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Eliminating Arc Blow

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Eliminating Arc Blow

Postby Farmwelding » Fri May 05, 2017 1:36 pm

So last night I experienced arc blow for the first time on a t-joint. Told the instructor and he went away and came back with some 5/32" 6011s, a c-clamp vise grip and a 5"x5"x1/4" shiny plate and a piece of paper with instructions. He pulled out his phone (samsung) and opened a gaussian reader? and moved it around. The table was around 35 until the corner where I had arc blow and that was at around 180. So he clamped the plate to the table and placed the ground on the other side of the table away from the plate. (This was the first time he had done this as well) Flipped the dynasty 200 to AC and 200 amps, (as high as the machine goes or the highest amperage the rod will take)Then you short the electrode to the plate until the rod disintegrates or if it wont stick like ours didn't keep going until it goes through the backside. Stop the current and then take another reading. This table dropped down in one try to the 35 like the rest of the table. If it doesn't work the first time or it doesn't do enough, continue moving the earth clamp around.

Maybe some of you old timers have heard of this, but I thought it was really cool and a great experiment with electricity and a way to eliminate that awful arc blow.
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Re: Eliminating Arc Blow

Postby MinnesotaDave » Fri May 05, 2017 2:24 pm

Or just weld on AC and it'll be a non-issue :D
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Re: Eliminating Arc Blow

Postby Farmwelding » Fri May 05, 2017 2:59 pm

MinnesotaDave wrote:Or just weld on AC and it'll be a non-issue :D

But 6010 and 7018
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Re: Eliminating Arc Blow

Postby PeteM » Fri May 05, 2017 3:18 pm

That is degaussing.

There are some good illustrations of fields and lines of magnetism on wikipedia, but moving the clamp will help with magnetic arc blow. Even just butting a piece of scrap to the end will shift the field enough that it is manageable. Main thing we were taught is to flip the stick from a pull to a push at the last inch of weld, so that the arc force is pushing back against the magnetic blow. Also, if your bead is always sagging out in the middle of the joint, lay the stick down a little. There is another field in about the center of the piece that can cause that.

FWIW- I've never run into it as a serious problem outside of a booth. It can be a problem with SAW, but they'll often run one gun AC 2 DC or something along those lines, and have run offs or tabs that shift the field.
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Re: Eliminating Arc Blow

Postby MinnesotaDave » Fri May 05, 2017 3:50 pm

Now that you've experienced it, try some of these concepts from Lincoln the next time and see how it turns out.

http://www.lincolnelectric.com/en-us/su ... etail.aspx
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Re: Eliminating Arc Blow

Postby Otto Nobedder » Fri May 05, 2017 7:49 pm

In WWII, degaussing was applied to entire ships, in order to defeat magnetic proximity mines. It's still used today.

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Re: Eliminating Arc Blow

Postby PeteM » Fri May 05, 2017 7:59 pm

Otto Nobedder wrote:In WWII, degaussing was applied to entire ships, in order to defeat magnetic proximity mines. It's still used today.

Steve


That is a cool bit of information I wouldn't have thought of. My dad had a particular set of screwdrivers and a degaussing tool he used on sensitive electronics equipment. Those were his "don not touch" tools.
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Re: Eliminating Arc Blow

Postby Lightning » Sun May 07, 2017 8:28 am

Farmwelding wrote:Flipped the dynasty 200 to AC and 200 amps, (as high as the machine goes or the highest amperage the rod will take)Then you short the electrode to the plate until the rod disintegrates


I bet that's good for the Magic Smoke seals in the Dynasty!

No thanks

Why not just – I dunno – drop the Dynasty into a bucket of seawater while you're welding? I bet that stops the arc blow, too.
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Re: Eliminating Arc Blow

Postby Olivero » Tue May 09, 2017 12:50 pm

Lightning wrote:
Farmwelding wrote:Flipped the dynasty 200 to AC and 200 amps, (as high as the machine goes or the highest amperage the rod will take)Then you short the electrode to the plate until the rod disintegrates


I bet that's good for the Magic Smoke seals in the Dynasty!

No thanks

Why not just – I dunno – drop the Dynasty into a bucket of seawater while you're welding? I bet that stops the arc blow, too.


Lol. :lol:

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Re: Eliminating Arc Blow

Postby olek » Sun Jun 04, 2017 5:33 pm

from some thesis on arc blow and remanent magnetism, I understood that mass location can help by pushing from it toward the electrode (and the nearer the better) but the big part of arc blow is due to the magnetic circuitry in the piece you weld plus its support.

I was said "put the mass where the blow comes from" as a basic trick .
if that can be tested with a cell phone it is excellent.

evaluating the path that magnetism will follow is not so easy but we can avoid the biggest mistakes as having the mass far on a long piece of metal (that can also make an antenna for earth magnetism)

it seem to be find that one have less trouble when welding a lenght of weld, to have the mass a the begin. (less effect than at the end) . to use multiple solder points to close the magnetic circuitry when welding an open root, a double mass may be useful but the arc induced magnetism is only 30% of an arc blow generally.

the degaussing trick and testing with cell phone are interesting, thanks for sharing those.

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