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I have to weld a fitting on the bottom of a all-clad pot. The pot is stainless steel, with an alluminum layer bonded somehow on the bottom of the pot with another layer of stainless on the bottom sandwhiching the alluminum. Now my question is, is it possible to weld the coupler on the bottom of the pot without the alluminum core becoming a problem when I try to establish a puddle. My guess, its gonna burn back the alluminum, but Im not sure if it will throw porosity into the stainless steel puddle, or cause cracking. Any ideas?
Can't help on the chance (or more likely lack of chance) of successfully welding that. Manufacturing is done by high pressure bonding.. The spot weld two stainless sheets together at one edge, insert a sheet of aluminum between, and feed it through high pressure rollers. Then they press them to shape.
I doubt you'll get a sucessful weld without damaging the bond between the aluminum and the stainless so if it doesn't need to be sanitary, I'd second drill and tap for a standard threaded fitting.
If it needs to meet sanitary requirements, but doesn't need to be flush on the inside, I'd use a matching stainless tube and run a fillet on the inside (plain tube or with the tube flared) as small as possible and at as low a heat as will do the job to reduce risk of separation.
If it needs to be sanitary and flush on the inside, I'd bore all the way through the size needed on the inside, then bore oversize from the outside, removing the outer skin and the aluminum to the inner stainless layer. Then you will have a little clearance between where the weld needs to be and the bonded aluminum. If the heat is kept low, you might be able to avoid separation.
Thanks for help guys. These pots are not mine, so at $175 a pot, Im gonna let the owner figure out if he wants to destroy the cladding, or drill a hole in it. I will let him know what you guys mentioned, thanks again.