drawing on my old electronics background..."cough cough cough" " lots of cobwebs back here"
The only reason I can think of as far as "welding with High Frequency" is 1. magnitization of any metal object 2. a light induced static charge. ANY ferrous metal object subject to long exposure to high frequency will become slightly magnetic... the magnitisim comes from electromagnetic activity from an induced charge. If you are working in a bomb factory or amunition plant I would take it VERY seriously...in a weld shop...its a dust catcher.
Any time you pass electrical current through a conductor you WILL generate a magnetic field. The stronger the current the stronger the field. However in ferrous metals that magnetic field can take up a temporary residence over prolonged exosure. Now what happens when you pass a conductor thru a magnetic field...it generates electricity or voltage in that conductor....if that conductor leads to earth or ground then you will have current, So there is potential for a spark or an arc in ferrous metals exposed to high frequency ...no matter how unlikely there is a chance.
If you are passing radio waves (high freq) signals thru a metal you are causing electrons to bump into each other....you may move some in the metal and cause a charge to build up as well as residual magnitism.....if they are grounded to earth ground....this cannot occur.
Enough exposure to this can cause electronics to go haywire, cd players change track, radios lose thier programming, watches cease to work, mp3 players shut off for no reason etc etc.
Jeez what is it doing to our bodies and brains????!!!!
I hope that was a good explanation and I did not sound all pompous and stuff ....I hate that.
Tommy