I'm going to play the part of the dummy, so bear with me.
80 Hz - so you are using AC, slight emphasis on the EN polarity
Ceriated tungsten - I assume you’ve used this electrode before with acceptable results?
Consider the following:
1) Have you tried using EWZr with a balled end with a balanced AC wave?
2) Have you considered using DCEN with helium shielding gas (w/ thoriated tungsten) Just a thought, not high on my list of recommendations.
3) As mentioned by TJ, have you tried a larger gas nozzle with a gas lens to improve shielding gas coverage?
4) Did you degrease the aluminum before using the rasp and wire brush to remove the surface oxides?
5) Have you considered following the acetone degreasing with 90% Isopropyl alcohol after using the rasp and wire brushing the joint?
6) Have you cleaned your wire brush and rasp with alcohol before using them?
7) Are you handling the filler rod with your bare hands or are you wearing clean gloves?
Best regards - Al
"There are some good posts on here about making homemade trailers out of sintered copper and such."....taken out of context the way search engines like to do, this sentence is going to give a big ol mindf*ck to some hobby welder searching for tips on building a trailer..the kind with axles that is
Back on topic... To fschweighardt, its a bandsaw cut [no coolant/lube] then an acetone wipe, then vixen filing down to bright metal. This procedure worked fine for the outside corner joints done on the same assembly with the same metal.
To Tommyjoking, big cups are on order tomorrow. Just last week I did some 3/16"flat to 3/16" tube repairs on a fishing frame. It presented many of the challenges present in AL GTAW. Dirty base metal, hydrated oxide, rewelding same plates back on so I needed to clean out the old weld metal. Ended up doing two passes, with a slight weave on the second pass, and no problems with shielding or dirty puddle. Ultimately I think it was a combination of a weird joint and fatigue/shaky hands. I got the first one done this afternoon, and I'm headed out tonight to finish the other.
To 803056, playing the part of the dummy...HA!..I've read your posts sir...yes using AC on a Lincoln Invertec V205-T. The ceriated has always worked in the past, and even at different joints on the same assembly no problems. But I've never been fully satisfied with their performance. I'm running a 1/8" tungsten at 80Hz, 53% EN, 190 amps. If I weld on a freshly ground tungsten, even with a relatively blunt point, the tip of the tungsten melts in weird ways and forms little bumps. If the Elephant Man was a tungsten, that's what it looks like. So I grind a 140 degreeish point, crank the balance down to 35%, and blast it with the footpedal until it melts into a ball, then turn the balance back up and start welding. At 190 amps, even dropping the balance down to 50% will cause the ball to sag and the arc gets a bluish tinge. Tungsten inclusions?? Are Zirconiated tungstens suitable for this machine? Clean gloves with nitrile exam gloves underneath, so no contamination there. I know the alcohol after the file and brush is recommended, but I'm lazy. Maybe it's starting to bite me in the ass.
By aevald 
Date 03-16-2012 02:44
Edited 03-16-2012 04:35
Hello devo, with the cleaning regimen that you are going through I believe that I might back off on the balance being towards the reverse polarity side so much. This should also help to preserve the tungsten a bit better. I have experienced puddle contamination on some things just because of excessive penetration settings of the AC balance, too much EN. Additionally, I don't believe that you need to do any sort of "balling" on your tungsten, particularly considering that you are using that nice Invertec. Just about all of the newer inverter type machines no longer require or suggest balling of the tungsten, nor do they recommend using pure tungsten at all ( I realize that you are not, but others reading this might not realize that). Instead grind your tungsten to a point and then blunt off the tip a bit, 1/16" inch or so. Your hertz adjustment will deal with focusing the arc, and typically provide the necessary energy to yield a nice bead. Tommy is so right about shielding, I know a lot of people don't pay a lot of attention to shielding on aluminum so much as other more reactive metals, yet, if you don't, you could end up with some of the issues you have been seeing. I don't know if backing any of these welds is a possibility, yet if it is, simply using some stainless steel or copper clamped strategically might help to prevent contamination that might be drawn in from the backside of the joint or possibly help to contain the shielding gas around the starts or terminations of a particular weld bead. I will sometimes see contamination upon exiting a bead at an edge because the shielding gas doesn't have any way to completely cover the molten puddle as it "wraps" a corner or an edge. Having a backing of some sort aids with containment and prevents contamination. If you are already well aware of these things just simply ignore my ramblings. Good luck and best regards, Allan
The parameters on your sketch are perfect.
