TIG and thin(ish) aluminum

[Matt@RFR]

Hey guys, I can't believe I've been reading this board for over two years and this is my first question!

I agreed to build a couple tanks for a customer out of .040" 3003 H-14. Round tank with flat ends inset 1/4". Had a few weld bungs, one with a doubler plate.

I've done fillets on .065" material with mainly successful results, so I figured the .040 would be an easy transition...nope. I couldn't keep from dropping through on the fillets (aesthetic application), and the tank ends kept burning away, like I was too hot. Also, my lap welds were pathetic because I couldn't keep the doubler plate's edge from burning away from the puddle. (and I can do very nice lap welds on .065) The seam in the wrapper (butt weld) turned out beautifully.

And since I know you'll ask, here's the parameters I was running:

200DX

15cfh through #7 cup and gas lens

1/16" 2% Lanthanated

.045" 1100 filler

100 amps (for weld bungs)

No pulse

70% balance

150-175 Hz

Any suggestions? I'm no beginner, but I was extremely dissapointed in my results...and I'm sure my customer was also as I told him I couldn't do it.

[Compchassis]

How big of a tank are you building? .040 is pretty thin for any size of tank. Most of the commercially available racing fuel tanks are either .090 or .125.

I have the same problem, I can weld .090 fine, but go any thinner and I start blowing holes in it. Neighbor of mine is a aerospace welder, took him some .050 to weld and he laid a beautiful bead on it and didnt even warp it. Its just practice. Probably going to have to burn up a lot of .040 to get the feel of exactly what it needs.

[VBI]

Matt@RFR,
I am no expert on aluminum welding but I did successfully weld a .039” thick stamped aluminum radiator fill-cap neck to 10 ga. (approx).135” radiator tank top assy. with a little encouragement from my understanding wife.

I wasn’t exactly thrilled with the idea, but as my wife so elegantly reminded me; “isn’t this one of the ($#%^%&) reasons you HAD to buy such an expensive (!#@$%^*) machine in the first place.”

With that in mind, the 10 ga. had a machined thru hole which would accept the filler neck skirt easily. I pressed a round slow taper shaft into the filler neck so as to expand the skirt for a tight interference fit in the thru hole. I also tried to duplicate the joint as closely as possible with some scrap for some experimentation and practice. The weld came out fine using auto-balance, foot pedal and welding positioner-rotator.

Sense then, I have found that with thin aluminum 16 ga. and under, a continuous tight fitting weld joint (no gaps) will help keep the base metal and the weld metal at the same temperature with more consistent heat input and less surprises. Copper chill bars, rings also help when in direct contact with base metal.

Try to simulate the intended weld as best possible with scrap and practice, practice, practice.

Good luck.

[HAWK]

Matt@RFR,

I would widen out the arc by dropping you arc frequency down to 110HZ, experiment with the balance some- if you bring it up to 72-74, then decrease you amperage a few amps- maybe drop the balance to 65-68 and leave the amperage at 100 amps. Maybe a .063" 1100 filler would be a better choice. It is around .020" larger than you base. It will help pull some of the heat away from the base without interfering with your ability to flow it into the joints.

Pulsing can do wonders for you in this application: 40% peak time-25% background amps around 100 PPS.

I know this is pretty much revamping your entire set up. You should see immediate improvement though.

A simpler technique is just switch to the 1/16" filler and drop your arc freq to 110HZ. This may be enough to do it .

Let us know what happens.

[Matt@RFR]

Thanks for the quick responses guys!

VBI, I've used the wedge trick many times, and it works great! Unfortunately, it wasn't an option for this application. However, the tank ends fit extremely well, so that wasn't a problem. The one thing that differs from what I was welding and what you were welding is that drop through on yours would not have been visible... Do you guys even think it's possible to do these fillets without any drop through??

CompChassis, This was a "header tank" for a guy who restores vintage aircraft. The original tank was .032" aluminum, but was brazed, and he wanted TIG welds. All my racecar tanks I build out of .100" 3003. I do agree, though, that it'll take some practice to be able to weld the .040". When I took the job, I made the mistake of kinda assuming that I could do it. Lesson learned!!

