[Farmwelding]

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.

[MinnesotaDave]

Or just weld on AC and it'll be a non-issue

[Farmwelding]

Or just weld on AC and it'll be a non-issue

But 6010 and 7018

[PeteM]

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.

[MinnesotaDave]

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

[Otto Nobedder]

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

Steve

[PeteM]

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.

[Lightning]

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.

[Olivero]

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.

Best Advice Ever!

[olek]

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.

Regards

[bosulli]

Glad this post was on top, as I have come down with a bad case of arc blow. Using a rickity test stand, which uses the weld table for support, for 3g plate practice. About 1.5 inches from top of plate the arc goes out of control, fingernails, then blows out. Try again, it goes out of control, and blows out instantaneously. I noticed a 7018 stub end on weld table which had metal filings standing on end.

I don't know how to apply the solution the instructor did with the shiny metal plate. But, would like to find the Gaussian magnetism app. Is there any other way to demagnetize a weld table? Maybe a need a more substantial test stand.

[Farmwelding]

Well...reducing magnetism is a case by case basis. Arc blow is as much of a science as a nuclear weapon. So many variables so many answers. The trick we used worked on my table but the next two it didn't. One solution is to run one of the beads on AC. Another solution is to wrap the ground cable around the table post(if you have one). Another thing that may work is when you experience arc blow is to change you rod angle drastically but I can't remember if it is more push or pull(someone help maybe?). Like others said though: the only arc blow you'll experience is usually in schools. The reason we assume our tech school has arc blow problems is the wiring. A set of 110 volt outlets and 2 480 volt boxes in all of the like 30 booths. That's a lot of wire with a lot of electricity going through it.

[MinnesotaDave]

Glad this post was on top, as I have come down with a bad case of arc blow. Using a rickity test stand, which uses the weld table for support, for 3g plate practice. About 1.5 inches from top of plate the arc goes out of control, fingernails, then blows out. Try again, it goes out of control, and blows out instantaneously. I noticed a 7018 stub end on weld table which had metal filings standing on end.

I don't know how to apply the solution the instructor did with the shiny metal plate. But, would like to find the Gaussian magnetism app. Is there any other way to demagnetize a weld table? Maybe a need a more substantial test stand.

Try moving the ground clamp.

Some reading on the subject that may help: http://www.lincolnelectric.com/en-us/su ... etail.aspx

[MinnesotaDave]

Well...reducing magnetism is a case by case basis. Arc blow is as much of a science as a nuclear weapon. So many variables so many answers. The trick we used worked on my table but the next two it didn't. One solution is to run one of the beads on AC. Another solution is to wrap the ground cable around the table post(if you have one). Another thing that may work is when you experience arc blow is to change you rod angle drastically but I can't remember if it is more push or pull(someone help maybe?). Like others said though: the only arc blow you'll experience is usually in schools. The reason we assume our tech school has arc blow problems is the wiring. A set of 110 volt outlets and 2 480 volt boxes in all of the like 30 booths. That's a lot of wire with a lot of electricity going through it.

Your electrical theories are wrong.
Arc blow does not only happen in schools....it's part of welding.

[olek]

Hello
6
@farmwelder : too bad it did not work with other tables ..but if you try to read a thesis on remanent magnetism and arc blow (I find some, and you can read only the abstract fof each chapter and the experimentation part , passing formulas and computations) you can obtain causes for arc blow they are mostly in magnetic circuitry .

that relate to mass of metal subjected to a magnetisation by welding , manipulation, earth magnetism...

I do not think electrical wiring ac provide a path for magnetism (plus the wires are not steel I suppose, I can be wrong indeed., where all the tables oriented the same ? (I did read that long pipes could be oriented east west so they do not create antenna fof earth magnetism)

Pro welders say it is not so often, that arc blow is annoying , mostly when welding long thick metal pieces as the ones used for houses building.

To answer for the magnetism app, I have one in my cell phone. The name is "metal detector" but it does react to magnetism. It is a small app in a collection of "measuring tools" but it may be easy to find one similar.

Regards

[bosulli]

I did read the Lincoln article. Very theoretical, which convinces me that magnetism does effect the arc, but not specific enough to tell me how to fix my particular situation. I did move the ground clamp to right of the piece on the horizontal part of stand. At first at I had it directly behind the center of the piece. I will try to attach a pic of the piece on the stand right before I welded this last time. Seems the arc blow was toward the left, as all of sudden as the arc went of control, I had massive undercut to the left, and upon inspection of electrode, there was fingernailing, and flux burnt on one side.

I found a free app at the Apple store. I will try out, if the $$$ apps seem better, I will get one of those.

Sorry pic is sideways. I even flip it over and uploaded again.

[MinnesotaDave]

Try clamping directly to the plate too, various locations.

image.jpeg (29.94 KiB) Viewed 3125 times

[olek]

I did read the Lincoln document. It is not very clear to me but mas be the language barrier.

I noticed it say that nickel is very permeable to magnetism, I have 95%nickel rods that always make an unstable arc, make me think of testing them with the "gaUssmeter" of my telephone, and if clearly magnetized I will try to run the electrode in a de magnetiser tool.

When having arc blow in anew open root joint, numerous tacks will close the circuitry, if not you may experiment that sudden change because the path for magnetism changes as long as both sides get welded
Here is the thesis I get those "hands on experiences" results ( see in the middle after page 125 just the sketches may suffice to understand may be the strenght of magnetism is measured left and right of the electrode during its travel motion from left to right. The different sources are measured individually and the 2 graphs show the result. The sketch show the mass location (s) and the setup ( for instance more draft angle build more arc blow than 80 degree inclination - as suggested there below)

I am sorry that abstract is in English only at the beginning of the publication.

Elsewhere I understand that if I have arc blowing to the left, placing my ground left will reduce it ( and the nearer the better) for a long joint I put it at the beginning of the joint as this is what is considered the 'less bad' solution in that document

Regards

https://www.google.fr/url?sa=t&source=w ... qYKFgtOM7g

[Poland308]

You could also try running a separate ground cable from your work station to a ground rod.

[PeteM]

Eh, just in looking at it, with the backing plate acting as tabs, I wouldn't go straight to arc blow unless there was a great deal of magnetism detectable on that set up. On 3G the most common error which also fits the description of the behavior described is bad electrode angle- too steep. Its always at the top few inches that people start reaching instead of moving their wrist up with the weld. This makes a bunch of heat, bad arc characteristics and looks a whole lot like magnetic blow

Admittedly, I'm a blame the Indian not the arrow guy, so before I go looking into Gauss fields and anything else, I'd be darn sure that the technique is rock solid. Apology in advance if that isn't the case.

If it is magnetic, tacking another piece onto the backing strap will draw the field out a little and should reduce it to a more manageable level.