There is no value in increased frequency on material that thick but it doesn't hurt either :)
No need to ball your electrode... No need for a change to zirconium... This will only lower your current carrying capacity.
Now... Go get a piece of scrap and tune your machine/torch in as you obviously have a gas/contamination issue.
Take off that stupid gas lens and try a standard cup... See if that doesn't solve your issue right off the bat. People think gas Lenses are some silver bullet that will make all welds x-ray quality... Nope....... Those fine screens when disturbed by irratic arc starts commonly found with AC welding can get chewed up and cause worse gas coverage than standard cup collet combinations..
Secondary Argon Gas trailers for aluminum? don't wast a single moment on this thought, not for what your doing.
Thanks for your replies all...Just a couple more questions for you Lawrence,
I've tried welding with a sharp tungsten like you [and so many others] have suggested, but I still end up with the Elephant Man tungsten. Maybe my grinding wheel is contaminating the tungsten? You mentioned the gas lens screen getting disturbed by erratic arc starts, how about getting disturbed when my tired caffeinated hands crash the damn wire into the tungsten? I did scrounge up some #10 cups for the standard collet, but it seems that the increased stickout of the tungsten = increased resistance heating = higher EN% to keep the tungsten cool = less cleaning action. Maybe I just need to experiment more. I am using short pieces of tungsten, so short they don't even stick out past the top of the collet. Could this be trouble? I'm using a water cooled torch, but maybe I need longer tungstens.
One other possibility, it was around 60 deg. ambient air temp in the shop, kinda humid too. Maybe a touch of preheat with a hot air gun to start things off?
Ultimately my fatigue and caffeine intake had as much to do with it as anything. I noticed I was holding too long of an arc for fear of crashing the tungsten..again.
No preheat
A longer tungsten is always a better heat sink
Remember a traditional transformer/rectifier power supply set to "10" Max Pen will provide 68% EN... So keep that in mind when dialing in your inverter... Keep it between 50 and 55% for most work
No long slim tapers on your tips... Keep it a radical grind with a blunt at the end... This way when the end begins to deform it will not make a large droplet at the end of your electode
*ANY* contamination is reason to stop and clean... Remember that aluminum goes up tungsten like a straw so you need to clean the inch above the tip as well... Any junk will render the super powers of your inverter useless.
Thanks for the advice Lawrence...I am guilty of not cleaning the tungsten all the way up after a crash. I learned long ago it's better to stab the puddle with the tungsten than to hit the tungsten with the filler. I've got a lovely collection of broken off bits of tungsten, wrapped in a sparkly aluminum sheath. I need to be as diligent with my tungsten cleaning as I am with my base metal cleaning. I'll be asking for your input more often, as I am teaching a welding class a couple nights a week at a local technical college. Just basic SMAW for students not in the welding degree program. I had a student ask me about cleaning aluminum for welding, and I told him, "pretend your grandma wants a bowl of soup, and the only spoon you have is stuck in a pile of bloody dog sh*t...how clean are you going to get it?" He got the point...
By Tommyjoking 
Date 03-16-2012 17:59
Edited 03-16-2012 18:22
Sorry Lawrence/Devo but I got a bit off topic referring to welding stainless and steels. Just the gas coverage issue in general. But if you fix a lot of kitchen equipment you will be running into more SS then anything else, having those things in your toolkit is very helpful. That is what I meant. For the issue at hand a slightly bigger cup and maybe adjustment of the gas flow should fix it...it sure sounds as if the metal is well prepped.
Devo is your tungsten extended beyond the rim of the cup? It should just a bit. Ceriated tungsten...there is no need to ball or sharpen it with AC welding. I put in snapped off blunt pieces in and the ceriated takes care of itself. It will form a nice slightly rounded end and keep it at the right size vs amperage.
