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!
