[Chrispy350]

Hello folks.
I'm having difficulty getting reliable tacks into fabricated aluminum parts (.05 thick, 3003 H14).

When I tack up 2 flat pieces of 6x6 practice sheets, no problem, even with a small gap. I can lay down tacks quite reliably. I'm trying to use minimal heat, so I've switched to 1/16 2% lanthinated tungsten, 1/16 4043 filler running an Everlast 200 at around 60a.
When I tack the test sheets, I'm running 3/4 pedal, crossing over the seam or circling around it, then dabbing to create a puddle -- no problem.
When I try to do this with 2 halves of a motorcycle tank, the edges burn away quickly and/or the filler rod refuses to melt cleanly, and instead becomes a ball of goo (usually telling me not enough heat). Same material, same fitment, same settings.

Any hints on how to navigate this fine line between too much and too little heat? I've destroyed some pieces it took hours and hours to make, too many times now. There must be some technique I'm not picking up on. Could this be because the test pieces are laying flat on the table and the other pieces have no backing?

Would appreciate any advice - thanks in advance -- Chris

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[Poland308]

Can you put a heat sink on the back side?

[Chrispy350]

I probably can, like a heavy strip of copper.
Think that will help?

[cj737]

You also need to be very mindful of the heat accumulating in the thin sheet metal as you go along tacking. Especially with thin aluminum.

Keep a bucket of ice water handy and a rag. Tack once or twice that plop the ice cold wet rag on the tank. That will chill it rather quickly. Wipe dry, proceed. It will also help prevent the major distortion that occurs with heating thin metal.

[Olivero]

Motorcycle tanks?

I love motorcycles.

Anyways, not getting off subject here..... I have a ZX-6R.

Okay ENOUGH!

SO! What I'm seeing here is you are heating it too much and don't have your filler in place before you go to lay the tack.

Aluminum is notorious, absolutely freaking notorious for doing this, what you can zip up fusion style with steel, you cannot with aluminum, it will not fusion weld very well as it does exactly what you are seeing exactly when you can't have it do it.

So from having fabricated a lot of aluminum I can tell you something that might help.

For one, for every tack you lay down, the aluminum gets hotter, when I'm doing 3/16 or 1/4" aluminum, it's like a nightmare the first couple of tacks because it takes FOREVER to get it hot enough, but once you've cooked it a little, it all becomes much easier and by easier I mean it gets hot enough a lot faster.

So when you start out, you go , bzzzzzz, dab, done, then the next one is bzzzzz, dab, done. Then you go for the 3rd one and you go bzzzzz, it warps, you dab, it's too late, it's done. but you should've only done bzz and then dabbed and you would've been golden.

It's a bit of a PIA to tack aluminum but you can either lay down the filler already where you want the tack as it will help absorb the heat or just treat each tack like a completely new one rather than wash, lather, rinse, repeat type welding, expecting each tack to take the same amount of heat and time.

What I've also done is just put a dab of material on one side of the "weld" so say, the right piece where you want the tack to be, then a lot of times it will allow you to just fuse it over into the opposite piece, but that's normally when putting stuff together, but it's an idea.

Hopefully that made sense.

[Chrispy350]

Thanks so much, folks.
I will try both suggestions.
I have no problems getting a puddle going and pushing it along with good penetration.
It's just that one little dab that's getting me at the moment....
Thanks again.

[cj737]

The other thing I see, don't aim the arc at the joint. Start on one side and them wick across with filler.

[Arno]

In addition to the points above, metal composition may also be getting in your way.

Your test flat sheet alu usually is very plain 99.9% pure without any additional elements. That makes it react quite predictably and benign.

Alu that needs to be worked/stamped/pressed/extruded like your (original?) fuel tank usually gets elements added like silicone, manganese, etc. which can influence how it flows a lot. (up to making it pretty much un-weldable in the 7xxx type alloys)

Of course on an old(er) tank you also have the joy of dirt/grime/oils boiling out of the material as you heat it and messing up your puddle and making it flow together badly.

Bye, Arno.

[Chrispy350]

Super, Arno - thanks.
Good thoughts.
I realize that the precut coupons I picked up are also .06 and the tank material is .05.
But the tank metal is all newly formed, etc. Still, your point is well-taken.

I've landed on another method that oddly seems to be working: bury the tungsten inside the cup about 1/8", turn the amps up full (in my case 130), put the cup directly over the seam and give it a half-second full-blast. Seems to do an acceptable job of fusion tacking if there is zero gap. Still experimenting, and would rather make a tack that allows for some space, to ease the tension on the seam.

Thanks - great forum here....

Chris

[cj737]

The downside to your approach is creating too long an arc. 1/8" is pretty far away.

But this is also creating another side benefit; preflow. Any time you need to stabilize the arc with low amps, having at least 1 second of preflow of argon helps evacuate the oxygen in the weld area and initiate the arc at a much lower amperage. I run 2 seconds on thin stainless, ally and especially Ti.

I'd keep the tungsten just proud of the cup personally, so I could see better. Then super tight with no filler when I tack.

[Oscar]

running an Everlast 200 at around 60a.
When I tack the test sheets, I'm running 3/4 pedal, crossing over the seam or circling around it, then dabbing to create a puddle -- no problem.
When I try to do this with 2 halves of a motorcycle tank, the edges burn away quickly and/or the filler rod refuses to melt cleanly, and instead becomes a ball of goo (usually telling me not enough heat). Same material, same fitment, same settings.

My best results/advice for tacking aluminum are: make 100% sure the edges are touching with no gaps. Very high amperage for very little time - difficult to do manually so a spot timer works GREAT for this. Does your machine have a spot timer that you can use with a momentary on/off switch? If so, it would have been your best friend. On 0.050" material, I would have started experimenting with something like 100-150A, 0.1-0.2sec on time, 150-200Hz AC Freq, 75-80% Electrode Negative AC Balance, about 2mm arc length. Again, these would be my starting points. I would fine tuned based on what I saw from the very first attempt.


What you see below is me investigating tacking on 1/16" outside corners. That was with me using the foot-pedal, which is not all that fast when you have to let-up manually. Those tacks, even letting off as fast as I could, are probably around 0.3-0.4sec each. Using a spot timer which can react much faster, and with the higher amperages I mentioned, I bet those tacks could have been even smaller.

[Chrispy350]

SUPER helpful, Oscar - thanks.
When you do those tacks, are you moving the tungsten at all or just keeping stationary?
I don't think I have that function on the Everlast, put perhaps I can cheat it with the pulse settings.

[Oscar]

Stationary - these are too fast to do anything but.

[VA-Sawyer]

Oscar,

That is exactly the kind of useful information that I was talking about in the other thread. The Pulsar strikes again!

[Chrispy350]

Wow, some good progress.
Most helpful seemed to be to turn the frequency up (200hz or so) and being diligent about keeping the tip of the tungsten as close as possible.
Thanks so much folks, very happy to be able to keep going.....
Chris