Im welding some alum blocks that measure 3"x3"x3" to 2" .250 wall tube. The blocks are 7075 alloy and the tube is 6061, not the problem just figure i would mention. Welding with a Lincoln precision 275 max amps are 340.
So far here is what i have tried:
Straight Argon, 3/32 5053 filler, 1/8 pure tungsten and amps around 260-300 with no luck cant get the puddle to flow.
Then pre-heat in oven to 600 deg for about 3-4hrs gave me 120-150deg before welding all the same on the welder and still not welding tunsten is dancing around a bunch then dropping the ball off the end.
Changed to 1/16 filler and backed off the pedal a bit and moved really slow getting better but still really clumpy.
Changed gas to 75% argon 25% helium and it seemed to make a huge help but i have to still move really slow and tons of 1/16 filler.
Went back to using 3/32 filler and got a new torch wp-18 instead of the 20 still having a bit of a hard time any tips would be cool.

...well other than a recent suggestion of welding with 100%helium and set at DC+ that worked terribly

 

I use a 1/8 zirconiated tungsten with 75% helium and 25% argon..@ 15cfm 3/32 4043 rod gives a nice shiny weld.My machine is Miller 351p..works great on thick aluminum.

 

I could be wrong but I think you're supposed to run that setup on DC-
(I never had much luck with that)

you might want tungsten heavier then 1/8 for that job.

sounds like you need more heat and heavy filler.
What size weld are you looking to put down ?

 

Get some 5/32" Zirconiated tugnsten.

 

Specs call out for 3/16 weld. I have some 5/32 ceriaded (brown) on order but sounds like it may be a while. At first the smaller 1/16 filler seemed to flow better it seemed like the 3/32 filler was cooling the weld too fast and get real lumpy. i will try to get some pics of said welds.

 

Usually brown is Zirconiated, and orange is ceriated, I would take zirconiated for high amp Al welding any day over ceriated.

I say usually because some companies feel the need to be different.

 

If you have a bottle of Helium at hand and a "Y" piece you can mix the Argon and Helium to a 50/50 mix for better results. (2 flow meters help here as well)
Considering your machine is a square wave rather than inverter you won't get the same heat carrying benefit of the Ceriated but it will still be better than the the Zirconiated. If you're already spitting the tungsten across the arc (and I'm not surprised on a square wave machine) you have to increase the tungsten size to 5/32", remember you also need collet and collet holder as well.
I'd be a bit concerned about welding 7075 series Aluminium it generally considered not readily weldable and is prone to cracking.
Regards Andrew from Oz.

 

Go with a helium mix and DCN. The arc will be hard to get started and probably won't be real stable, but you will get some major penetration. Practice on another piece.

 

Also don't forget to preheat your parts before welding. You will get better penetration and better looking welds.

 

it really sounds like you just need to preheat more.. How long are you having to wait for the puddle to form?

 

3-4 hours of preheat should be plenty i'd think.

 

Sorry i did mean that i had ordered 5/32 zirc not ceriated tungsten but im still waiting on it. Im pretty sure once i get it thinks will go easier. I have an oven to preheat the peices but like i said at 600* for 3-4 hours only gets me around 150* As promised heres some pics.


the pieces


the jig


weld with 3/32 filler


weld with 1/16 filler


and another 1/16 filler


finished peice only another 50ish to go. 4 fillet welds couldnt take longer thats all ive got done today but i do let them cool in the jig before take them out.


thanks again everyone, keep the help coming

 

I second the 100% helium DCEN.

 

Make another jig. That way you can get them done twice as fast.

The welds look a bit on the cold side. I think you have to preheat alot more.

BTW: where is your ground hooked up?

 

i go with preheating more (only the block )

 

get an oxy/acetylene torch and go to town on those bad boys.

 

You sure about the 7075 blocks. 7075 is in the welding industry considered a non weldable alloy along with 2024

 

7075 its considered non weldable, but it will weld just fine as long as they are not used for strenght or pressure.

 

x2

 

Use 100% helium and put the machine on DC straight.And sharpen the tungsten like steel.Use 2% 3/32 and you can weld a 1' square block of aluminum without preheating at all.And remember that aluminum loses its heat treat at 600 deg.