Welding 5052 Thin-Wall Tube to 6061 Plate

[Sparweb]

I'm about to specify welding of 5052 tube ("O" temper") to a plate of 6061-T6, using GTAW and 5356 rod.
I am more comfortable with steel welding, so if any experts here see anything wrong with my plan below, I'd appreciate a quick shout.

More detail about the parts:
Tube: 2" OD x 0.035" wall, 5052-O (WW-T-700/4)
Plate: 0.063" thick, 6061-T6 (QQ-A-250/11)

End of tube to be welded is cut at a 30 degree angle.
The tube is welded to the plate, so the part looks like a "y".
The plate serves as a flange, which mounts the tube to a flat enclosure.

The only difficulty I anticipate is completing the weld inside the 30 degree angle. I think I have seen such joints before, and even my clumsy hands have done 45 degree joints, but here my experience with steel may mislead me. The thickness of the plate (twice the thickness of the tube wall) is not ideal, but is it difficult in Aluminum? The materials don't match, but I don't want to waste time and money to get a full plate in 5052 if it wouldn't improve the part in a practical way.

I am also specifying a liquid-penetrant inspection after welding, but no heat treatment. The loads on the parts are extremely low (this is an air duct) and I expect the only major risks to this part is corrosion from humidity/condensation, which I am addressing by surface coatings ("alodine" chem conversion, prime, paint).

STF

 

[SwinnyGG]

With GTAW, this weld is certainly possible. Operator skill is key- wide beads on thin aluminum are not for beginners, but it can be done.

 

[berkshire]

Your biggest difficulty is going to be the arc bridging the Vee in the throat of the weld , making a wider weld than you would like.
B.E.

You are judged not by what you know, but by what you can do.

 

[tbuelna]

It will be difficult to keep the .063" flange flat. It will want to curl. Would help if you can CNC machine a raised rim on the flange that matches the tube end profile/thickness so you can use a butt weld. If the flange needs to remain flat after welding, a stress relief would help, if possible. While you might assume the loads on this duct weldment might be low, consider that during assembly if there is any weld distortion the duct might be forced into position or deformed by any fasteners when tightened.

 

[Sparweb]

Thanks everyone. I don't mind it when folks look over my shoulder

tbuelna, good point; some distortion should be expected from any asymmetrical joint. In this case, the flange will be fastened to a very thin sheet, so I expect the sheet to conform to the flange. Thick gasket in there, too.

STF