Invar 36, Invar 42, Kovar, ASTM-B-753, ASTM-F-1684, MIL-I-23011

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Please call 800-707-6061 or fax RFQs to 800-707-3439.  We will get back to you ASAP. Thanks.


* All Trademarks and/or Trade names are the properties of their respective owners.


About Invar

Invar, also known as Invar 36, is a nickel steel alloy with unique low rates of thermal expansion.


1) Invar 36

* Invar 36 Sheet, Plate Per Chem Mil-I-23011C CL 7, Boeing D-33028, ASTM-B-753, F-1684

  Thickness: 0.015"~6.000" , Width: 10"~72", Length: 60"~144"

* Invar 36 Bar Per Mil-I-23011 CL 7, ASTM-B-752 Chem Only, Chem Mil-S-16598B, ASTM-F1684

  Diameter: 0.078"~6.000", Length: 144" Random Length


2) Invar 42

* Invar 42 Plate Per Chem Mil-I-23011 CL 5, Chem ASTM-F-30, Chem ASTM-B-753

  Thickness: 0.250"~4.000", Width: 18"~48", Length: 12"~144"


About Kovar

Kovar alloy is a vacuum melted, iron-nickel-cobalt, low expansion alloy whose chemical composition is controlled within narrow limits to assure precise uniform thermal expansion properties.

3) Kovar

* Kovar Sheet, Plate Per Mil-I-23011 CL 1, ASTM-F-15, Thickness: 0.005"~1.000", Width: 12"~48", Length: 36"~120"

* Kovar Bar Per ASTM-F-15, Diameter: 0.500"~0.500", Length: 144" Random Length


Invar 36 Specifications: UNS K93600, UNS K93603

Chemical Composition, %

  Ni Fe Mo C Cu Mn Si P S Cr
MIN 35.0 - - - - - - - - -
MAX 37.0 Balance 0.5 0.1 0.5 0.6 0.35 0.025 0.025 0.5


  • Low expansion rate up to 500 Degrees F
  • Readily weldable


  • Tooling and dies for composite forming
  • Cryogenic components
  • Laser components

Physical Properties

Density: 0.293 lb/in3
Melting Point: 2605 Degrees
Electrical Conductivity: 69.3 Btu • ft/ ft² • hr •  Degrees F

Temperature,  Degrees F -328 -148 212 302 392 482 572 662 752 842 932
Modulus of Elasticity, Dynamic psi x 106 0.8 0.7 0.8 1.1 1.4 1.9 3.1 4.0 4.7 5.2 5.6


* 70 Degrees F to indicated temperature.

Mechanical Properties

Typical Tensile Properties

Temperature, Degrees F 68 212 392 572 752 932 1112
Ultimate Tensile Strength, ksi 71 62 62 59 51 42 30
0.2% Yield Strength, ksi 35 26 16 13 13 13 11
Elongation, % 42 43 45 48 53 59 68



Invar 42 Specifications: UNS K94100

Chemistry Data

Carbon   0.05 max
Iron   Balance
Manganese   1 max

General Information

Principal Design Features

This is an iron-nickel alloy with controlled thermal expansion properties.

Used for glass-to-metal sealing of components that are enclosed in a glass envelope, such as lamps and electron tubes.

The alloy is readily machinable by conventional techniques.

Ductility and thus formability are very good.

The alloy may be welded by conventional methods.

Heat Treatment
An annealing heat treatment may be used. The alloy is not hardenable by heat treatment.

Forging may be done at 2200 F. As is true of all the high nickel content alloys care should be taken to avoid contamination from sulfur due to long soaking time in a furnace atmosphere.

Cold Working
The alloy has good ductility and is readily cold worked.

Anneal at 1450F (788C) followed by air cooling.

Hardens due to cold working only.


Physical Data

Density (lb / cu. in.)   0.293
Specific Gravity   8.12
Specific Heat (Btu/lb/Deg F - [32-212 Deg F])   0.12
Electrical Resistivity (microhm-cm (at 68 Deg F))   494
Melting Point (Deg F)   2600
Mean Coeff Thermal Expansion   0.8
Modulus of Elasticity Tension   21.5


Kovar Specifications: UNS K94610

General Properties

Symbol: Ni, Fe, Co alloy
Weight Percent: 29% Ni, 17% Co, 53% Fe, 1% trace
Density: 8.36 g/cm3
Melting Point: 2642 Degrees F (1450 Degrees C)
Thermal Conductivity: 16.8 W/mk
Electrical Resistivity: 0.49 microhm-m
Expansion Coefficient: 5 ppm/ Degrees C

Typical Analyses

Chemical Composition

Material / Purity: Kovar
Mn 0.30
Si 0.10
Ni 29.0
Co 17.0
Fe Bal.



The principal precaution to observe in forging is to heat quickly and avoid soaking in the furnace. Long soaking may result in a checked surface due to absorption of sulfur from the furnace atmosphere and/or oxide penetration. A forging temperature of 2000/2150 Degrees F is preferred.

It is important to control heat build up, the major cause of warpage.

One thing of prime importance is that all feathered or wire edges should be removed from the tools. They should be kept in excellent condition by repeated inspection.

If steel cutting tools are used, try a feed of approximately .010" to .012" per revolution and a speed as high as 35/FPM could probably be attained. Some of the angles on the cutting tools would be as follows:

  • End cutting edge angle -Approximately 7 Degrees

  • Nose radius -Approximately .005"

  • Side cutting edge angle -Approximately 15 Degrees

  • Back rake -Approximately 8 Degrees

  • Side rake -Approximately 8 Degrees

When cutting off high speed tools are better than carbide tools, and a feed of approximately .001" per revolution should be used. The cutting tools should have a front clearance of about 7 Degrees and a fairly big tip--larger than 25 Degrees would be helpful.

When drilling a 3/16" diameter hole, a speed of about 40/FPM could possibly be used, and the feed should be about .002" to .0025" per revolution, for a 1/2" hole, approximately the same speed could be used with a feed of about .004" to .005" per revolution. The drills should be as short as possible, and it is desirable to make a thin web at the point by conventional methods. By conventional methods, we mean do not notch or make a crank shaft grinding. It is suggested that heavy web type drills with nitrided or electrolyzed surfaces be used. The hole, of course, should be cleaned frequently in order to remove the chips, which will gall, and also for cooling. The drill should be ground to an included point angle of 118 Degrees to 120 Degrees

Reaming speeds should be half the drill speed, but the feed should be about three times the drill speed. It is suggested that the margin on the land should be about .005" to .010", and that the chamfer should be .005" to .010" and the chamfer angle about 30 Degrees. The tools should be as short as possible, and have a slight face rake of about 5 Degrees to 8 Degrees.

In tapping, a tap drill slightly larger than the standard drill recommended for conventional threads should be used, because the metal will probably flow into the cut. It is suggested that on automatic machines, a two or three fluted tapping tool should be used. For taps below 3/16", the two fluted would be best. Grind the face hook angle to 8° to 10°, and the tap should have a .003" to .005" chamfered edge. If possible, if binding occurs in the hole in tapping, the width of the land may be too great, and it is suggested that the width of the heel be ground down. Again, it is suggested that nitrided or electrolyzed tools be used. Speed should be about 20/FPM.

Please call 800-707-6061 or fax RFQs to 800-707-3439.  We will get back to you ASAP. Thanks.



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