General > General Technical Chat

is Nichrome magnetic ? what is its relative permeability ?

<< < (2/2)

antenna:
a toaster sample (thin wire) and a toaster oven space heater sample (the thicker stuff), both clinging to a magnet.  Sorry about the image rotation, my computer always does that to pictures from my phone.

T3sl4co1l:
Hmm, wouldn't be surprised if toasters use stainless or whatever cheap alloy they can find at the time; if it can handle temperature and has resistance, that's more than good enough.

Afraid I don't have any pieces of known alloy/composition, but I can tell there is very slight magnetism to this ribbon-wound Milwaukee (now Vishay) vitreous-enamel power resistor.  Setup is, hard drive (NdFeB) magnet dangling from a ~0.5m clip lead; waiting for it to settle, then moving the resistor up close, gives a displacement of maybe ~2mm when touching.  It's very slight, though I don't know how to convert that to permeability exactly.

This kind I think: https://www.vishay.com/docs/31807/rbefrbsf.pdf they list three possible materials however, so it might not even be NiCr.  CuNi is apparently "nonmagnetic" so it's probably not that (though how nonmagnetic it really is, doesn't seem to be common knowledge; I see some cryogenic-focused papers showing para/ferro magnetism at low temperatures).

Another ribbon-wound resistor (unknown brand) shows noticeable magnetism, I would say comparable to mildly-worked stainless; a wire-wound resistor shows none.  Probably I have a range of materials here... interesting.

Tim

CatalinaWOW:
Finding what alloy you have may be as challenging as finding the permeability.  I don't have any samples at hand, but in the past have fought assembly of small bits and pieces of things that were claimed to be Nichrome because they were so magnetic.  But I have no pedigree on what they actually were.

TimFox:
Note that there are three possible magnetic properties for a given alloy:
1.  ferromagnetism is a very strong effect (high positive permeability), non-linear (variable permeability >> +1), that shows hysteresis, where electron spin magnifies the applied field
2.  paramagnetism is a much weaker effect (low positive permeability, > +1, where vacuum = +1) that is close to linear without hysteresis, also due to electron spin
       if you heat a ferromagnet above its Curie point (transition temperature), it becomes paramagnetic
3.  diamagnetism is another weak effect (low negative permeability, < -1) found in materials such as copper, where the orbiting electrons resist the applied field[/li][/list]

TimFox:

--- Quote from: metebalci on February 27, 2024, 01:50:50 pm ---
--- Quote from: Berni on February 27, 2024, 01:39:23 pm ---Manufacturers of nichrome say it is non magnetic on the internet. Some say it is faintly magnetic.

Something being magnetic or not can be quite complicated. Nickel in itself is feromagnetic, but just because a alloy has a feromagnetic element in it does not automatically make the alloy also feromagnetic.

--- End quote ---

I will assume non magnetic then, until I see any number for permeability.


--- Quote from: Berni on February 27, 2024, 01:39:23 pm ---For example stainless steel is mostly iron, yet most kinds of stainless steel are pretty non magnetic. To make things even weirder, some kinds of non magnetic stainless will become magnetic once you stress it by bending it. You can see this effect on stainless steel forks or spoons, magnets don't stick to the handle, but they do stick to the eating end due to having gone trough pressing into shape.

--- End quote ---

That is interesting, I didnt know.

--- End quote ---

The "300" series of "austenitic" stainless steels have a crystal structure that is usually not ferromagnetic, but when work-hardened the disruption of the structure can become ferromagnetic
The "400" series of "martensitic" stainless steels are usually ferromagnetic

See  https://en.wikipedia.org/wiki/Austenitic_stainless_steel  and other entries for martensitic, etc.

Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod