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Arc welding and magnetized objects


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When you work on a metal welding table with all the electric flowing through the electric arc welder (tig, mig etc) cables, can this induce a magnetic field to the metal table, work, support blocks etc ?

If these metal items become magnetized, how does this affect the arc? Will the arc be attracted to a magnetized object?

What can we do to de-magnetize things or should we even worry about it?

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The only time Magnetism will be a problem is when using a DC welder and the phenomenon known as ARC BLOW occures. This is when the molten metal of the weld puddly is drawn from the puddle by the Magnetism phenomenon.

There are several ways that this can be corrected.
1. MOVE the GROUND CLAMP to a different location.
2. Weld in the OPPOSITE direction.
3. WRAP the ground cable several times around the piece being welded.

Trying to tack weld or weld next to one of those strong magnetic helping hands can be an experience too.

On a tour of National Crane one time, I saw on their assembly of the Crane Booms which are a Welded Fabrication. The welds were made with an automated welder on a track and in the Horizontal Position. I was amazed that they had a magnetic strip positioned a certain distance above the weld to keep the Weld Puddle from sagging and thus eliminating a whole lot of finish grinding.

If you happen to be around someone who is Welding with a DC Welder and they have their extra cable coiled up on some form of hanger, watch the coil when the arc is struck and the weld is in progress. If there is any droop to the coil it will suddenly jump out into a more rounder configuration.

During the time the weld is in progress any thing iron close by will be drawn to the coils as this is in fact making an electromagnet. And by holding a piece of iron in the center of the coils the piece can be Magnetised or by holding it in the other coil it can be Demagnitised.

If a DC welding lead is laid in the form of a loop on the table or floor you will notice the iron dust from grinding etc will be gathered in a central pile or be gathered directly under the coil.

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Intersting topic!
You can read more about arc blow and how to avoid it here:

A coil fed by AC current at 50 or 60Hz will not make an electromagnet, because the magnetic field is changing direction all the time and cancels itself in average. With the very high DC currents used in welding, yes, you can create non negligeable magnetic fields.


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