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bosulli
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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
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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.
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Nick
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bosulli wrote: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
Dave J.

Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

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Farmwelding wrote: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.
Dave J.

Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

Syncro 350
Invertec v250-s
Thermal Arc 161 and 300
MM210
Dialarc
Tried being normal once, didn't take....I think it was a Tuesday.
olek
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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
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bosulli
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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.
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Try clamping directly to the plate too, various locations.
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Dave J.

Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

Syncro 350
Invertec v250-s
Thermal Arc 161 and 300
MM210
Dialarc
Tried being normal once, didn't take....I think it was a Tuesday.
olek
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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
Last edited by olek on Fri Jun 09, 2017 5:08 am, edited 1 time in total.
Pianos , restorer and tuner
Dedicated to learn welding since april
slowly learning ;) not complaining of doing beads and beads
pro inverter PROGYS 200 FV PFC CEL+tig lift
OA Oxyflam 1000 cutting and welding gas torch
Poland308
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You could also try running a separate ground cable from your work station to a ground rod.
I have more questions than answers

Josh
PeteM
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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.
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