Aluminum gap spanning

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Sometimes when I work over a gap TIGging aluminum I have trouble I presume is gas coverage related. In Example; last night I welded simple handles on a tote box. The problem arose trying to lay 1/4" x 2" square flat plate on a 16 gauge surface that wasn't absolutely flat, and weld a filet. It tended to bubble black ooze, no this wasn't a sealed void where expanding gasses were forced to bubble through the weld.Has anybody experienced this, have you solved it? I feel gas purging would solve the problem, but can't think of an efficient way to do it.
Reply:Might a product like Solar Flux solve such issues? Thinking it through, I drill a hole in a concrete wall, don't go all the way through, I get myself up to the hole to blow it out, I get a face full of concrete dust. I think I get a similar phenomenon welding over a crevice between two pieces of aluminum. I could fill the gap with argon from another source, or maybe with Solar Flux. I can't think of a good way to get argon in there.
Reply:I was thinking a gas shield behind it?Any chance torch angle blowing Argon past the void induced a Venturi effect and sucked air into the void?TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Originally Posted by Drf255I was thinking a gas shield behind it?Any chance torch angle blowing Argon past the void induced a Venturi effect and sucked air into the void?
Reply:Willie,Are you sure there wasn't any kind of clear coating (anodize, powder, etc.) on the sheet you were trying to weld the 2 x 2 square to?   Even if you had brushed it off around the edges where you were going to weld if there was some of it left trapped under where you had the 2 x 2 square clamped on I could see it getting hot enough to burn and out gas into your weld and cause that problem.
Reply:No, cleaned first with acetone, then ground clean with one of those open grinder pads, then just before clamping together, a heavy brushing with a hand held stainless brush. On every other application this is clean enough. It was essentially a filet weld, a large not quite flat surface of 16 gauge to a 2x2x1/4" flat welded on two of four sides. At its widest the gap was less than 1/16". As I welded only two sides, air had a place to escape from pressure. I have the feeling the gas blew in forcing air back out. I found holding the arc back on the puddle helped some, but once things got dirty, they stayed a mess.
Reply:Originally Posted by Willie BNo, cleaned first with acetone, then ground clean with one of those open grinder pads, then just before clamping together, a heavy brushing with a hand held stainless brush. On every other application this is clean enough. It was essentially a filet weld, a large not quite flat surface of 16 gauge to a 2x2x1/4" flat welded on two of four sides. At its widest the gap was less than 1/16". As I welded only two sides, air had a place to escape from pressure. I have the feeling the gas blew in forcing air back out. I found holding the arc back on the puddle helped some, but once things got dirty, they stayed a mess.
Reply:Originally Posted by Willie BSometimes when I work over a gap TIGging aluminum I have trouble I presume is gas coverage related. In Example; last night I welded simple handles on a tote box. The problem arose trying to lay 1/4" x 2" square flat plate on a 16 gauge surface that wasn't absolutely flat, and weld a filet. It tended to bubble black ooze, no this wasn't a sealed void where expanding gasses were forced to bubble through the weld.Has anybody experienced this, have you solved it? I feel gas purging would solve the problem, but can't think of an efficient way to do it.
Reply:I'm reluctant to power clean aluminum then use acetone as I get bits of paper towel on every scratch. I wipe with acetone to remove oil etc. first to avoid smearing it in with the grinder. This cleaning process always works well except when two flat surfaces are face to face. Terry; it bubbles, bunches of grey "skin" on the surface, some black specks, some bubbles through the back of the puddle. I'm not sure what crust might be, I get grey skin I interpret to be incomplete shielding.
Reply:One thing I know that oozing of any type from a gap is bad.I think you're on the right track with the gas/contamination. I use the ss brush, then acetone after because where I have to work, I'm not sure I trust my ss brush to be clean of oils for sure.Do you preheat? I've found that this will not only help my weld consistency, but help with contamination as well. I think the preheat is purging moisture in my case. It could be true for you as well.Chay
Reply:Does your puddle ever explode? Like just pop and leave a porous divot? I have never experienced black ooze without the popping puddle. The poping puddle is definite foreign materialConstant Current Weldor.
Reply:No pop.
Reply:The "grey skin" Sounds like simply oxidation which melts at a much higher temp than the aluminum itself. It will appear to "ooze" when the aluminum is melted but the oxidation has not. Are you sure you are getting through the oxidation and down to aluminum with the stainless brush first?Miller Dynasty 200DXMiller 252 Miller 250xMiller Syncrowave 250Miller AEAD200 LegendMiller 375 Xtreme plasmaLincoln WeldPak 100Victor O/A
Reply:Originally Posted by AKmudThe "grey skin" Sounds like simply oxidation which melts at a much higher temp than the aluminum itself. It will appear to "ooze" when the aluminum is melted but the oxidation has not. Are you sure you are getting through the oxidation and down to aluminum with the stainless brush first?
Reply:It kind of sounds like you're over-cooking the puddle. Or getting a breeze through the gap. If there's any way to get some copper behind the gap, you may get trapped argon and a more forgiving heat range. I try to avoid power brushing. Just acetone/laquer thinners, then the "tooth" brush only. What amps, %cleaning and material thickness?SqWave 200Millermatic 190Airco 200 ACHypertherm PM45Boice-Crane Band SawVictor O/A
Reply:I'm going to try to send photos.Last is to show you what the face of evil looks like.
Reply:Four layers, 1/4" 13" long, 3/8" 2-1/2"long, 1/4" 2-1/2" long all cut from 2-1/2" 6061. Once the thick stuff was welded to each other, the handle was applied to the 16 gauge box. That's when trouble ensued, You'll say the welds are ugly, I consider it a triumph they look as good as that.Done with a Dynasty 280DX, 160 HZ, 70% EN 1/8" 2% lanthanated, gas lens with about 20 CFH argon. Machine at 220? controlled with pedal.
Reply:What type flap disk are you using in prep?  Pretty spaniel.30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30"  vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:I like a Larger size filler rod when bridging a gap,  Start on one side and keep the filler rod in the puddle washing the heat back and forth between the two sides....If you want to pretty the weld up go back to a smaller filler and run a cosmetic bead like it was fit properly to start with...Like your dog......Last edited by B_C; 11-30-2014 at 02:58 PM.  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Originally Posted by B_CI like a Larger size filler rod when bridging a gap,  Start on one side and keep the filler rod in the puddle washing the heat back and forth between the two sides....If you want to pretty the weld up go back to a smaller filler and run a cosmetic bead like it was fit properly to start with...Like your dog......