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Hot Forged Controlled Expansion Kovar Alloy , Round Bar Glass Sealing Alloy

Place of Origin China
Brand Name XUNSHI
Certification ISO9001:2015
Model Number Kovar
Minimum Order Quantity 20kg
Price Negotiable
Packaging Details Wooden case
Delivery Time 3-5 weeks
Payment Terms T/T
Supply Ability 1000kg per week

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Product Details
Material Fe-Ni-Co Forms Strip, Bar, Wire, Pipe
Equal Grades 4J29(China), ASTM F-15, NILO K, Pernifer 2918, Rodar, Dilvar P1, UNS K94610, 29-17 Alloy Size Range 20~300mm
Density 8.36g/cm3 Tc 430°C
High Light

iron nickel alloy


corrosion resistant alloys

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Product Description

Kovar Controlled Expansion Alloy Hot Forged Round Bar for Glass Sealing Application



A-ONE ALLOY keeps in stock Kovar hot fogerd round bar from diameter 20mm to diameter 300mm. And we could make fast delivery for customized sizes as well as forged pieces.



Kovar controlled expansion alloy, most likely know as 4J29 in China, is a Nickel Iron alloy with 29% Nickel, 17% Cobalt and the remaining balance is Iron.


Kovar controlled expansion alloy, was invented to meet the need for a reliable glass-to-metal seal, which is required in electronic devices such as light bulbs, vacuum tubes, cathode ray tubes, and in vacuum systems in chemistry and other scientific research area.


Kovar has thermal expansion similar to glass. Meanwhile its nonlinear thermal expansion curve can often be made to match a glass. This makes it the most popular controlled expansion alloy so far.


Chemical compostion of Kovar

Alloy % Ni Cr Co Cu C Mn Si P S Mo Fe
Kovar Min 28.5   16.8               Rem
Max 29.5 0.2 17.8 0.20 0.03 0.50 0.30 0.02 0.02 0.20


The average linear expansion coefficient(10-6C)

20~100°C 20~300°C 20~400°C 20~450°C 20~500°C 20~530°C 20~600°C
4.6~5.2 5.1~5.5


Applications of Kovar

  •  Light bulbs
  •  Vacuum tubes
  •  Cathode ray tubes
  •  Power tubes
  •  Microwave tubes
  •  Transistoers
  •  Diodes
  •  Hybrid packages
  •  Other kinds of scientific instruments

Forms available at A-ONE ALLOY

  •  Bar
  •  Tube
  •  Strip
  •  Wire
  •  Plate
  •  Capillary