We have been trying to find a defect free way to repair aluminum welds on 7/8" thick material and had no luck so far. We have some 7/8" 2219 material that is welded together using a GTAW DCEN program. The joint is j-grooved with a .125" root thickness. This joint is filled up with several passes with an automatic machine and 100% helium. With the automatic DCEN welds, we seem to have few problems with porosity because there is good control of welding speed, wire feed, etc. However, when we do have to make repairs we basically do the following - dig into the weld using a carbide cutting wheel slowly until the areas of porosity are removed. The removal is verified by x-ray. The welders groove this area out a bit so it's easier to fill. They wire brush the area, wipe with IPA and proceed to weld it with DCEN and 100% helium. This is done in the 2G position. However, more often than not these repair welds are full of porosity.
Since we're not getting any cleaning action from the DC, we figured it might be a good idea to switch to AC. We messed around all day today with AC on some sample material. We tried various gas mixes - 100% Ar, 75Ar/25He, 60Ar/40He, 75He/25Ar, various settings on our dynasty 700. The best looking weld we could make was using the parameters below
75Ar/25He mix
35CFH
Advanced SquareWave
260A EN
260A EP
75% Balance
185Hz
1/8" Ce tungsten
The bead looked fairly clean on the outside, but as we started to remove a little of the bead to check the inside, we saw clusters of pores. Obviously, welder skill is a big part of this too considering you have to go slow enough to let contamination boil out if there is any. Can anyone give some recommended settings, tips on torch angle, wire feed, or anything that might help us out? We don't really care which polarity we use, DC or AC, but we're looking for the best chance to produce clean welds.
Thanks
Zeek, please accomplish the required repair weld in the vertical position only, using upward progression only. Weld it hot incorporating slight preheat if necessary and your porosity issues will disappear.
Regards, Gary