Round vs square tubing magnetism

Came across this exchange ("Ask the Mechanic") in a farmer-oriented magazine: Q: "..could not get the pipe to weld...pipe was rusty because it had been on
the ground...welder was checked...it was ok." A:"When you said the pipe had been on the ground for several years, you answered your own question....It's a problem fully understood by professional welders...Since the pipe is round, it has the ability to pick up the earth's magnetism, which makes it nearly impossible to weld--it's this repel and attract thing. Square tubing cannot pick up this magnetism, only something round, like pipe... The pipe you purchase needs to be on a rack off the ground... To check the pipe before you buy it, use a hacksaw blade... If it attracts the blade, take your business elsewhere." Never ran into this explanation before, although I, too, have had trouble welding round, rusty pipe. Comments, anyone? Will
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Wrapping one of the cables around the piece can help. If it's worse, change the direction of the wrap or the direction of the length. Seen this done to reduce arc blow.
Steve
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USE AC to degauss.
A car bumper will be magnetized. A square tubing can as well. A pipe and everything else must be aligned to the pole lines and if it moves or switches - it tries to do it in that direction.
The lines in a square tube simply work lengthwise easier than in a circle. They will work in a square. Look at a motor. The windings are nor circular nor are the poles.
I think it is a traditional concept. In the North Slope large pipeline - that one is laid out interesting. MIG or TIG that and you might have trouble. If two pipes (on the ground or flying in the air on wood) will 'fix' to the field that passes through them at a different rate. Likewise alloy comes into play.
Rusty means oxides all over. Hard to get metal to weld to an oxide layer. Look at hot rolled sheet or anything. The scale is oxide. Can't weld to it. Clean off the rust and give it a try.
If there is a magnetic field, then degauss it with AC.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
SteveB wrote:

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"Will" wrote, quoting from printed reply: (clip)Since the pipe is round, it has the ability to pick

^^^^^^^^^^^^^^^^^ Pure BS. The metal was probably thickly coated with rust. The round vs square part is totally bogus. Also, the earth's magnetic field is far too weak to have such an effect.
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I do not think the shape or ground have anything to do with it, but I have noticed that several steel objects lying N-S without being moved over a very long period sometimes seem to be slightly magnetized. One of my vises which is oriented N-S seems slightly magnetized and I suspect that hammering on it may contribute to the effect. I seem to recall from high-school physics that hammering on a steel rod aligned with a magnetic field would tend to magnetize it.
Don Young, USA
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On Tue, 06 Nov 2007 08:21:17 -0800, snipped-for-privacy@krl.org wrote:

Naw, it is the 'lectricity in the wire that does it. Shoot, everbody knows that....
Bruce-in-Bangkok (Note:displayed e-mail address is a spam trap)
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No. Magnets can be a great help in setting up your joints, and they can also help you deal with "arc blow," too. I'm not sure you would want to use them around something like electron beam welding, but as far as I know the only contraindications for us to use them in the shipyard pertains to sensitive magnetic indicators (such as found on remote operated valves).
--
Tin Lizzie
"Elephant: A mouse built to government specifications."-Lazarus Long
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