[mmprestine]

New here and need some help. I have been messing with Tig for the last year and feel very comfortable welding all sorts of materials. The one that I have been working with lately and is driving me nuts is welding a fillet around aluminum tube ( 1", 0.065 wall ) to a 1.25" aluminum plate 2x2 in size. I have tried every combo of tungsten and 3/32 thoriated ground to a rounded end is getting me the closest. Starting on the plate I get a great puddle, while pulsing the peddle I swipe across to the tube adding filler. I can get a pretty good fillet but I still get some burnouts on the tube. If I duplicate the weld with thin plate to thick plate I can get it pretty good but the tube is a pain in my arse. I'd like to see a video of this in action from the pros (Jody).

So here is my actual question - How do you weld thin tube aluminum to thick aluminum plate?

Matt

[noddybrian]

Not something I've done much of - but I recently had to weld a fair amount of 1/16" sheet to 3/8" * 1-1/2" flat bar - I managed to light up & puddle on the edge of the thicker piece - then just flick the arc across briefly in a sort of weave to just catch the 1/16 " - on smaller pieces I've used only sufficient amps for the thinner piece & pre-heated the thicker piece with a torch first - don't know if there is a preferred method as I'm self taught - but it can be done - tube makes it more difficult as you have to be much more aware of torch angle as you go round the joint - if you could improvise a rotating fixture to allow the work to spin while keeping the torch stationary this would help - hopefully someone with more aluminum tube experience will chime in on this.

[AKweldshop]

http://welding-tv.com/2012/04/12/tig-we ... num-parts/

This might be a little help....

[Otto Nobedder]

The advice above is sound.

I'd add, preheat the thick section quite a bit, 400F, maybe, and you'll fight the absorption difference less. A heat-sink on the thin-wall tube can help, as well, of you can rig one up. Several wraps of stripped one-ought welding lead starting an inch above the weld zone, perhaps?

Just some thoughts...

Steve S

[Superiorwelding]

The advice above is sound.

I'd add, preheat the thick section quite a bit, 400F, maybe, and you'll fight the absorption difference less. A heat-sink on the thin-wall tube can help, as well, of you can rig one up. Several wraps of stripped one-ought welding lead starting an inch above the weld zone, perhaps?

Just some thoughts...

Steve S

I have never tried the welding wire trick, will have to keep that in the back of my head. Wrapping it 1" above the weld zone would be like a restricted weld, I am game.
-Jonathan

[Otto Nobedder]

The advice above is sound.

I'd add, preheat the thick section quite a bit, 400F, maybe, and you'll fight the absorption difference less. A heat-sink on the thin-wall tube can help, as well, of you can rig one up. Several wraps of stripped one-ought welding lead starting an inch above the weld zone, perhaps?

Just some thoughts...

Steve S

I have never tried the welding wire trick, will have to keep that in the back of my head. Wrapping it 1" above the weld zone would be like a restricted weld, I am game.
-Jonathan

It's the same theory as the copper block behind a thin sheet. I've never tried it, but in a TIG weld, 1" above, and in a spiral wrap, wouldn't restrict the weld much. Perhaps even higher would work. Just thinking of ways to pull excess heat out of the thin stuff, while keeping the thick stuff hot.

I'll be interested to see what he comes up with and how it works.

Steve S

[MinnesotaDave]

I'm no everyday pro, but the last thick-to-thin I did was 1/16" tube to 3/16" tube and 1/4" plate on the other end.

I started the puddle on the heavy wall, snuck over to the thin, and once joined started moving.

During welding the arc was pointed at the heavy plate only, the heat would wick up the thin wall, starting to keyhole about 1/16" just as I fed rod.

Worked great, but was nerve racking.

With your added thickness - the above suggestions of preheat would be my bet too. Probably would have helped me too.

The wrapping of copper sounds like a great idea

[weldin mike 27]

Another thing you could try is to pad weld the tube up abit first to increase its wall thickness, not sure if its feasable though.

Mick

[Mike]

Welcome to the forum Matt.

[mmprestine]

Guys thanks for the all the responses. I have been playing a bit more but not quite good enough for my real parts. A little more history. I seem to get into everything and make a few bucks off simple build-able things. In this case the parts are for an intake flange to adapt a mikuni style carburetor to a harbor freight predator small engine. The engines are cheap and highly used in many things like, motor-bicycles, gocarts, mini-bikes, etc. I fab and sell intakes and jet kits for them. The little suckers really rip with a few changes. I actually thought about just redesigning the part flanges to include a nipple then weld the tube to the nipple. I have it drawn in solidworks but didn't cnc it out yet as it is more complex. I have several of the originals machined so might just give it a go. I will get some pictures up of where I am at and how it turns out when I give it a shot.

Matt

[steeldr.]

try directing most of the heat on the thickest material,using the shortest arc possible. You can also use 3/32in. thoriated tungsten and grind to a point, this directs the heat in a smaller area. You can also try dcsp ( direct current straight polarity) and thoriated tungsten (2%) ground to a point, and use 100% helium for the shielding gas,aprox. 15-20 cfm.....................hope this helps, good luck!