[fullmetaljitsu]

Hey guys. So i tack weld aluminum and stainless steel aerospace parts that are prepared to be brazed. I find myself having to work with thick and thin parts and sometimes distort the back of thinner metal running too hot on the thicker metal. Any tips on how to tack two different thicknesses without burn through? thanks!

[MarkL]

The obvious is keep the torch more directed on the heavier material and walk it over to the thin. I also tack somewhere other than the edge, like maybe move an inch in from the end. That gives the thin material a little better ability to handle the heat. And if your machine can pulse, that might also help.

[fullmetaljitsu]

good advice thanks. what do you think of having a cold lap of filler on the material that can catch as soon as a puddle is made?

[MarkL]

If you're talking about lay wire to make the tack, that won't work because the filler just balls up and melts away with aluminum. But you do have to use filler to tack with. Even with two pieces that fit perfectly it's tough to tack aluminum without filler. I always use a smaller filler diameter than I would normally weld with because that won't cool the puddle so much. As soon as you have a puddle on the thick piece, put the filler in to get it melted and walk over to the thin piece. Happens pretty quick so be ready to get right off the foot pedal.

[fullmetaljitsu]

ill try the smaller wire! thanks

[Warrenh]

How are you preping your tungsten. For thick to thin I usually use a sharp tungsten. You can direct your heat better.

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[BigD]

Depending on the disparity of the thicknesses, I go beyond just biasing the heat and treat it mentally as not even joining two things but running a bead on the thick piece and the thin one is basically like more filler - I'm not running a puddle on it, only on the thick piece and the puddle is what melts the thin - so the puddle itself barely nips the thin piece and when you add filler it washes over a bit more. Having next to no gap helps a lot but if you do have a gap then again use the filler to build the puddle until it nips the thin. This way I had success joining long runs of 040 to 1/4"

[fullmetaljitsu]

@warrenh I use a sharper tungsten as well.
@bigd thats great advice..i used your technique and it is working well! thank you