Jon Elson wrote:
Ignoramus24925 wrote:
I have two long aluminum bars 1/4 by 1 1/4, connected together in a
parallel configuration:


I need to weld them together with TIG and my question is how. Again,
6061, they are 1/4" thick. What filler is best to use and what
amperage. Should I use lanthanated?
You need a very close fit between the parts, clean carefully and clamp
to hold in place. 1/4" thickness is out of the narrow range of my
knowledge. I got some filler wire from the welding store that worked
well, I'll look up what it is. I also got some MIG wire, and was not
able to make that work right at all.
OK, the MIG wire that I couldn't get to work was 5356. The filler rod
from the welding store was ER4043, and worked
much better.

My welding book recommends Zirconated electrodes, but I think newer
practice is to use Lantanated for aluminum, and I think
that is what I used when I did a bunch of frames out of rectangular
tube. For 1/4" aluminum, the book recommends
a 5/32" electrode ground to a very wide point, 200-300 Amps, 1/8" filler
wire, 10 IPM weld speed, a 1/2" cup and
25 cu.Ft./hour gas flow. You can reduce gas consumption with a gas lens.

I have a Lincoln Square Wave TIG 300, but I've never done 1/4" thick
parts. That rectangular tube was about 1/8" wall
thickness. I preheated the work by playing the arc over an area for
about 30 seconds and watched closely for the
very subtle signs that the metal was heating up. One trick was to melt
a little bead of filler metal on the surface of
the workpiece, and when it begins to sag from heat conducted through the
workpiece, you are nearly ready.
Cleaning the work and filler wire with acetone before starting seemed to
help, as well as wire brushing the weld
area.

Jon