How to identify mu metal?

[rock soderstrom]

Hey Folks, I have already asked this elsewhere in the forum, but have not received an answer. How can I identify mu metal?
Are there clear indicators for a layperson without special equipment?

Cheers

 

[gyraf]

The only, slightly sad, indicator I have is that if you cut yourself on the material's notoriously nasty edges, there is a very high risk of inflammation - much higher than with just about anything else that can hurt you in the workshop....

Perplexity can't come up with anything better, I think..

/Jakob E.

 

[KrIVIUM2323]

Some guitarist with dreadlocks playing a 7 strings, with a bassist with dreadlocks playing (at least) a five strings, a drummer ( with dreadlocks and double kick drum) thinking he is a metal head, and a singer ( with dreadlocks) thinking he is a rapper...

My bad! I didn't read carefully enough... Mu metal, not Nu metal...

Sorry for off topic i couldn't resist.

On topic:
Some alloy analyzer exists but i fear they cost an harm and a leg. Maybe trying to generate some nastys and see if metal have some shielding properties?
A single coil guitar pickup with neon light above could work from recent recording i've done of stratocaster...

Trying to drill it? High nickel alloy will destroy the drill bit 99% sure.

 

[CJ]

Put it in the Varian 360 MS and look for a wave length if 10.87 Angstroms.

Or use a magnet, if mu metal the magnet will pull on it hard then loose strength as the mu metal rapidly saturates.

Or cut a razor blade sized slice and put it in your shaver, if it is mu metal you will have a close shave and a severed jugular vein if it contains 4% Cobalt.


.

 

[rock soderstrom]

Perplexity can't come up with anything better, I think..

Trying to drill it? High nickel alloy will destroy the drill bit 99% sure.

Thanks guys for your answers. This is was Perplexity says about this topic. (incl. drill test!) As expected, it is not quite so simple, but you can already narrow it down with it...

Identifying mu-metal without specialized equipment can be challenging, but there are a few indicators that a layperson can use:

1. Composition: Mu-metal is primarily composed of nickel (around 75-80%) and iron (12-15%), with small amounts of copper, molybdenum, and other elements[2]. However, this composition alone is not a definitive indicator.

2. Magnetic properties: Mu-metal is highly permeable to magnetic fields. You can test this by bringing a strong magnet near the metal. If it's mu-metal, it should strongly attract the magnet[2].

3. Drilling test: A practical method to identify mu-metal is to attempt drilling a hole in it. Mu-metal is extremely hard to drill due to its high nickel content. If you use a sharp, high-quality HSS drill bit and it gets damaged or struggles to penetrate the metal, it's likely mu-metal[1].

4. Appearance: Mu-metal typically has a dull gray color, similar to other nickel alloys. However, this alone is not a definitive indicator.

5. Thickness: Mu-metal is often used in thin sheets for magnetic shielding, so if you encounter a very thin, flexible metal sheet used in electronic equipment, it could be mu-metal[2].

6. Application: If you find the metal used in specific applications like shielding for transformers, hard drives, or sensitive electronic equipment, it's more likely to be mu-metal[2].

It's important to note that these methods are not foolproof, and definitive identification may require professional testing or specialized equipment.

Citations:
[1] https://www.diyaudio.com/community/threads/testing-mu-metal.332724/
[2] https://en.wikipedia.org/wiki/Mu-metal
[3] https://www.epa.gov/system/files/do...physical-techniques-at-contaminated-sites.pdf
[4] https://faculty.ksu.edu.sa/sites/default/files/Metal Identification Ready _unprotected.pdf
[5] https://indico.ph.tum.de/event/4524...tachments/3450/4190/small_magnetic_fields.pdf
[6] https://monoskop.org/images/5/55/Frutiger_Adrian_Signs_and_Symbols_Their_Design_and_Meaning.pdf
[7] https://domadia.net/blog/understanding-mumetal-a-complete-tutorial-on-properties-and-applications/
[8] https://www.researchgate.net/public..._of_stray_fields_down_to_the_nano-Tesla_level
[9] https://www.magnetic-shield.com/mumetal-technical-data/
[10] https://diydrones.com/profiles/blogs/mumetal-testing

 

[rock soderstrom]

Put it in the Varian 360 MS and look for a wave length if 10.87 Angstroms.

Unfortunately, my Varian 360 MS at home keeps blowing my 16A room fuse, so this test is not possible.

Or use a magnet, if mu metal the magnet will pull on it hard then loose strength as the mu metal rapidly saturates.

okay, I will test that. (I have done it, known Mu metal as well as other possible materials are very magnetic, I can not see any saturation)

Here are a few examples of materials that I would like to test:

Shielding material for a input and mains transformer



or this very soft sheet metal. You can find it in old tube R2R recorder, where it is wrapped around the V1 tube (usually an EF86). This metal feels a bit like lead sheets which is used to seal roofs.

 

[CJ]

Ollie scored a boatload when Funkenwerk was in Seattle,

He got it at a Boeing surplus sale in big sheets, had to bend it for V series transformer cans which reduces the shielding qualities a bit but with a double can it works pretty good,

I don't know what Boeing used it for, maybe to shield the inertial navigation or other electronics.

 

[warpie]

I have seen some Carnhill mu-metal transformers painted in blue/ red/ etc... and I wonder whether ther're really mu-metal cans of some other material.

 

[DaveP]

I can confirm it is very sharp when cut and it has that dull grey sheen surface, you can also solder a wire to a corner to earth it. I doubt it would come in many other forms than sheet, because of the expense. It is so much more effective than steel, there is no need for something thicker, also two layers are always more effective than one thick one, because of the losses going from one medium to another.
best
DaveP

 

[DaveP]

This is the best image of what it looks like:-

I have never seen it look like shiny chrome tape.
best
DaveP

 

[CJ]

Often interleaved with copper sheet, so 3 layers of mu, 2 layers of copper or sometimes brass,

The mu handles the H field and the copper the E field.

Both vector fields must be expressed vectorally in the explicit form as follows:

(Completion of post left to the student as an exercise)

 

[capacitorless]

It's got μ stamped on it?

 

[ccaudle]

had to bend it for V series transformer cans which reduces the shielding qualities a bit

I thought bending reduced the permeability a lot, and you had to anneal it (in a hydrogen atmosphere) again to get back to high permeability.
Has the decrease in permeability after working been overstated?