Al 5083- Horizontal weld

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I have a problem when welding Aluminum 5083 with position PC (Horizontal), the surface look nice but there are many porosity in side (see the attached pictures). This problem in PA (flat) and PF (vertical) is much less. The defect mostly happen in the root layer.The setting of my welding is:- Welding machine DP400- OTC.- Process MIG- Materials: 5083, thickness= 10mm.- Weld filler: 5183, d=1,2mm.- Current: DC pulse, 140A- Gas: Ar 100%, 20 liters/minute- Joint type: V-single side 90 degree, full penetration, no backing. gap=0-0,5mm.- Grinding disk: Inox grinding disk to remove 0,1mm x 20mm in both side.- Runs: 3 layer with 6 runs.Hope if any one can give me some idea about this. It makes me really headache. Thanks very much,Trung Attached Images
Reply:Open gap at the bottom with the mig process; the root will always have a little inclusion of varied contamination or carbon fouling which will show up as porosity.Easy fix is to 2 side bevel and weld pass bottom. Or, start with a root pass and use a carbide bit ti remove almost all the root pass from the top before running the fill passes. You will grind out nearly all contaminants and the fill should be better.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Hi Rojodiablo,Thanks for your advice. I will try this way. Will show you the result afterward Trung