Mig on aluminum suggestions question..

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Hi all,I am new to welding aluminum with a wire feeder.  I just got a spool gun hooked up to a trailblazer 251nt and it works fine.  I have already begun practicing and adjusting to the idiosyncrasies of how aluminum runs.  I have been running in all positions and was surprised that it would run vertical up.  I had always assumed aluminum had to be done vertical down because I thought it would be too runny, but not so.Since aluminum disperses heat quickly, I noticed that when I start a pass I get a cold lap or poor fusion at the start.  Then a few seconds later, the bead fuses well and I get good penetration and bead appearance.  I got this setup so I can handle aluminum jobs where TIG is not a cost effective solution as it is too slow, like in the case of a repair on an aluminum trailer frame or floor.Should I have my torch handy and pre-heat the aluminum prior to starting to weld in it?  I know that I run into this when I TIG a relatively large piece that is over 1/4" thick.  I find that if I don't pre-heat, I can't get a bead started and it tends to ball up and look crappy.  Does the same hold true for wire feeding aluminum?  At what thickness would pre-heating be recommended?Thanks,Tony
Reply:A bit of minor preheat can help when welding aluminum, sure.Or just do the backstep routine, start the arc/weld an inch or two past where you actually want to start the weld bead, run back to your real starting point, weld.Also pay attention to how you end the weld bead.  Do a backstep at the end of the bead (or use run-off tabs, etc) so that you don't end up with an ending crater.Go grab a copy of the Lincoln document "Aluminum GMAW Welding Guide" (document number C8.100) from the Lincoln website.  www.lincolnelectric.com  You may have to dig or search around a bit, as Lincoln periodically redoes their website and changes where things are.  The best laid schemes ... Gang oft agley ...
Reply:blend some Helium in and your problem will go away.........  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Thanks for the replies and suggestions.  I don't get notifications all the time on the threads I am part of or I would have replied sooner.Tony