Aluminum welding - backside bead wrinkling

Date 04-13-2009 21:21

I have some 0.350" 2014 aluminum that was welded via plasma arc welding. The top side of the bead looks nice and clean. The backside of the weld looks clean without any discoloration but the bead has a wrinkled appearance to it. If you run your fingers across it, there are ridges on the face of the bead. I'm assuming that this is due to lack of purge on the backside of this weld, but I'm wondering what the mechanism is for that kind of result.

Thanks.

By 803056

Date 04-15-2009 11:56

Without a root side purge, the hot molten aluminum is subject to oxidation. The oxide is essentially a ceramic with a higher melting point than the base metal and is hard and brittle. That's why aluminum oxide is used as an abrasive in grinding disks. As the weld puddle penetrates the base metal to produce melt-through, it "fractures" the aluminum oxide that has already formed giving the rough appearance you see when you turn the plate over to look at the root surface. Once formed, the oxide protects the weld metal from further oxidation, thus no root side purge is required provided the rough surface isn't a problem with your application of customer.

Best regards - Al