Over optimistic welding thin stainless with my Miller Econotig ?

[lchris21]

Hi,
I've been doing a little project which involves some pretty thin (well thin to me!!) stainless. I'm welding some small tubes (1/2" dia) just under 1mm wall thickness to some sheet approx same thickness along the length. I'm struggling with controlling the inevitable burn through and the weld just running away.
Should I be able to do this with my Miller Econotig ?
Not the most spec'd up welder I'll agree with not a lot of bells & whistles, but Ok for my infrequent TIG welding adventures, so I hoped
For those who don't know, its just a basic, select your welding type, dial in the max amps and plant your foot on the pedal to vary it up to max setting
I've got it set to its lowest it'll go, 30amps, but still find it a bit fierce.
I started with a 2.4mm thoriated, but had a go with a 1.6mm lanthanated (the smallest I got at the mo) with the same outcome.
I'm running a size 5 cup, and stick out depending where I'm welding between 3-8mm. Gas set at apprx 12l/pm & 1.6mm filler rod.
I've managed to stick a few bits together, but its not what I would call show piece stuff
Any tips or suggestions, or am I just asking too much of this set ?
Cheers

 

[Robert]

Mine did fine just keep the point sharp and back gas the tube. Fit up is critical also (no gaps) Use 2% thoriated and if you feel that the diameter is too big just bring the angle of the grind back a bit more than usual. Your fit up should be close enough to just fuse the material without filler.
Good luck
Robert

 

[lchris21]

The gaps could be my downfall ? I'm welding the tube laid flat on the plate, and welding along its length, like a real deep fillet, so trying to get the tungsten into the gap is pretty difficult unless I stick it right out

 

[Robert]

That type of weld is about as hard as they get. Could you drill holes in the plate and weld through the holes to the tube. It is called a "rosette weld" but you will still need to purge the pipe with gas. I have welded two pipes side by side by sticking the tungsten way out and laying a filler rod down in the crack and keeping the arc on the filler rod will keep from punching through. Gassing the tubes cannot be left out or they will have a salty look inside and fall apart in a short while. One cannot stress the importance of back gassing on stainless.
Good Luck
Robert

 

[lchris21]

Thanks for the info & tips lads. I'll give them a go

 

[runnach]

Hi Chris, the term rosette welding as describe by Paul, is termed "plug weld" here in UK if you are googling for info on this method. Stick with 1.6 dia (max)tungsten for 1mm metal thickness. 1.6mm filller wire will not help, try to lay your mitts on some 1 or .8mm st/st mig filler wire (spec?).

Purging is a lot of work, is the completed job critical? You could work pedal to give pulse effect, ramp it up, filler in, ramp down, but rapid!!

Cheers........

 

[Normsthename]

The best thing I ever bought for my TIG Plant was a Pedal
It is really useful when welding thin material because you can back the power off etc
Not cheap though
Earlier this year my Nexus TIG Welder broke down, and I had to slum it for a few weeks on a Loaned Kemppi TIG Welder without a Pedal, I really missed it

Andy

 

[Robert]

Yes you should learn to TIG without the pedal but it is hard to do without when you are accustomed to it. Try a thumb control, that also takes some practise to use. For out of position welding one must use what is available or have the wife pressing the pedal while you weld (I have done that). Some welders here just use a on off switch on the torch as a pulsar, I have not mastered that yet.
Good luck
Robert

 

[hotrodder]

With a 30A minimum output pulsing/pedalling isn't going really go to help on stainless less than 1mm thick. Certainly very doable with an econotig but a bit harder than with kit with a lower minimum output and pulse. As said, 1.6mm filler is a big part of the problem. 12Lpm is a lot of gas to push through a #5 ceramic- not going to be the cause of your problems though.

Any reason why you can't put a small 90* fold on the end of the sheet and forgo filler...

 

[lchris21]

Cheers all,
Completed the job today with a bit of messing around. Will bear the thinner filler rod idea in mind for next time.
Was pulsing with my big toe in the end (bloody cold in the garage with no socks on )
Just to build my confidence back I tried a few straight forward test pieces of the flat stuff in a 90deg fillet just to make sure I had'nt forgot how to set up & tig and it came out OK
Was'nt too bothered about purging as its not needed for what I want.
As regards the 90deg fold, thats a good tip for future, but the tube was laying flat on the plate (like a pen on a desk) hence the deep fillet.
Thanks again

 

[Robert]

Glad you have it done.
If you have time and another set of parts --- try putting a short length of 3mm filler rod flat between the plate and tube then with a sharp tungsten pulse it with your foot at about 50A. Keep the current control on panel and use the contractor on remote as a pulsar. Keep on the 3mm rod only and let it flow out with no other filler rod.
Takes practise
Robert