problem tig welding aluminum

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I've been off the tools for about ten years now and behind the desk full time. I had to dust off the cobwebs and TIG some aluminum today. I ran across the weirdest problem. While welding, the arc became wildly unstable and the tungsten started spitting and actually eroded back up into the ceramic cup.I'm using an old Lincoln 250/250 machine and I was using AC, hi-freq. The base metal was 3003 plate as was the filler. The gas was a custom mix that is specifically for aluminum. I had a thick chunk of scrap aluminum plate on the bench (to cover the mild steel benchtop and the project pieces were clean. It felt like the power supply was wonky and the weld puddle was uncontrollable.Any thoughts??Thermal Arc Fabricator 2101970 Lincoln RedfaceMiller 150 STLStill need a Syncrowave and a plasma and a milling machine and a lathe and a bigger shop and a....
Reply:gas flow is good? this may sound obvious, but are you sure you have tungsten in there? A piece of stainless filler rod mistaken for tungsten will act just like this. It's a great trick to play on those that pi$$ ya off. Since ya say the foot pedal was acting weird, can you bypass it with a torch switch to take out one variable?
Reply:how many amps and what size tungsten?
Reply:thanks guys - yes, gas flow was excellent. Not sure about the amps. This machine has a 3 range tap, I was on the third tap with pedal controlling the amps within that range. I'd imagine I was in the 200 amp range. Was using 3/32, pure tung (brand new) prepped with a ball end using copper and DC+. The custom gas as mentioned is from our LWS - its called Blueshield 1. Not sure what the actual blend is.Now I haven't done tons of alum TIG in my career, but I've done a fair share without problems and never had this happenLast edited by Canoe2fish; 08-19-2012 at 07:35 AM.Thermal Arc Fabricator 2101970 Lincoln RedfaceMiller 150 STLStill need a Syncrowave and a plasma and a milling machine and a lathe and a bigger shop and a....
Reply:Don't use pure! Sent from my Galaxy Nexus using Tapatalk 2Miller: 200dx, Bobcat 225, Passport, Powermax 45, Milwaukee: Dry Saw, MagDrill, grinders
Reply:Originally Posted by JohnRDon't use pure! Sent from my Galaxy Nexus using Tapatalk 2
Reply:Are you sure you switched back to AC after pre-balling the tungsten?  DCEP will eat tungsten in a hurry.  For what it's worth, I just let pure tungsten ball itself in the process of welding.  Happens quick enough but I also use red sharpened the same as I'd use on MS & SS.For 200A I'd give some consideration to using 1/8" as it sounds like your 3/32" may be overheating.I'd also find out what the custom Blueshield 1 gas is.  What's wrong with 100% argon for the job?MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Yes pure is generally recc for transformers. There's a few others that you can use that will handle higher amperage. Try welding at 130-150 amps and see if you have the same problems. I believe you may be trying to push too many amps for 3/32. I use 3/32 up to 260 amps on my inverter, but with a transformer machine where the EP/EN is not as adjustable, the extra heat can easily overheat a piece of tungsten. You may need 1/8"
Reply:Well guess duane beat me to it....btw the blueshield 1 is Ar/He mix. not sure of proportions however
Reply:A quick search shows Blueshield 1 to be an argon/helium mix from Air Liquide.  I'm no pro but I'd have to say unless it's absolutely needed (thick material, to get more capability out of a machine, required by weld spec) I'd say it's just a case of spending more $$ than necessary for shielding gas.May be bad gas.  Is it a fresh cylinder?MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Originally Posted by BCTimberwolfWell guess duane beat me to it....btw the blueshield 1 is Ar/He mix. not sure of proportions however
Reply:Originally Posted by Canoe2fish?? I was taught to use pure tung in aluminum unless it's an inverter machine. Is this not correct? I've always used pure and never had this happen. I'm not saying you are wrong, its just what I've always read/been told.What it felt like is as if there's a problem with the machine's power output.
Reply:Originally Posted by Canoe2fish?? I was taught to use pure tung in aluminum unless it's an inverter machine. Is this not correct? I've always used pure and never had this happen. I'm not saying you are wrong, its just what I've always read/been told.What it felt like is as if there's a problem with the machine's power output.
Reply:thanks for the suggestions everyone - I never considered that 3/32 was too light for the amps. I'm out of touch with what we keep in stock out in the shop, so I grabbed the largest dia. tungs in the kit. As for the BS1, I'm not sure why we have it on hand. I didnt have much time and wasnt about to lug a big argon out of the lockup to switch it over. All and all, I suspect that a 1/8" tung and straight argon would have been the right thing to go withcheersThermal Arc Fabricator 2101970 Lincoln RedfaceMiller 150 STLStill need a Syncrowave and a plasma and a milling machine and a lathe and a bigger shop and a....
Reply:............  tungsten started spitting and actually eroded back up into the ceramic cup............Sounds like the polarity was wrong. Were you really set on AC?Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:Argon/CO2 mix will do that too.  Speaking from experience hehTiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Originally Posted by hobohilton............  tungsten started spitting and actually eroded back up into the ceramic cup............Sounds like the polarity was wrong. Were you really set on AC?
Reply:Canoe2fish  Liked your pictures, Mac
Reply:I use only pure tung and pure argon for aluminum.