is Nichrome magnetic ? what is its relative permeability ? - Page 1
Forum section: electronics / general

author: metebalci
author_rank: Frequent Contributor
timestamp: February 27, 2024, 12:44:59 pm
content: I have not been able find the relative permeability of Nichrome (Ni80Cr20) yet. Is it magnetic or not (or negligible mu_r~1) ?

author: Berni
author_rank: Super Contributor
timestamp: February 27, 2024, 01:39:23 pm
content: 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.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.

author: metebalci
author_rank: Frequent Contributor
timestamp: February 27, 2024, 01:50:50 pm
content: Quote from: Berni on February 27, 2024, 01:39:23 pmI will assume non magnetic then, until I see any number for permeability.Quote from: Berni on February 27, 2024, 01:39:23 pmThat is interesting, I didnt know.

author: TimFox
author_rank: Super Contributor
timestamp: February 27, 2024, 03:52:47 pm
content: Nichrome is paramagnetic.Its permeability is hard to find through Google, but a Chinese vendor quotes 1.09 +/- 0.05.My copy of the “rubber bible” (CRC Handbook of Chemistry and Physics) is in storage: you could check it at your library.

author: metebalci
author_rank: Frequent Contributor
timestamp: February 27, 2024, 03:57:10 pm
content: Quote from: TimFox on February 27, 2024, 03:52:47 pmIndeed hard to find. Meanwhile, you answered another question I have, the name of the catalog for material properties, thanks.

author: antenna
author_rank: Frequent Contributor
timestamp: February 27, 2024, 07:35:26 pm
content: a toaster sample (thin wire) and atoaster ovenspace 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.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 27, 2024, 08:32:37 pm
content: 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.pdfthey 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

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 27, 2024, 09:19:23 pm
content: 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.

author: TimFox
author_rank: Super Contributor
timestamp: February 27, 2024, 10:51:03 pm
content: 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 field2. paramagnetism is a much weaker effect (low positive permeability, > +1, where vacuum = +1) that is close to linear without hysteresis, also due to electron spinif you heat a ferromagnet above its Curie point (transition temperature), it becomes paramagnetic3. diamagnetism is another weak effect (low negative permeability, < -1) found in materials such as copper, where the orbiting electrons resist the applied field

author: TimFox
author_rank: Super Contributor
timestamp: February 27, 2024, 10:55:46 pm
content: Quote from: metebalci on February 27, 2024, 01:50:50 pmThe "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 ferromagneticThe "400" series of "martensitic" stainless steels are usually ferromagneticSeehttps://en.wikipedia.org/wiki/Austenitic_stainless_steeland other entries for martensitic, etc.