Framebuilders - Tig Welder

Hi everyone i am new to the forum and am in the process of building a gold rush recumbent bike , made of aluminum .
I am a mechanic by trade and owne my own business 43 yrs. now and i have always used snapon tools , I had the chance to trade my snapon mig welder in that gave me good service for 15 yrs. for a new snapon welder that had mig ,tig and a spool gun . when i opened the boxes i found that the tig would weld brass , steel, stainless steel , crome-moly ,and all the other metals but not aluminum . the heat settings range from 50 amps all the way up to 190 amps , it is reverce polarity like most tig welders and i have tungsten electrodes ,I just don't understand why it won't weld aluminum when it will weld all the other metals .
Can anyone help me on the situation ?
thank you and i really enjoy reading the threads you guys have.

Marion

It's been awhile, but does it have alternating current or just direct current? If I remember correctly you can only TIG weld aluminum with an AC welder. Hope that helps.

It needs alternating current, and the reason for that is that it needs to blow off the oxide that forms instantly over raw aluminum. I did wonder at one time if there wasn't a way to DC weld aluminum, because frankly everything is possible with welding, and was probably typical at some point. Recently I came across infor that said it was possible to DC weld aluminum, but whatever the trick was it require something other than Argon to do it. So for me I wouldn't want to go a whole other rental. It is also possible to gas weld aluminum if you have that gear, get the right flux from Tinmantech, though proceed with caution and be sure you can do what you want with the alloys you want. Often one needs to heat treat the aluminum frame after welding which sounds like a pain. I had a friend who welded aluminum and got the frames heat treated in exchange for more Al welding.

Also, Al likes the higher end welders that have stuff like square wave, etc... because they give better efficiency and aluminum needs a lot of power to get the job done. Not much of a concern at our thicknesses.

Thanks everyone , I got the manual out read about it and it is a dc welder so i guess i got a tig welder that can't weld aluminum except for the spool gun.
So i guess i'll can that project and go to the next one.

THANKS AGAIN
Pottsy