[Brian O.]

Hello,

First time poster here in the forum so go easy on me.

Recently got back into some Aluminum TIG welding on a project for my diesel pickup. I'm well versed with carbon steel and stainless welding using stick/MIG and TIG so aluminum is still a mystery for me. I decided to hone my skills by laying beads in the flat position on a 1/4" thick scrap flat I have lying around. I got very comfortable doing this after about half a day and decided to move into Fillet welds. This is where everything weld to crap. I cannot for the life of me figure out the trick to starting the fillet weld bead without a multitude of issues. Black soot, contamination, filler rod balling up etc. Even if I'm successful in bridging the two pieces with a decent tack weld, I cannot carry the bead the length of the joint. I've messed around with amperage, A/C balance, frequency, torch angle etc. all with the realm that my research said should work.

Here are my settings that I've tried that I've settled on:

Amperage: 180 (foot pedal modulated)
A/C balance: 70% EN
A/C Freq: 70hZ
Tungsten: 3/32" Ceriated (Sharp)
Torch: WP-17 Air Cooled
Cup: #7 Gas Lens
Argon flowrate: 15-20 CFH
Filler: 4043
Base metal: 6061-T6

I look forward to all of your input!

Brian

[exnailpounder]

Rest assured that filets are the absolute hardest weld to do in aluminum so you are not alone. You state that you have experience in tig on mild. You do not have experience on aluminum and it's different and you're realizing that now. You will get black soot at the start of a filet because your gas swirls around the backside of the work and draws in air...clamp something on the back to trap gas. Your rod balls up because it's either too thin for your amperage or you have a bad torch angle and you're pointing the heat at the wire. My best advice is when you start your weld, mash down the pedal with more amps than you need to get an instant puddle and then finesse your pedal as you move the puddle forward and fill. Your arc will wander like hell unless you keep a VERY short arc length and a steep torch angle. Don't be afraid to extend your tungsten out around 5/8" so you can get it into the corner. That should stabilize your arc a little. I said it should..doesn't mean it will.

[Poland308]

Your arc will wander like hell unless you keep a VERY short arc length and a steep torch angle. Don't be afraid to extend your tungsten out around 5/8" so you can get it into the corner.

Arc length and torch angle are key. Your problems with the filler wire balling up is common to torch angle issues.

[Otto Nobedder]

Brian,

Arc length is the toughest thing to master in a TIG aluminum fillet. You must get your tungsten in very close to establish the puddle anywhere close to the root. Then, when your edges are melted and a dip of the rod will tie the pieces together at the root, the added rod will swell instantly and you must pull the tungsten back. Then advance to the front of the puddle stabbing it in there again, so the puddle itself moves forward before you dip again. Then, lather, rinse, and repeat.

Steve S

[BigD]

One suggestion from a semi newb is to not sharpen your electrode. Or more precisely, not to put a sharp taper on it. You can put a point on it but keep the angle shallow, 45 degrees or flatter. It feels like the sharper and pointier the tip, the more you'll be able to pinpoint the arc, like sharpening a pencil. But the reality is the opposite. The more blunt the tip, the narrower the arc and the easier you will be able to focus it into the root.

Another one is to bias the arc and the filler into the flat piece not the vertical. The thinner the material, the more critical this becomes, especially as you move on and heat soak the piece (prepare to pull a lot of pedal out as you go).

Next, get in there tight, straight and hard. I found it very easy to lie to myself with the T fillet joint because it's so hard to get in position to see without lengthening the arc or tilting the torch. And if you camp out waiting for things to puddle, you will get impatient, add filler before it's time, create a fat bead start, heat soak the piece and from there it's a s**t show. You'll be fighting it trying to get the blob to neck down on an overheated piece, all while getting pissed off and having too much arc length/torch angle as you try to move around the fat fillet and that will make your filler ball and blob. Jack your amperage higher than you think you need, you can always back off. Get it to puddle and fill it quickly. Then you can back off if needed and motor along. Overheat is especially an easy trap to fall for because as you get frustrated with the overheating, you instinctively back off on the heat and you just make it worse. Counter-intuitively, to prevent overheat, you have to jam more amps more quickly.

Again, take it from another newb who was fighting with this same thing not long ago - your torch angle and arc length are too much, even if you think it's not. Part of the trick though is as the fillet starts, you need to pull back just enough so the arc length remains the same but the puddle doesn't reach the tungsten.

When I was battling the same demons, I wanted to strangle Jody as I would go back to watch his T joint videos, making it look like a 2nd Grader could do it on the first try.

[Brian O.]

When I was battling the same demons, I wanted to strangle Jody as I would go back to watch his T joint videos, making it look like a 2nd Grader could do it on the first try.

Amen to that! He certainly makes it look deceivingly easy. Jody was the reason I decided to get more into TIG welding than I had previously. Glad to know my issues just have to do with seat time. I had been reading too that my amperage for that thickness of material was way too low and that a fillet weld on aluminum needs all the amperage you can throw at it or else you'll be exactly where I am right now. I think my welder will max out between 200-210A...not entirely sure. Things I intend to work on regardless are my torch angle and arc length the next time I'm under the hood.

I've also heard from other forums that it would be wise to turn my A/C Freq up to the 150hZ+ zone so as to better focus the arc into the crotch of the joint. I understand that doing so can have a cooling affect on the arc, but some guys swear by that methodology so I figure, why not give that a try? I used to work for a company that designed and built aluminum structures for stages and all their welders made a distinct high pitched hum as if they had their A/C Freq up past 250Hz.

My machine, an AHP AlphaTIG 200x also has the ability to do pulsed TIG welding. Would there be any benefit to running a high frequency pulse in this application or is it best to keep that out of the equation until I can run fillet beads without?

Thanks,
B

[Oscar]

Pulse TIG welding when you're already supposed to be at the maximum your machine puts out will only further reduce the heat input, which is not something you'd likely want to do. Now of you had say 350A on tap, then I could maybe see a very high amperage pulse helping straightening out the arc cone, followed by a lower amperage base-current to not over-saturate the part too soon, where you thereby end up with an "average" current suitable for the 0.250" thickness. There's obviously lots of factors, but the common denominator for aluminum TIG is that you need a lot of current because you usually want to establish the puddle quickly in the beginning so as to not over-saturate it to the point where near the end of your bead, you have a 1" wide puddle drooping down into the base metal.