Jagged appearance of backside of butt welds in aluminum

by Roy Parker

Hello, I'm welding .063 6061 in butt weld position. The upper weld looks fine, but flip it over and it looks like a jagged mountain range. I thought maybe I was pushing the rod into the puddle too far, but results are the same when I make sure to just barely touch the rod to the puddle.I've tried changing my speeds etc, can't figure out what I'm doing wrong. Have had some smooth welds mixed with the jagged but don't know what I was doing differently. Also, I've been told you don't have to run backing gas on aluminum. Is this true, or is there some benefit to backing gas on aluminum? I use argon for torch and backing gas. Any help would be greatly appreciated. Thanks.

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argon is not 100 percent necessary on the back side but does help quite a bit.

also, i find that i get a much smoother root if there is no gap, and the edges are filed very smooth to get rid of the rough sheared edge that holds oxides and such.

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