Kovar/Nilo K/Alloy K/UNS K94610/W. Nr. 1.3981

Kovar, also known as Nilo K or Alloy K, designated as UNS K94610 and W.Nr. 1.3981, is a nickel-iron-cobalt alloy specifically engineered to match the thermal expansion of borosilicate glass. Its excellent dimensional stability and low coefficient of thermal expansion make it ideal for glass-to-metal seals and electronic applications.

Kovar is commonly used in electronic components, hermetic seals, vacuum tubes, and semiconductor packaging. Its reliable performance in maintaining airtight seals and preventing thermal stress cracking makes it a preferred material in the aerospace, electronics, and telecommunications industries.

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Chemical Compositions
Physical Properties
Mechanical Properties
Standard Specifications
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Kovar/Nilo K/Alloy K/UNS K94610/W. Nr. 1.3981 Chemical Compositions

Iron (Fe)	nominal 53 %
Nickel (Ni)	nominal 29 %
Cobalt (Co)	nominal 17 %
Manganese (Mn)	0.50 % max.
Silicon (Si)	0.20 % max.
Carbon (C)	0.04 % max.
Aluminum (Al)	0.10 % max.
Magnesium (Mg)	0.10 % max.
Zirconium (Zr)	0.10 % max.
Titanium (Ti)	0.10 % max.
Copper (Cu)	0.20 % max.
Chromium (Cr)	0.20 % max.
Molybdenum (Mo)	0.20 % max.

Kovar/Nilo K/Alloy K/UNS K94610/W. Nr. 1.3981 Physical Properties

Density	lb/in3	0.295
	g/cm3	8.16
Melting point	°F	2640
	°C	1450
Inflection Point,	°F	840
	°C	450
Thermal Conductivity at 20°C (68°F)
	Btu•in/ft²•h•°F	116
	W/m•°C	16.7
Electrical Resistivity 20°C (68°F)
	ohm•circ mil/ft	259
	microhm-cm	43
Expansion coefficent (10ˉ⁶/℃)
	from 20°C to 100°C	6
	from 20°C to 150°C	5.8
	from 20°C to 200°C	5.5
	from 20°C to 250°C	5.3
	from 20°C to 300°C	5.1
	from 20°C to 350°C	4.9
	from 20°C to 400°C	4.9
	from 20°C to 450°C	5.3
	from 20°C to 550°C	6.2

Kovar/Nilo K/Alloy K/UNS K94610/W. Nr. 1.3981 Mechanical Properties

Temperature

Tensile Strength

Yield Strength
(0.2 % Offset)

Elongation

On 50mm

(2inch) %

Reduciton of

Area %

°C

°F

MPa

ksi

MPa

ksi

520

75.0

340

49.0

Kovar/Nilo K/Alloy K/UNS K94610/W. Nr. 1.3981 Standard Specifications

Rod, bar, sheet, strip, tubing, wire	Wire	Bars and forgings	Sheet, strip and plate
ASTM F 15	ASTM F 29, SAE AMS 7726	SAE AMS 7727	SAEAMS 7728

Standard product forms of Kovar/Nilo K/Alloy K/UNS K94610/W. Nr. 1.3981 are pipe, tube, sheet, strip, plate, round bar, flat bar, forging stock, hexagon and wire. The products are available in a wide variety of sizes. Please contact us at [email protected] for full information.