Invisible weld?

[tffy]

Hi guys! Have a project where the butt-weld (well, actually two 45 degree chamfered pieces coming together - think picture frame) used on pretty thin (85 thou thick) aluminum need to be 'invisible'.

The pieces are held together and the customer is okay with a small gap remaining between them - so the weld can only be on one side - hence allowing the other side to remain clean. Are there methods that would reduce/eliminate/allow me to remove after the weld operation the visible HAZ on the opposite side?

Thanks!

 

[CoryPad]

Resistance spot or projection welding can be invisible on one or both sides. Friction stir welding seems like it could meet your needs to.

 

[tffy]

Thanks, Cory! Are there any links or further information on those methods? Everything I am seeing online has a noticeable 'pockmark' on both of the sides of the Resistance spot and Projection samples.

Thanks!

 

[kingnero]

.085" is more than 2mm. can you not (tig/gtaw-)weld and grind/polish ?

 

[btrueblood]

EB welding can give very fine seams, but the joint design can be non-intuitive and it ain't cheap.

There are pulsed Tig micro-welding outfits that can do rather remarkable things. A vendor had one of these and used it to weld a .008" thick diaphragm to two 1/8" thick support rings, and have the resulting seam be invisible to the naked eye. The weld was done hands-off in a weld jig on a lathe.

 

[Duwe6]

Pulsed tig - GTAW - may work; are you aware that aluminum is the hardest metal to properly weld of all the metals normally considered weldable? Compared to aluminum, zirconium, titanium, Inconel, Hastelloy are a walk in the park.

 

[Tmoose]

How tied to welding are they?

How about a large area reinforcing corner bonded invisibly to the back side?

http://framewareinc.com/store/media...319eda06f020e43594a9c230972d/f/i/file_3_4.jpg

 

[tbuelna]

Since the OP stated that there might be a gap between the faces of the aluminum parts being butt welded, processes like friction welding or EB welding would not work. The only welding processes that would work with a gap between the parts would be something like TIG or MIG that uses a filler material. The excess weld material could be machined or ground flush to the adjacent surface after welding, but the weld HAZ would not actually be "invisible". The only way to get a weld joint that is truly "invisible" (in a metallurgical sense) would be to use some form of solid state joining like friction welding or diffusion bonding.

 

[MikeHalloran]

You could drill and tap blind holes, say .070" deep, in the back face, insert short studs and use nuts to retain corner doublers. ... if you have the depth behind the panel.

If not, you could mill a mitered half lap at each corner, and bond the pieces with epoxy or cyanoacrylate.



Mike Halloran
Pembroke Pines, FL, USA

 

[MintJulep]

Consider vacuum furnace brazing.