DC TIG for Aluminum

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This topic came up some time ago also, but I found something in a welding manual that grabbed my attention.  In the book Modern Welding (2004 edition), the authors state that AC and DCEP will break up the oxides on the metal.  They do point out that DCEN will not clean the metal.  They also point out that AC is usually used.  Anybody ever used DCEP for aluminum?  How did it work for you?Patrick
Reply:Works great, but you have to use helium.  The arc is harder to start but you will get an instant puddle even on thick aluminum.  It leaves a gray soot on the weld but it comes off easily.
Reply:works good  for meChuckASME Pressure Vessel welder
Reply:I did DCEN GTA with helium fillet welds of plate bases on aluminum light poles.  The pole was about 8" diameter and 3/8" thick, and the plate was 3/4" thick.  The power supply was maxed out at 300 amps, the torch was a HW-20 water cooled, the tungsten was 1/8" diameter, and the filler was 1/8" diameter 5356.  The welding was quite easy, plenty of heat and weld penetration.  I had to push a lot of rod into the puddle with each dip, in order to get about a 3/8" fillet.  The water cooler had some trouble keeping up and the torch power lead hose blew out a couple of times.I am interested if anyone has tried DCEN of thinner aluminum with Argon.  It seems like it should work ok if the material is absolutely clean.
Reply:I would like to rey it but with the prices of argon from the place where I exchange tanks, I shudder to think what helium might cost.
Reply:From everything I have read here and in other spots, the aluminum has to be clean to run DC TIG.  Funny thing to me is, doesn't the metal have to be cleaned for AC TIG on aluminum too?  Just an observation from an innocent bystander.Patrick
Reply:Originally Posted by pulserI am interested if anyone has tried DCEN of thinner aluminum with Argon.  It seems like it should work ok if the material is absolutely clean.
Reply:i have run dc tig on alum with argon and it will work but you have to clean the ***** out of it firstChuckASME Pressure Vessel welder
Reply:Hello,To derive the benefits of DC welding aluminum you must use 100% Helium. You can wrestle with Argon but the results are counter productive. You have to sometimes spend more on the gas to speed up the process and achieve the desired result.
Reply:Tried it today, for a gaff. DCEN, Argon, 3/32 tungsten, amps between 70-135. I only made molten beer cans. I added tons of filler rod, and no negative side affects; it forms an arc easily, and the arc is good. But the actual bonding/ fusion is UGLY. Ran the gas higher, but no avail. Still only got ugly puddles of molten sludge. I could not see much negative to the weld, other than it would not do anything I wanted. It acted kind of BLAH. I tried on 3/16 and 1/4". It was used Coors after a few seconds, and the two sides of the weld would not pull together at all. AC tig is MUCH better suited to this stuff!
Reply:DC TIG with helium and straight polarity is used on thick alum .AC is easer but some times you don't have an AC machine and a tank of helium is cheaper than buying a new welder and it works good on 1/8 and up ,works OK on 14ga but kinda hard to hold and arc and once you start you got to go or you will burn throughChuckASME Pressure Vessel welder