[weldin mike 27]

Sent to me by a member,

Hey I was wondering if you could answer a question for me. Tonight in welding class i was welding and the rods were sticking really bad, I was using a lincoln precision tig 225 on DC-. Myinstructor came over and said well heres your problem and turned the machine while it was on (I wasnt welding anything right at that moment) to DC+ really fast. So it went from DC-to AC to DC+ really fast while it was on and the negative clamp connected to the table. Later on i noticed that my electrodes and some of the things that were sitting on the table were magnetic. They were picking up small pieces of debris off the ground and the table. Im not sure how this affeted me, if any. I just noticed that new electrodes from the rod oven would become magnetic after being welded with and my file also.I continued to weld for about another after Will this hurt or affect me in anyway??like my heart or anything? It may be a stupid question but I was concerned b/c i know little about electromagnetic fields and all that plus my instructor had no idea why it happened.

[WTFH]

Any time current flows through a conductor i.e. welding cables a magnetic field is created. The amount of magnetism created is dependent on two things, first the amount of current and second if the conductor is coiled. Search magnetic particle testing for more info.
Changing the polarity on that machine shouldn't have changed a thing with regard to the magnetic field. As far as safety, I have never heard anything about concerns with the magnetism created while welding. If you ever weld in an area where a lot of grinding of steel has taken place it is not uncommon to see the iron particles from grinding line up in a pattern around the ground cable if the ground is not being move around a lot.

[dsmabe]

As far as being concerned about the magnetic field, unless you have a pacemaker or anything similar, you don't have anything to worry about. At work I'm constantly around induction heating, which puts off a massive electromagnetic field.

[TRACKRANGER]

The direction of the magnetic field is controlled by the direction of current. Its strength is also determined by the amount of current.

In a DC machine, the current flows continuously in one direction, causing a magnetic field to be created in one direction. In simple terms, the longer time the current flows for, the stronger the magnetic field created. When the current ceases, these items remain magnetized (residual magnetism)

In an AC machine, the current keeps reversing, and therefore so does the direction of the magnetic field. It builds up slightly in one direction, and then this is instantly negated when the current starts flowing in the other direction. Essentially, it has far less opportunity to reach any sort of saturation level. That's the very reason an AC frequency is used in a demagnetizer.

There will always be a magnetic field produced whenever current flows through a conductor. Unless you have a pacemaker fitted, or have had special medical advice to the contrary, you're probably OK.

[WTFH]

AC is used to demagnetize parts because in order to remove a magnetic field from a part you need to change the direction of the field and AC of course does this without having to do anything special like changing DC polarity. Here’s how it works: The left over magnetism or residual is not as strong as when an electrically generated field is being induced. In order to change the fields direction you only need enough magnetism in the opposite direction to slightly overcome the residual field. Once the direction of the original field has been changed an even smaller amount of residual magnetism will remain and therefore a smaller amount of magnetism to overcome and change the residual fields direction. And so on and so on etc. until all of the magnetism is removed.

I have demagnetized countless small parts by using an AC magnetic particle testing yoke energizing it and slowly moving it away from the part.
I left out all of the technical jargon but if you Google Coercive Force in magnetism I'm sure you will get a detailed explanation.