Good writting .. The beam wasnt insulated was it ? Heat loss over large area ...
I did the F-111 wing pivots ( yeah , all by myself ! ) . Many passes with TIG and.035% carbon wire . But induction heating w/ large cables over the 5 inch steel "arms" . Even had to heat them "down" hours after welding ....
Political ? I had to grind out most of the weld ! And that was before X-rays !!! Not after ! We never found any reason to grind out more , after vuing X-rays .
Magnetic fields heat iron by hysterisis , that will cause currents because the switching magnetic fields will force electrons . Its one or the other . If electrons are forced in iron , then the stationary mag fld will deflect the electron , but if the mag fld is moving , it will acelerate an elctron from rest . Its just a point of vu , if you are a stationary electron , or a mag fld , you see the other moving .
Plywood glue is cured by the "other" thing in an RF fld . The electrostatic force on wood fibers will rub them , heating them .
Rambling along .... HF MIG wire will stop , arc distance increases and noise goes down and power to weld goes down BIG ! You can MIG if the wire is not large diameter and almost touching the work . The reasons : MIG only has a low voltage , many arcs are 10 to 20 volts .
Stick welders can make a welding 'arc" anywhere in 5 to 25 volts for the amps is mantained , the voltage increases to maintain the amps. But MIG stops dead , for its voltage is clamped to 24 vdc . So pull the wire away a bit too much and you STOP welding ! Your MIG box would work better if it had a sophisticated elect control to speed up wire , for operator errors . You would maintain the power at the work . This is why i recommend to novices : Always speed up the wire too fast , then reduce if it dont weld . Too slow speed will baffle many ppl . Since MIG has a too high resistance in the small wire , always use the largest wire . I use .035 on ALL steel . ? Its intuitive to start on .030" steel with a small wire , it may be a "match" . It just complicates learning , covers up problems . But the complainst will be , its too fast to burn thru ! Yes but isnt that the main complaint always ?
Basics of welding : thin edges will need to burned back and form a round bulb edge before you can begin to build up and fill a hole , so burn the bulb quick and move fast , dont linger . The book says gring a perfect fit ???
OK , do it .
But ill burn a bulb and do a 2nd pass and its over in seconds ! Since you have CO2 coverage , you can do many passes over a MIG weld and get strong bond .
MIG is a quieter arc , very close , sometimes wire will touch and push ya a little , its a lower ,, blue arc . If you are too far away , quieter ,, whiter , brighter , you cant weld here .
Notice the split rollers on 151T 220vac HF MIG ? Better idea , less force to grab wire . i dont like small diameter rollers . Im workin on a wire feed device , no rollers , 3 cams push 3 arms , wire grippers can be very fault tolerant ! They dont bite the wire , but they dont need adjust force !