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RussZHC
06-26-2010, 11:53 AM
I have found so many good ideas from the threads here but have a bit of a dilemma with "conflicting" information, more of a '..but then how does it work...' question.

In using magnets for work holding when welding/brazing, how does the magnet(s) continue to function given the possible relative high range of heat very nearby?

Most information in supplier catalogs cautions that temperatures over 200*F have an effect of the ongoing magnetic pull (that is for rare earth magnets, "regular" magnets rarely have such info) so, as example, if you were welding a 90* angle very close to the corner would the heat not be enough to have an effect on the magnetism?

Or am I missing something very, very obvious? I think I can understand if welding the HAZ could be relatively small, in fact would be, but what about for brazing?
If you have very small parts the "air gap" larger parts would have in the held arrangement all but disappears.

vpt
06-26-2010, 11:56 AM
I don't know about brazing but if you get close to a magnet while TIG welding the magnet will pull on either the filler or the TIG arc and mess up the weld. I don't use magnets any more for welding, I got myself a whole collection of different clamps.

Black_Moons
06-26-2010, 12:44 PM
Usally the magnets iv seen are recessed at the corner, And basicly all say 'for tack welding ONLY'

I think the idea/proceedure is you just tack weld em while held by magnets, remove the magnets, double check straightness, Pound on it with a BFH (big f...friendly hammer) to realign it, then do the full welds.

cuslog
06-26-2010, 01:21 PM
I too have found that a TIG arc goes "goofy" if its near a strong magnet.
Never tried with MIG or gas welding.

Black_Moons
06-26-2010, 01:24 PM
Oh yea, Random magnet tip:

A brass wire brush (manual or drill style) is just violent enough to get debrie off those welding magnets (without just pushing it around the magnet)

macona
06-26-2010, 03:55 PM
Magnets and materials have a curie temp. Once you go past the curie point on a magnet its all over for it.

Dont feel like explaining it so here's the wiki:

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

mf205i
06-26-2010, 04:05 PM
Oh yea, Random magnet tip:

A brass wire brush (manual or drill style) is just violent enough to get debrie off those welding magnets (without just pushing it around the magnet)
A shot of compressed air also works well.
Mike

lost_cause
06-26-2010, 08:28 PM
i'm not sure on the magnetism loss from heat or altering the arc, but since the magnet often gest in the way anyways, i use them only for setting a 90 or 45 degree angle to tack weld with. i remove the magnet and verify/adjust the angle (aforementioned bfh), and then tack a scrap strap of metal on to make a knee brace, but with a few inches clearance to weld under the brace. add more braces if a long piece. the welding will certainly draw the metal in one direction or the other, but the brace will help prevent it more than anything else will.

Your Old Dog
06-26-2010, 10:44 PM
I have them and use them a lot for mig welding. Mostly they only are needed for the first few welds. In fact if you don't do some balanceing runs the magnets are not strong enough to prevent heat distortion.

J Tiers
06-26-2010, 10:51 PM
In using magnets for work holding when welding/brazing, how does the magnet(s) continue to function given the possible relative high range of heat very nearby?

Most information in supplier catalogs cautions that temperatures over 200*F have an effect of the ongoing magnetic pull (that is for rare earth magnets, "regular" magnets rarely have such info) so, as example, if you were welding a 90* angle very close to the corner would the heat not be enough to have an effect on the magnetism?




it's simple......

if the magnet still works, IT did not get too hot.

No matter what is going on over at the welding area, so long as the magnet itself does not get too hot, it will not be affected.

yes, the neodymium magnets may start to lose their "pull" at a very low temperature. That tends to be the very strongest ones, which are particular mixtures of ingredients. But some formulas are much more heat resistant, yet still have the "neo" advantage sufficiently pronounced to make sense over a regular one.

I would suspect that a "neo" would not be the best choice for welding, because most all of teh strong ones are affected by fairly low temps. But by using pieces of steel in between, etc, you can do a good job of keeping them cool, by design of the "clamps".

PeteF
06-26-2010, 11:03 PM
I don't know about brazing but if you get close to a magnet while TIG welding the magnet will pull on either the filler or the TIG arc and mess up the weld. I don't use magnets any more for welding, I got myself a whole collection of different clamps.

Oh man I'm glad you guys posted that. I thought it was just me! :eek: Certainly makes sense though.

Fasttrack
06-26-2010, 11:55 PM
Oh man I'm glad you guys posted that. I thought it was just me! :eek: Certainly makes sense though.


It certainly does. The arc is a stream of plasma, or ionized gas. Charged particles interact with magnetic fields - specifically, they experience a force perpindicular to their velocity. So the plasma "bends" when it sees a magnetic field.