View Full Version : MAGNET question


bchee
04-02-2011, 02:23 PM
I hope some smart guys on here can answer.
I heated some magnets, and they lost magnetism.

Do they regain full magnetic power if completely cooled, or have they been permanently demagnetized?

I really hope I didn't screw them up.

Buckgnarly
04-02-2011, 02:27 PM
Probably lost the magnetism.

Cliff notes version: The atoms must be aligned (poles) to be magnetic, you let them "move" freely when heated, so no more alignment. Put it in a strong magnetic field and you can remagnetize it.

Garage5.9
04-02-2011, 02:39 PM
Why did you heat hem

StumpXJ
04-02-2011, 02:46 PM
I made that mistake on some rare earth magnets one time. I cut them in half with a cut-off wheel, (think chopsaw) and when I got done 'perfecting' them, all I had was a pile of useless junk. I didnt really think the heat would bother them but they were destroyed.

One of those "lesson learned" deals for me.

Sorry!

bchee
04-02-2011, 03:06 PM
These are rare earth (neodymium) magnets from computer hard drives.
They were glued to brackets.
They came off beautifully with the heat gun.
Now they are really weak.

How do I create a strong magnetic field to remagnetize them?

I have been playing around with them by sliding them against each other to see if that makes them stronger. Then I stuck them all together and put the whole thing in the freezer.

kbs2244
04-02-2011, 03:16 PM
They are toast.

hydramatic
04-02-2011, 03:29 PM
ask George Mizell, The magnet man....supermagnetman.com
Ive bought a ton of mags from him to hold tools in place..he`s got some neat stuff on u tube.

bchee
04-02-2011, 08:32 PM
I sent him an email. We'll see what he says.

mbatarga
04-02-2011, 09:54 PM
The substance is heated to increase it's magnetism. You have demagnetized them.

bchee
04-02-2011, 10:10 PM
yeah, but permanently?

Is there a way to reverse it?

Ritter4.0
04-02-2011, 11:34 PM
This doesn't help your problem, but next time to get the magnets off the brackets. Clamp both ends of the bracket in visegrips, bend the two ends together. The glue holding the magnet on usually gives before the magnet breaks.

Buckgnarly
04-02-2011, 11:41 PM
yeah, but permanently?

Is there a way to reverse it?

Uh, yeah.... as I posted. Realign the atoms/electrons/charges. Introduce a magnetic field powerful enough to realignn the atoms.

stopdroplol
04-03-2011, 02:46 AM
You're pretty much screwed.

You can try getting another magnet (the stronger the better) and rubbing it down the length of the demagnatized one in the same direction. This may or may not work for a rare earth magnet.

The proper way to do it is to put it on a machine that basically a rod and a coil. The magnet attaches to the coil and DC current is sent through the coil and becomes magnetism. I say basically because there's a lot more to it to that. The machine has to be designed and operated right or otherwise the field will just collapse. The only place I know of that would have this machine is a magneto overhaul station and I doubt it's cheap.

Edit: On second thought, Magneto's are not a rare earth magnets so I doubt their machines would even work.

DoyleDee
04-03-2011, 03:55 AM
I found this out the hard way too.... while using magnets to hold the "doors" on my outdoor firepit. I heard the sound of metal (think nickels dropped onto a welding table) and thought "wth was that".... only to find out I ruined them. And yup, rare earth magnets...just about the size of nickels.

dankeenan
04-04-2011, 06:08 AM
Get it warm again, and place it next to a good strong magnet, let it cool down. Sometimes you can get the mag field to line up again.

willy3486
04-04-2011, 07:09 AM
Instead of trying to get these going again just replace them. I work on computers for a living and repair guys have a lot of them dead laying around usually. At work because of the type of data we have I will take the drive completely apart. I pull the magnets and save them. We use them at work all the time to hold screws of stuff while waiting for parts. I have had some luck getting them off of the pieces of metal by tapping them on the side with a flat object. A strike just right will sometimes pop them off. The ones that are on a flat piece I usually use these myself. We used about 4 or 5 when my daughter was in HS band. We would haul a trailer out on the fiels and I made a flagpole and put the magnets on the wooden post. We put the a jolly roger flag on it since their theme was pirates. I never saw it blow off even in 25+mph winds. You would have to slide the pole off since you couldn't pull it off. I have used them to hold pieces of metal together while I welded but I always had to toss them since they lost the magnetism.

Professur
04-04-2011, 08:02 AM
Got hundreds of them here in the lab ... the only ones I try to take off the brackets are the ones with tapped screw holes under the mags. Usually it's the chrome that fails, not the glue. Not that I care one way or the other ... they still get the job done. Leaving the bracket on the others gives me something to clamp to.

MoonRise
04-04-2011, 10:14 AM
Heat a magnet hot enough, and it will lose its magnetic properties.

It is a 'permanent' loss of magnetic power, in that it will not just 'cure' itself or come back.

It is not 'permanent' in that you CAN remagnetize the magnet.

But for 'full power' on a rare-earth magnet (pretty much what ALL hard-drive magnets are made of), you'd have to use a pretty strong magnetic field in order remagnetize the rare-earth magnet.

IMHO, for all practical purposes those (former) magnets are toast. Toss 'em and you learned a lesson about heating magnets up past the Curie temperature.

http://en.wikipedia.org/wiki/Curie_temperature

http://en.wikipedia.org/wiki/Rare-earth_magnet

http://en.wikipedia.org/wiki/Ferromagnetism

Stuey
04-04-2011, 10:27 AM
Yep, they're toasted. As MoonRise posted, above the Curie temp., you more or less randomize the magnetic domains, severely weakening the magnet's strength. It will be difficult to restore its strength using home requipment.

bchee
04-04-2011, 12:03 PM
Thanks for the all the input guys.
I don't know where to find a field strong enough to revitalize these.
I will try what dankeenan suggested in a last ditch effort.

Get it warm again, and place it next to a good strong magnet, let it cool down. Sometimes you can get the mag field to line up again.



This doesn't help your problem, but next time to get the magnets off the brackets. Clamp both ends of the bracket in visegrips, bend the two ends together. The glue holding the magnet on usually gives before the magnet breaks.

Just tried this and the magnet broke in half. What's weird is that it's weaker now, and when I try to put the halves back together, they flip around.
Magnets are fun.

danski0224
04-04-2011, 12:13 PM
ask George Mizell, The magnet man....supermagnetman.com
Ive bought a ton of mags from him to hold tools in place..he`s got some neat stuff on u tube.


Can't even look at his website without registering.

Stupid.