Lack of pen in a 1/8 inch 6061 T6 fillet

by mike
(canada)

Hi - we are trying to achieve a class A level of welding qual (AWS D-17.1) .125 and .080 Fillet 6061T6 , in a fillet jig with back up gas @ 3 psi. 3/32 Lanth electrode prepared at approx 22.5 degrees with a small flat on the tip. We are using a Dynasty 350 machine. Settings as follows - D. Sq wave, torch gas approx 15-18, 160 hz, amps 160, Balance 75-80 % EN-EP. Each pc of alum is meticulously cleaned with alchol, and brushed with SS wire and cleaned again. Set on a clean hot plate to remove mositure @ approx 150-200 F. The weld profile is outstanding (4043 1/16 filler) but a lack of fusion at the root is obvious when joint is exposed to RT (xray). 100% argon should do the trick but will also try 50/50 AR/Hel for our next run. The travel speed is quite slow to ensure a "keyhole" is seen prior to moving along the 4 inch test pc. Could you describe a suitable recipe for this machine or other suitable suggestions so that our team of welding technicians can over come this problematic issue. I feel that everything is in place from a welding technique point of view we are missing something when it comes to specific alloy knowledge and machine setting. We have no difficultly with other austentic or super alloys. I have also on my welding table 5086. This is also an acceptable alloy in which we can qualify in case you may have some specific info for this non-ferrous alloy also. Thank-you in advance. We need to get this right and soon.

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Mike,

this is right up my alley.
I fought with D17.1 for many years.

from my experience, there are 3 main things that prevent complete fusion in the root of a tee joint on aluminum.

no backing gas...argon shielding on the back side of the upper member helps the puddle wet in the corner.

too much chill... using a stainless spacer on the back side of the upper and lower member helps to retard heat dissipation from a heavy fixture.

too much torch gas...this one is common.
a tee joint will trap argon gas better than a butt and less gas will work. you will probably notice an immediate difference in the sound and volume of the arc just by reducing the flow of torch gas to where it is just enough. ( 12-15 using a #7 cup)

as far as settings go, your settings sound pretty good...I would recommend ac balance set to 70%en, ac freq set to 120,
use either advanced square or triangle wave form.
amplitude set to default or equal amps on ep and en.

the helium addition will make a big difference but you should be able to do ok with argon.

you can email me directly through the contact button on the home page