Hawk, I left this out of my first post by accident, but I did try .065" filler, and it did help. I didn't try the pulser because, by the time I got that far, I was getting frustrated and decided to hang it up before I REALLY screwed something up! I have a ton of material left over, so I'll definately be messing around with it, and I'll start with your suggested settings. Thanks!

Attached is a VERY rough rendering I through together for you guys. It should give you a better idea of what I was working on.

Thanks guys, I really appreciate it!!

[lramberson]

Hawk, you are the man. The pulse is the key in the thinner material (below .05) You lead me down this road a while back and I am still trying to get it 100 percent. I have even gone to a little book with the settings recommended by the forum for diffrent materials .
Matt just take your time and practice with a little of the material and be patient, I have never had a rougher time than with thin aluminium and I am stiil Learnun with the help of this team...
Good luck & keep us in the loop on your progress. ( I need a Matt .040 chapter in the book)

[eric75]

What if you cheat and make the end caps a little thicker? would that help?
Or add a little more recess to the end cap so your not as close to the edge of the wrapped part? You can always trim it later.

What would happen if you moved the end cap all the way out to make it a corner weld?

Just some suggestions.

I myself have never been able to get a decent fillet weld in AL that thin. Still practicing with .030 butt welds.

[HAWK]

Hawk, you are the man. The pulse is the key in the thinner material (below .05) You lead me down this road a while back and I am still trying to get it 100 percent. I have even gone to a little book with the settings recommended by the forum for diffrent materials .
Matt just take your time and practice with a little of the material and be patient, I have never had a rougher time than with thin aluminium and I am stiil Learnun with the help of this team...
Good luck & keep us in the loop on your progress. ( I need a Matt .040 chapter in the book)

lramberson,

Thanks for the compliment.

Even though pulse is not a must in most applications it lends tremendous stability to the arc when welding thinner material starting at .065" and below. However, there is a point in the lower amperages (10 amps for example) where pulse is not effective because the different between peak and background amperage is negligible.

[lramberson]

Thank Hawk, a lession noted in pulse.
I would like a week with you to formalize some of my misconseptions in lesser learning, I believe you would bring a lot more to the table than was offered to me at the cafateria of knowlage Keep me straight ,and keep up the good work...
Laurence

[HAWK]

Thank Hawk, a lession noted in pulse.
I would like a week with you to formalize some of my misconseptions in lesser learning, I believe you would bring a lot more to the table than was offered to me at the cafateria of knowlage Keep me straight ,and keep up the good work...
Laurence

Laurence,

Email me: [email protected]

I will gladly help you.

[Matt@RFR]

Eric, thanks for the reply! Unfortunately, those are all things that I wanted to do. My customer is extremely concerned with weight (no heavier ends) and wants an exact replica of the original tank (no corner welds for the ends).

Surprisingly, having the ends inset 1/4" didn't present any problems with burning the edge of the wrapper. I figured it would, but the fillet weld ended up being 1/8", if that, so I had plenty of room.

Does anyone have any insight to whether or not I'll be able to have zero drop through on the fillets on the ends? The tanks will be painted, so I can sand off the drop through, but I allways like to have my welds deliverable with no cleanup.

I'll be playing with this when I manage to find some time, and I'll be sure to keep you guys updated. Thanks!

[FM117]

Matt
What kind of aircraft...just wondering?
I have had some luck by wrapping the od of
the tank with a few turns of copper sheet and
holding it on with a screw type hose clamp.
It helped pull the heat out of the outside
sheet....does this make sense? And then
a little touch up by hand with scotch-brite.
Dave P.

[Matt@RFR]

Dave, that makes perfect sense! I think I'll try and find some copper flashing (?) and give it a whirl. Thanks.

I don't know what kind of aircraft it's for. I usually find out what things are for when my customers send me pictures of the installed part. I'll try to remember to find out WHEN I get this tank done!