Tigging thin steel to thicker help pls..

[Noods]

Hi All..
Can you advise pls in advance.. I've a little project where I'm needing to tig 1.2mm steel sheet to a 3mm box steel section..

I know what's likely to happen.. The edge of the 1.2 burning away! Do I try to get a puddle on the thicker piece and then push it to the thin stock.. Are there better ways? I'm sure there are... Should I protect the thin stock with a piece of copper underneath? Would this help? Do I set the amps up for the thin stock or for the heavier piece.. ? Lots of questions.. Any advice would be very very welcome, before, I make a start..

Muchly many thank you's ..

NöODs X

 

[eSCHEn]

Set your amps for the thick piece and concentrate the arc on it. Get the puddle going on the thick and wash / wet it over slightly to pull into the thin, thereby fusing it. At the same time dab the filler rod in to cool the pool and stop the thin burning back. Move back over to the thick and repeat until done.


Dunno if that's the best way but it's how I do it

 

[brightspark]

I asked this question once before cant u run a bead down the edge of the thin material which would thicken it up and then run a bead across both pieces it works well on stick welding disimlar thicknesses of metal ???

 

[eSCHEn]

Yeah but TIG is slow to begin with. Why do two beads when one will do with just a wee bit of technique?

That extra time is going to pump the heat into the stock and not be a good thing. Especially on the thin stuff.

 

[Paul.]

The trick is to have a tight joint, if its a long joint then plenty of tacks or clamp a bar along it to hold it down, if it lifts while welding you have a problem, then a tight arc with the bias toward the thicker material, and don't be slow adding filler rod, use it to chill the pool, it really is very easy to do,

 

[Screwdriver]

Does it have to be a bead or can you plug weld?

 

[Richard.]

It's not difficult noods especially with those thicknesses as they ain't a million miles apart.
Tacking I would be up to 100amps and adapt the short sharp blast straight on to a nice fitting joint, get the filler straight in then get back off.
Seam welding it I would aim around 70-75 amps and as EsCHen said strike up on the 3mm get fill in the pool and allow it to wet then just weld it normally. Once you've got a pool and fill is going in you will be fine because you have reinforcement there. The problems of burn through are only going to come about if
1) you stop filling
2) your fit up is bad.

 

[Noods]

Richard did you get my text mTe ?

 

[Richard.]

No mTe. Didn't get it.