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Bizarre MIG phenomenon

Posted: Thu Aug 29, 2013 7:05 pm
by melrel
Hey guys, I am new to both MIG and TIG welding and was asked by my boss to make some wall brackets to give me some practice but they were also a contracted job. Just a square angle made of 3mm mild steel 30mm wide with a support brace across the angle. (I guess there's a technical name for this - sorry) I produced quite a nice weld on part of the bracket (for a newbie that is) but on another part the weld was diabolical. I had to grind it out and start again. I put the error down to my incompetence and began again. Same thing happened. After a couple more tries, I accidently stumbled across the problem. The magnets I used for positioning the brace were affecting the gas flow from the torch. As soon as I removed the magnets . . . . . . hey presto, really presentable welds.

Please explain . . . . . thanks

Re: Bizarre MIG phenomenon

Posted: Thu Aug 29, 2013 8:28 pm
by Otto Nobedder
I'll take a stab...

I only use magnets during tacking (and feel blessed when I can, as I often weld stainlees), and remove them.

When you arc weld (Mig, Tig, doesn't matter), you're creating an electric arc with a surface temerature of around 11,000 degrees. Your gas becomes plasma when exposed to that temperature, and plasma is deflected by magnetic fields, leading to wierd effects with your gas flow.

Also, don't let your magnets get hot. They will lose strength.

Steve S

Re: Bizarre MIG phenomenon

Posted: Thu Aug 29, 2013 11:13 pm
by JDIGGS82
you're a pretty smart feller otto

Re: Bizarre MIG phenomenon

Posted: Fri Aug 30, 2013 3:13 pm
by melrel
Hey Otto, thanks for this. I'll remember your pointers in future.