–40 mm wall). Custom lengths, tolerances and machining to drawing are available on request.
What is the MOQ and lead time?
MOQ is flexible — trial orders from a single piece are welcome. Stock sizes ship in 3–7 days; custom forgings and machined parts typically 15–35 days depending on quantity and process.
Can you provide third-party inspection and shipping to my port?
Yes. SGS / BV / TUV or your nominated inspector can witness all tests before shipment. Full export documentation is provided, and we ship worldwide by sea or air on FOB, CIF or DDP terms.