Magnetized welding area

[Olivero]

I was making something on my table today and when I was doing the welds, I would just hold on to the piece with one hand and then hold it down on the table and when I started welding, I felt the piece trying to move away from me (this is DC TIG btw), I have always noticed that I felt a pull or push when doing it this way.

Today I found out it was a magnetic type push as when I went to grab it with my steel pliers, they were pulled in right to the spot I had just welded at on my table, not the piece I was making, But the table below it, that spot right where the weld was, became magnetic. Then I went to a different spot I had been at a few minutes earlier, and it was still magnetic.

Anybody have this happen? Is there a way to avoid it?

[H80N]

I was making something on my table today and when I was doing the welds, I would just hold on to the piece with one hand and then hold it down on the table and when I started welding, I felt the piece trying to move away from me (this is DC TIG btw), I have always noticed that I felt a pull or push when doing it this way.

Today I found out it was a magnetic type push as when I went to grab it with my steel pliers, they were pulled in right to the spot I had just welded at on my table, not the piece I was making, But the table below it, that spot right where the weld was, became magnetic. Then I went to a different spot I had been at a few minutes earlier, and it was still magnetic.

Anybody have this happen? Is there a way to avoid it?

It's called "ARC BLOW"....

Here are some videos about it

https://www.youtube.com/results?search_query=ARC+BLOW

[Aeronca41]

Not the same thing as arc blow with DC SMAW when the work becomes magnetized from the DC welding current but I assume caused by the same principle. Only fix I ever knew with SMAW was switch to AC-not very helpful for Tigging steel, and not easy " way back when " with a DC-only machine out in the field. I'm anxious to see if anyone has a good answer to this-interesting question.

[H80N]

You can always demagnetize it (degaussing)

The easiest way to demagnetize ferrous metals is to pass an AC current through it

Good question.

..... The chance of magnetizing the work is common when running at higher amps. You may have to demagnetize it or try running your ground clamp on one side for awhile then the other side. Or put the clamp as close to your weld area. You can also run AC directly through the part with your stick stinger on one side and the ground clamp on the other side. Turn your unit way down on amps and step on the foot pedal for a short time. This should degauss the part.

Hope this helps.

Andy

http://www.millerwelds.com/resources/communities/mboard/forum/welding-discussions/3653-magnetism

Here is an old thread on it...

http://www.millerwelds.com/resources/communities/mboard/forum/welding-discussions/563546-arc-blow

[Aeronca41]

It's called "ARC BLOW"....

Here are some videos about it

https://www.youtube.com/results?search_query=ARC+BLOW

Interesting-didn't know it was called arc blow in this context-I always thought of that as the actual movement of an arc due to magnetism, but as I said earlier, the source principle has to be the same so there's no reason not to use the same word. Always fascinated by this. Just wish I could see the lines of force as they develop and impact the work-like I always wished i could see the thermals the hawks are riding. There is so much about the world we can't see!

[H80N]

Interesting-didn't know it was called arc blow in this context-I always thought of that as the actual movement of an arc due to magnetism, but as I said earlier, the source principle has to be the same so there's no reason not to use the same word. Always fascinated by this. Just wish I could see the lines of force as they develop and impact the work-like I always wished i could see the thermals the hawks are riding. There is so much about the world we can't see!

You are correct.... i did not explain myself well......Arc deflection (blow) is caused by the residual magnetic field.

if you had a bunch of iron filings.... you could make real mess watching the magnetic lines on DC and the EDDY Currents on AC on your weld table....

[USMCPOP]

Use high AC current and then ramp it down to zero. You then effectively cancel any residual magnetism in a particular polarity in the area of question. Magnet chargers use a pulse in one polarity to do the job of aligning magnetic poles. Could be thousands of amps in one pulse, 20,000 kilo-Joules or more. God help you if you didn't have the potential magnet bolted down.

One place I worked, they were designing a 50 kilo-Joule magnet charger (100 k-Joule?). It would misfire and vaporize the copper wire out of the plastic insulation before it could catch fire. A coil fixture in a 5 gallon bucket on the floor would jump and spill the water. Scary stuff. Even the older 20 k-J chargers the size of a small bar refrigerator with several cases of caps the size of beer cans were called "widow-makers" by the techs.

[ryanjones2150]

You mean, YOU can't see the lines of force as you weld? <br />
<br />
...hmmm...<br />
<br />
Lines of force, see as you weld. <br />
<br />
Maybe you need that helmet thing Obiwon made Luke wear when he was teaching him how to fight with a light saber.

[Aeronca41]

You are correct.... i did not explain myself well......Arc deflection (blow) is caused by the residual magnetic field.

if you had a bunch of iron filings.... you could make real mess watching the magnetic lines on DC and the EDDY Currents on AC on your weld table....

Don't think I haven't thought about the iron filings..... :-)
Just never actually did it-it would be a mess.

Ryan, --Lines of force-that would be cool! If someone would just put that helmet on the market at a reasonable price.....

Interesting this topic came up today. I was welding some tubing this afternoon with the MM200. My MIG gun pliers were laying on the table near one of the welds. When I picked them up, they were almost completely covered with filings from grinding. Thoroughly magnetized, and they still are. The work lead was connected to the table with the tubing clamped down tightly. The pliers were between the work lead and the weld. Voila! Magnetized, and pretty strongly.

USMCPOP, you've done some scary stuff! I spent a lot of time in my career trying to get rid of emi and stray magnetic fields while you were busy making it

[H80N]

I spent a lot of time in my career trying to get rid of emi and stray magnetic fields while you were busy making it

Been there.....

High speed analog and digital signals... plus power/ground bus routing

Ground loops are not just for taildraggers.... gotta kill them in the circuit (and board) design stage.... otherwise....

strange Emi/Rfi happenings.. Twilight Zone.....

[Aeronca41]

Strange indeed. Black magic. Many stories, some with expensive endings-those design stage issues...found in final test, or worse, in the field at installation. But we won't hijack this thread! Far easier to deal with magnetized tables and pliers.

[H80N]

Strange indeed. Black magic. Many stories, some with expensive endings-those design stage issues...found in final test, or worse, in the field at installation. But we won't hijack this thread! Far easier to deal with magnetized tables and pliers.

that interaction can be "FM".....add in temp... shock & vibe...

but I digress....

as you said..... back to magnetized pliers and stuff....