Full Transcript:

What’s up guys?!?!?! This is Michael with Michael Talks Metal back again to talk INVAR-iably about INVAR! (See what I did there?) Thanks for watching, please consider subscribing and if you like the content, SMASH that like button and help support the channel.

Today our video is about one of the Iron-Nickel alloys that exhibit  low thermal expansion characteristics as compared to many other metal alloys. Most commonly known as Invar 36  when produced by Carpenter technology, its UNS designation is K93601.  Free cutting Invar 36  has UNS designations K93050. The rate  of thermal expansion is roughly one tenth that of carbon steels at temperatures up to 400 deg. F

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  typically varies with temperature in a non-linear manner.  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, Invar 36 has the following mean CTE:

Room temp  to   200  deg F   ……………… 0 .720 microinch per inch per degree F

Room temp  to   300  deg F  ………………..1.170 microinch per inch per degree F

In other words, a 10 inch length of Invar 36 heated from 70 deg F to 200 deg F would increase in length  .720 (CTE) X 130 (length) X 140  ( 200 F – 70 F)  which equals an increase of only  point 00094 inches. Just under a thousandth of an inch 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 require dimensional stability over a range of temperatures.

They can also be used along with a high expansion alloy to create motion for bi-metallic thermostats and other temperature regulators

 Nominal Chemical Composition

INVAR 36        UNS K93601 / K93603

Free Cutting INVAR 36   UNS  K93602 / K93050 *

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

Silicon  …………………………………………………..0.20 %

Manganese ……………………………………………. 0.35 %

Nickel ……………………………………………………  36.0 %

Iron  ………………………………………………………. Balance

*Free Cutting INVAR 36  adds 0.20% Selenium

Is Invar 36 Magnetic? Yes, Invar 36 is Magnetic

Curie Temperature:     535 Deg F

Density:   point 291 lbs per cubic inch

Typical Mechanical Properties in the annealed condition:

Tensile Strength:     40,000 psi

Yield Strength:         65,000 psi

Elongation:                35 %

Hardness:    70   Rockwell B

Specifications:

ASTM B 753

ASTM F 1684

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  CHECK THE SPECS for the 63rd TIME SHEESH!!!! Also, if you need more info on Invar 36 check out our website… michlinmetals.com. Michlin is a supplier and distributor of Invar 36. If you made it this far and haven’t subscribed please consider doing so now, click here. If you missed the most recent upload, click here! Thanks for watching, this is Michael with Michael Talks Metal, I’m out!