This old rookie learned something new today

handirifle · Jul 23, 2014

You experienced welders will most likely pick up on my problem as you read it, but hopefully some other rookie will learn the EASY way.

I have been tasked with a sizable chore at my church. I was asked if I could weld a ramp, not one for handicapped, but for our nearby café. The girls that run the café have to push supply carts about 100yds to get into a room that is only about 30yds from the café, because the nearest entrance is steps only, and the handicapped ramp is the only access they have.

So I have built a 12' ramp and new hand rails that match the angle of the ramp. I am almost done, working on the vertical 1/2" x 1/2" pieces with the decretive knuckles on them. That's a butt load of welding. I was having trouble getting my lengths for the 1/2" tubing cut to proper lengths (DUH!) and I was using magnets to hold them in place while I tacked them on and finished filling in the big gap I created with the lousy measuring.

It seemed like sometimes I had a problem, sometimes not, very confusing. What was happening was when I started to tack, the welding arc would BLOW AWAY from where I was trying to put it. I tried adjusting wire speed, re-cleaning the ground connections, changing heat settings. It was freaking me out. Then (it seemed like) all of a suddenly worked fine. I was really confused. Needless to say, my welds that I did get, looked like crap.

I was using my arrowhead magnets and my magnetic ground.

Then I moved my magnetic ground from one weld, and all of a sudden the arc looked perfect, or as close as I am capable of perfect. Then the light bulb came on!!!!

It was the MAGNETS!!!! Good grief, I have no idea why, I am sure you guys do, but that was driving me absolutely crazy.

Can someone tell me why? I am guessing it was reversing my polarity, but that was really weird. It was like using a nozzle on a water hose, holding it out in front of you pointing AWAY and spraying, only to have the water come back at you.

MinnesotaDaveChalmers · Jul 23, 2014

It's called arc blow - here is my favorite video on the topic.

During the third minute they actually show an arc being deflected.
(It's a stick welding video, but it's still an excellent description of the phenomenon)

https://m.youtube.com/watch?v=CW7I-ymfINU

Shield Arc · Jul 23, 2014

I fought arc blow all my life splicing pile. You had an easy fix. Not so easy for us on the job site. Few ways around it: Switch to AC, which we never had that option, because we only used engine drives. Heat the weld zone to a dull red color, and let cool. Smack the weld zone with a hammer. Wrap your ground clamp lead around the object being welded, if that doesn't work reverse the direction of the wrap. If none of this works, you have to learn to live with it!

FarmDad · Jul 23, 2014

This is why i love my old miller legend engine drive . It has AC as well as DC arc. Some days it seems every piece of steel i weld is magnetized ( and it likely is because my scrap pile dates from the 1940s )

dragoneggs · Jul 23, 2014

MinnesotaDaveChalmers said:
It's called arc blow - here is my favorite video on the topic.
During the third minute they actually show an arc being deflected.
(It's a stick welding video, but it's still an excellent description of the phenomenon)

https://m.youtube.com/watch?v=CW7I-ymfINU

Thanks for sharing this video... very informative and nostalgic too!

roadhunter · Jul 23, 2014

I've ran into that a bunch using old sucker rod on projects. Sounds like you have a much easier way to fix it by simply moving the magnets.

MinnesotaDaveChalmers · Jul 23, 2014

dragoneggs said:
Thanks for sharing this video... very informative and nostalgic too!

You're welcome

Often I find the old videos are excellent - like the "Mr. Shrink" video - another oldie that everyone that welds should watch

http://youtu.be/2vuGlcbDwKY

k0ua · Jul 23, 2014

MinnesotaDaveChalmers said:
You're welcome

Often I find the old videos are excellent - like the "Mr. Shrink" video - another oldie that everyone that welds should watch

http://youtu.be/2vuGlcbDwKY

A good video. I learned most of these things "the hard way", and Jodi helped (welding tips and tricks), but the video explained it well.

Arc weld · Jul 24, 2014

When using DC current there can be magnetic fields built up in the electrical circuit. Arc blow doesn't usually occur until you get up around 180 or more amps. Sounds like on your project the magnets were enough to effect it at much lower amps.

handirifle · Jul 24, 2014

Wow a bigger issue than I thought. The ground magnet is pretty strong and my little 110v Mig only hits 90 amps, on a good day. Seeing that I was using a 100ft 12ga extension cord, plugged into an outlet that was wired with who knows what gauge wire, I was probably lucky to get 65-70.

Moving that magnet sure made a difference.

Thanks for the tips on how to try and overcome it, should I run into a similar issue later on. At least now I know what caused it.