Full Transcript:

What’s up guys? Happy Thanksgiving this week to those that celebrate it here in the US. This is Michael with Michael Talks Metal back for more metal musings. Today our video is about one of the Iron-Nickel – Cobalt alloys that exhibit  low thermal expansion characteristics  as compared to many other metal alloys and similar to some glass and ceramics.  Most commonly known as Kovar when produced by Carpenter technology, its UNS designation is K94610.

Metals typically expand with rising temperature  and conversely shrink with decreasing temperatures.  The rate at which this occurs is called the Coefficient of Thermal Expansion or  “CTE”. It  varies with temperature.  To make things easier to use; Metallurgists give us the Mean CTE for a specific range of temperature. With this information we can either compare materials or we can calculate the change in dimension that would occur with a specific change of temperature.

As an example, Kovar has the following mean CTE:

Room temp  to   212  deg F   ……………… 3.25 micro inch per inch per degree F

Room temp  to   750  deg F  ……………….. 2.81 micro inch per inch per degree F

In other words, a 10 inch length of Kovar heated from room temperature to 212 deg F would increase in length  3.25 (CTE) X 10 (length) X 140  ( 212 F – 72 F)  which equals an increase of only  point 0045 inches. For those of you doing the math at home, a micro inch is a millionth of an inch;  10 to the minus 6 in scientific notation.

Applications are typically for parts that form a glass or ceramic seal.

Nominal Chemical Composition:   UNS K94610

Carbon …………………………………………………. 0.02% Maximum

Silicon  …………………………………………………..0.20 %

Manganese ……………………………………………. 0.30 %

Cobalt …………………………………………………… 17.0 %

Nickel ……………………………………………………  29.0 %

Iron  ………………………………………………………. Balance

Is Kovar Magnetic? Yes, Kovar is Magnetic.

Curie Temperature:     815 Deg F

Density:   point 302 lbs per cubic inch

Typical Mechanical Properties in the annealed condition:

Tensile Strength:     50,000 psi

Yield Strength:         75,000 psi

Elongation:                30 %

Hardness:    68   Rockwell B

Specifications:

ASTM F-15

As we have told our viewers many times before, specifications, prints,  and part requirements can add to or alter the information we have presented to you today….so it’s been 62 times since we started tell you to…CHECK THE SPECS. Michlin Metals is a supplier of and distributor of Kovar. Any more questions make sure to visit us at or website… michlinmetals.com. Thanks for tuning in and if you made it this far and haven’t subscribed please consider doing so now, if you missed last weeks video, click here. Thanks again, this is Michael with Michael Talks Metal, see you next Thursday 10am! I’m out.