TIG welding aluminum - what am I doing wrong?

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Ok here is a test I did this past weekend.  I am trying to find out what I am doing wrong.  The machine is an old Miller Dial Arc (i think thats the model) and I have it on AC current, mid amperage lever position which is like 60 - 140 or so amps I think.  Duty Cycle dial at like 75%, HF start, 4 sec post-purge, 3/32" pure tungsten and 3/32" 2% thoriated tungsten both sharpened to a point.  The aluminum is about 0.080" thick or so I'd guess.  I have ONE good bead out of them all, or at least to me it looks good.  You can tell which one it is.  To get that I think I like puled the pedal with my foot!  It seems like the arc has to be MUCH closer than when doing steel, is this true?  Anyway, I prepped it with a stainless steel hand brush, acetone, and then I start welding.  Here is the pic - excuse the HORRIBLE job...  I am learning.Thanks guys
Reply:Originally Posted by Jon KOk here is a test I did this past weekend.  I am trying to find out what I am doing wrong.  The machine is an old Miller Dial Arc (i think thats the model) and I have it on AC current, mid amperage lever position which is like 60 - 140 or so amps I think.  Duty Cycle dial at like 75%, HF start, 4 sec post-purge, 3/32" pure tungsten and 3/32" 2% thoriated tungsten both sharpened to a point.  The aluminum is about 0.080" thick or so I'd guess.  I have ONE good bead out of them all, or at least to me it looks good.  You can tell which one it is.  To get that I think I like puled the pedal with my foot!  It seems like the arc has to be MUCH closer than when doing steel, is this true?  Anyway, I prepped it with a stainless steel hand brush, acetone, and then I start welding.  Here is the pic - excuse the HORRIBLE job...  I am learning.Thanks guys
Reply:Wow..I tigged aluminum once. First you have to much amps , lower the heat.I notice for aluminum , you need to go FAST. If you don't you will notice bigger puddle and melting through. Just try going faster , and lower heat.
Reply:You need to set the high frequency control to continuous, not start.   Setting it to start turns off the HF after the weld is started.   You need that HF to keep the AC arc going.The 'Duty Cycle' dial you refered to is the fine current control.   If the current range you selected on the range lever was medium, 60-140 amps (I'm too lazy to go out and look at my Dialarc right now to check the numbers) and the fine current dial was set to 75%, then the machine was set to about 120 amps.   For .080" material, try setting to 100 amps (about 50% on the fine current dial, if the numbers you posted were correct) and use the foot pedal to cool the puddle if it gets too hot.   Step down on the pedal to initiate the arc and start the puddle, then let up on it a little as the puddle begins to widen.   At the end of the weld, don't just let up on the pedal all at once, that's how you get a hole at the end.  Let up on it slowly and keep dipping the rod untill the puddle begins to solidify, that will reduce the crater.Also, keep the end of the filler rod in the gas flow during the weld.  Removing the hot end of the filler rod from the gas flow in the middle of the weld contaminates the rod, then when you go to dip the rod again you get a pop, a poof of black and grey smoke, the filler refuses the jump into the puddle, makes a nasty ball at the end of the rod, and the weld goes all to carp.   Along those lines, also work on not crashing the filler rod into the tungsten, or dipping the tungsten into the puddle.   That's probly one of the hardest things about tig welding, managing the whereabouts of both the torch and filler in relation to the puddle and eachother, all at the same time.   Kinda like learning to eat with chopsticks (which I really suck at and would surely starve if I was imprisoned in China and only allowed to eat with chopsticks!).You might need a couple more seconds of post-flow to keep the gas cooling the tungsten untill it's no longer glowing.Anyways, hope that helps get ya started in the right direction.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Its a good start, Think smaller beads to start (less heat).  If you dip the tungsten, stop and re grind.  DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:it seems like its nearly impossible to tig alluminum without a nice shiny ball at the end of the tungstenm, the arc skips around like hell. try that
Reply:I rarely ball my tungsten, I usually just leave it sharp and I never have any problems welding aluminum? I like to party!
Reply:If you have a DIAL ARC you may need a seperate High frequency box.You have to use HF continous on aluminum.You have to use Pure tungsten with a ball formed on it.The black areas of your welds are oxides forming and coming to the surface (limiting the heat input) and then you start applying more heat, which is blocked by the oxides and then the base metal burns thru. You are not doing the wrong thing . it is just that you HAVE TO HAVe HF continous, and a ball on the tungsten.WORLDSGREATISTWELDER is right.Last edited by Donald Branscom; 03-13-2008 at 11:38 AM.
Reply:This Dial Arc (I think is what it is) does have a HF Continuous setting... so I should try that, eh?
Reply:A couple other things to look at:What is distance between the end of the tungsten and the surface of the plate?  Keep the arc length as short as possible, without dipping the tungsten, around 1/16" is reasonable.  Arc power spreads out rapidily as arc lenght increases, and you need all the concentrated arc power you can get with aluminun since it sucks the heat away so fast.You need to hit it hard, get the puddle started, dip you rod in the weld pool, and go.  Don't linger around trying to slowly created a melt, you're heating up the whole plate.The weld pool should melt the filler, not the arc.  Dip the filler in the weld pool.  Tilt the TIG torch at about 20 deg. off vertical and push the puddle out in front of the tungsten slightly to gain access to dip the filler in the pool.
Reply:Thanks Pulser I'll try it - it seems like it didn't want to pool as nice as I am used to on stainless.  I did notice that the arc had to be super short compared to steel.  You also recommend HF Continuous?  I only had it on start!
Reply:yep, with your power supply you need continuous HF for AC because the current goes to zero every 1/2 cycle as polarity swithces electrode - to + the + to -.  As I understand it, the new inverters do not need HF for AC because they switch through zero so fast.I was taught to weld AC aluminum with 2% Th electrodes.  Sharpen the tunsten as you would for steel welding, then ball the tungsten using DCEP on a piece of copper.  Switch to AC and weld.  The 2% Th ball will tend to form a split which screws up what was a nice uniform arc.  In this case, you can stop and heal up the split with DCEP on the copper again.In the old days, pure was always recommended for AC Aluminum, but if you read about the different tungsten alloys you'll see the the melting temperature, ease of arc starting, and arc stability are much improved in the alloys vs pure.  http://www.diamondground.com/index.htmlOh, and keeping the TIG arc as short as possible helps keep the arc precise and concentrated no matter what metal you are welding.  This becomes very critcal as you weld thin metal at low current.Last edited by pulser; 03-13-2008 at 02:52 PM.
Reply:Aluminum transfers heat way more rapidly than any steel, so like the man said, start that puddle and move! You notice how aluminum just kind of collapses like a rotted wood floor when it is too hot? I think I set my top range at 60 for aluminum, but am not sure.  Watch your penetration, and when in doubt, let off the pedal. It is easier to stop and re-start than it is to waste material. And like some other folks said, that nice even ball on your tungsten is important. Personally, I can not weld aluminum with a point on the tungsten. Let me know how those beads turn out. Good welding, pard.
Reply:Sounds like a good thing to try, balled and pointed.  All I have is an AC inverter, but I'll still try it.If you want a ball with an inverter, just set the cleaning to 65%+ and weld for a short time. Stop and reset the cleaning when you have a ball the size you want.This works for me with any color tungsten.David.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:I have started out with a pointed end, but it balls up on it's own anyways, so I ball it first, then weld.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op