Tig - Aluminium when using filler-rod ?

I am starting on welding aluminium,and the type of joint is in this way the thickness is mm.1.5 :
_|
so that the two edge have a light in the corner proximity.
I have tried in a lot of ways, but every time when I go on the external corner the edge is melted.
I try also with filler-rod with very bad results.
If the joint has no light and one edge is over the other I can see the puddle of the melted aluminium and I can weld with good results.
Has anybody an answer at my problem ?
Atomino
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What works for me..the very amature welder..is to put both pieces inside a piece of steel "L", clamp securely and then weld. The steel acts as a dam and doesnt let the melted aluminum flow away instead of forming a fillet. Only reason I use steel, is I cant find a big enough piece of copper. Shrug It does require a piece of L steel with a sharp inside corner, but I simply ran a chunk though the milling machine and made sharp inside corners. I welded a couple bars to the pointed side fo the L so when its sitting on the bench, the steel is in a V shape with the open end, up. Made life a hell of a lot easier for me. But then..Im not a welder.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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Tsk,tsk,tsk, Gunner! Real men only use oxy-acet for aluminum, don't you know?
Bob Swinney
wrote:

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On Mon, 22 Aug 2005 08:43:31 -0500, "Robert Swinney"

Thats what Ive heard from those folks who dont own a 300 amp square wave welder.
Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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wrote:

I have a 300-amp TIG, still prefer O/A for thin aluminum. So do the guys that build aluminum racecars, like Kent White and Ron Fournier.
TIG is definitely easier to do, but O/A isn't that hard after a bit of practice.
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Thanks to everyone, I will try to clamp a block of stainless steel inside the corner. Do you think it's same than copper? In this way the light between the sheets is covered from the block. What the maximum size acceptable of the light ? With thickness of mm.1.5 what diameter is better for electrode, 1 mm. or 1.6 ? Pure tungsten(green electrode) is ok ?
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Stainless will be fine -- maybe even better than copper because it won't chill the work as much.
The best fit is one with no gap. Maximum acceptable size just depends on how good you are with TIG and how much grinding you're willing to do.
Pure tungsten will work, but you'll have much better luck with a zirconiated tungsten on thin aluminum. Try both sizes of electrode, see which works best for you with your machine. I'd use 1.6 mm, YMMV.
You *are* using AC, right?
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Hi Don,
The machine is Lincoln Invertec V205-T AC/DC I am using AC with these settings :
- high frequency tig starting - amperage between 30 and 45 amp - square waveform - AC welding frequency 130Hz - AC balance 50% - Argon gas at 10 l/min
Do you think are important other parameters like :
- preflow and postflow - up-slope and down-slope time - starting and finish current - pulse frequency
I have left all these parameters to default value
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Good summary of your situation! Unfortunately, I can't answer your questions but others may be of more help. My welder doesn't have most of those features; it's an old Miller Dialarc HF. That said, I have no doubt at all that I could make the joint you describe with it.
I did find that zirconiated tungstens made a big difference for me on thin aluminum at the current levels you describe. I'm not a pro weldor, just an amateur like you. We need all the help we can get.
I'd suggest making a backing bar, either Gunner's version or mine, made of stainless or mild steel or copper or whatever, and then keep practicing with "training bits" until you get the result you seek. With backing and filler rod, you can bridge about any gap with good weld -- though you'll have some cleanup to do with the grinder.
One more thought: do you know what alloy of aluminum you're working with? Some alloys are difficult or impossible to weld well with TIG. 60xx and 3003 weld very nicely.
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Shouldn't one be using high freq. full time (not just for starting) with aluminum?
Harold
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On Tue, 23 Aug 2005 00:15:16 -0700, "Harold and Susan Vordos"

Yes. Good catch, Harold.
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Here is one of my past posts

--
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they fly by" - Douglas Adams
  Click to see the full signature.
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On Tue, 23 Aug 2005 08:41:03 GMT, Ernie Leimkuhler

Thanks, Ernie! I forgot to mention small filler with thin metal.
Atomino, in addition to the zirconiated tungstens, the other discovery that made a big difference for me was using 1.2 mm (.045") and even 0.9mm (.035") aluminum MIG wire as filler with TIG.
I did not know that the sharpness of the point determined the minimum current at which an arc would start. That may be part of why zirconiated tungstens worked well for me; they tend to hold their shape better in AC service. I found that if I grind it to a sharp point, it will start well and then sort of shape itself according to the current I'm running. If I later want to run lower current, I resharpen the tungsten before starting.
For many years I thought that I, the Idealarc, or both were incapable of running well below 50 amps, oh well. WRONG! I just had failed to get the tungsten and the filler size right.
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wrote:

I found a 1" x 1" x 12" bar of copper to use as backup behind the weld, welding from the outside. I milled a small chamfer on one corner so it doesn't chill the puddle until it's clear thru the aluminum, but it still supports the adjoining aluminum.
For 1.5 mm aluminum, I'd be inclined to use oxy-acetylene. It makes a more ductile weld than TIG does, don't know why.
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Atomino wrote:

They really need to be touching. Use filler, it also cools the weld before it drips away. Try preheating. less current and more patience. Aluminum oxidizes in 15 minutes, so really clean, really soon.
I actually found welding corners easier than other things, since both edges tend to melt at the same rate. Which reminds me, aiming the torch bakc and forth to even the heat.
I'm not a weldor either, but this works for me
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