Alloy, tube 29NK

International Equivalent

Mark Analogue W. Nr. Aisi Uns En Order
29NK 1.3981 K94610 NiCo29-18 Delivery from the stock, in stock
29NK-t 1.3981 K94610 NiCo29-18 Delivery from the stock, in stock
29NK-m 1.3981 K94610 NiCo29-18 Delivery from the stock, in stock

Precision alloys are materials with specific mechanical properties. They have special physical and chemical characteristics, they are distinguished by extreme precision of their composition, absence of foreign impurities, thoroughness of production and processing. Most of them are created on the basis of iron, chromium, nickel, cobalt, copper, which gives the alloys those very special qualities that set them apart from the rest.


Kovar is a magnetic alloy of iron (54%), nickel (29%) and cobalt. The 17% Co in the composition greatly increases the value of the alloy. Kovar has a coefficient of linear expansion similar to glass and ceramic. Soldered into glass, it forms a reliable sealed joint used in electric vacuum and measuring equipment, construction of various sensors. This alloy has about half the electrical resistance of invar. Kovar is used to make capacitors with low TKE and variable capacitance. The disadvantage is considered to be its tendency to corrode in humid environments, which requires additional protective coating. Kovar capacitor plates are coated with a metal with good conductivity - most often, silver. The group of precision alloys stands out for their exclusive physical and chemical properties (magnetic, thermal, elastic, electrical), due to the accuracy of composition, thoroughness of manufacturing and processing and absence of unnecessary impurities.


Kovar is melted in arc furnaces using electroslag method. The alloying components are introduced into the composition in the form of ferroalloys. The chemical composition is strictly controlled during the production process, so Kovar belongs to the precision alloys. Ni in the alloy composition of 99.5% purity, gives the material high ductility. Due to its ductility, kovar can be rolled into the finest foil and yarn. The wire comes in two versions: tungsten carbide, rolled under cold pressure to increase elasticity, and soft, which is called annealed.

Percent composition

Co Ni Fe Mn С Si
17 29 up to 54 0.3 up to 0.01 0.2

The weight of a square meter of a forged product is between 0.5 and 18 kilograms. The coating must be clean and smooth. The surface is allowed to have minor damages: marks, dents from transportation, color variations. Color variations are also prescribed by the standard and depend on the conditions in which the product is stored. Also, a strip can be called a strip if it implies a section.

Physical properties of the alloy:

Description Designation
- Alloy data acquisition temperature [Grad] - T
- Modulus of elasticity of the 1st kind, [MPa] - E
- Coefficient of thermal linear expansion (at 20°C), [1/Grad] -a
- Specific electrical resistance [Ohm-m] -R -R
- Specific gravity [g/cm3] -r -r
- Heat transfer coefficient [W/(m-grad)] -l -l
- Specific heat capacity (at 20°C), [J/(kg-cold)] -C -C

Mechanical properties:

Description Designation
- Ultimate yield strength (yield strength for permanent deformation) [MPa] sT
- Tensile strength [MPa] sT
- Ratio constriction [ % ] y
- Tensile elongation [ % ] d5
- Brinell hardness, in [MPa] HB
- Impact toughness [ kJ/m2 ] KCU

Magnetic properties :

- Coercive force (within) [ A/m] Hc
- Magnetic permeability (not more than) [ MHN/m] Umax
- Losses (not more than) at frequency 50 Hz, and 1.0 Tl [ W/kg ] P1.0/50
- Magnetic induction Tl (not less) at magnetic field strength 100, in magnetic fields [ A/m] B100
- Coercive force (not more), [ A/m] Hc
- Magnetic permeability (not more than), [ MHN/m] Umax
- Losses per unit (max) at frequency 50 Hz and 1.0 Tl [ W/kg ] P1.0/50


Designation Description
Limited weldable - Must be preheated to 100-120°C with subsequent heat treatment
no restrictions - No need for preheating and final heat treatment
Difficult to weld - need for preheating to 200-300°C with final heat treatment


Various elements of radioelectronic devices. Kovar is characterized by minimal thermal expansion (between 20-400°C) and high thermal conductivity 19 W/m°C. It forms an airtight connection, which makes it indispensable for the production of vacuum tube devices. Kovar is in demand in power engineering and the nuclear industry. If necessary, welding wire 04Х20Н10Г2Б is used for automatic arc welding.


All 29NK grade products are certified. The technical documentation includes data on the chemical composition, the limiting percentage of impurities and mechanical properties of the products. From us you can buy in bulk a variety of semi-finished products for large-scale production. We also offer good conditions for retail buyers. You will be satisfied with the level of service and efficiency of service.

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Evek GmbH offers an unlimited range of high quality precision alloys at competitive prices. If you can't choose, our experienced managers are always available and ready to advise you. Order with us and you will receive certified products that meet international quality standards in the shortest possible time. If you value your time, contact our nearest office today or place your order online.