Another TIG AC thread

admin

TIG and I haven't been getting along since my jump back into the process. Now I'm on aluminum. Here's some pics:In the first pic, the left bead ended abruptly several times. My breaker for the welder in the power panel is appearantly going bad so it was tripping causing that yellow stain you see there.The right bead in the first pic looks like absolute crap. And in the 2nd pic it was better but not all that.What I'm doing is building a welding table, yes out of aluminum. "Why," you may ask, because we have about 1/2 ton of 2" x 6" x 3/16" rectangular 6061 aluminum tubing thats been sitting for 10-15 years. So I'm building a 36" x 48" table out of it. I can always put a sheet of steel plate on top for tacking purposes.I've been cleaning the aluminum using a brand new stainless steel brush and have been heating the metal using a mapp torch (don't have an oxy/ace at home). Things I'm noticing while trying to run a bead is, obviously, severe porosity. This is when trying to form a pool, I see the metal pitting as I'm trying to melt it and when I get done you can see it shows in the final product.The setup I'm running is using my Millet TIG 180 with an 1/8" brown (rare earth) tungsten @ 180 amps with 3/32" filler with a gas flow of 18-20 psi.All helpful criticism is welcomed.Miller Syncrowave 180SDMillermatic 175
Reply:I'm not seeing enough cleaning. Clean the area 2 or 3 inches back before fitting them up. Give it a wipe with acetone after brushing. This includes the area that will be under the Tee joint. It looks like you're bridging the joint and not getting much pentetration at the base of the Tee. Fill the crater before stopping.
Reply:More cleaning with a wire brush. It looks like your shielding is not to good also. 20 CFH should be enough too. Is your tig torch assambled correct also. I've seen a guy get crappy welds like that before because his collet was in upside down. Beats me why it made his welds crappy but it did. Other than that what kind of filler are you using, make sure it not somehting like alladin filler that looks like aluminum but isn't. --Gol'
Reply:More heat, and more filler.
Reply:Comments about your weldment.PURE TUNGSTEN (green) for aluminum. Just read the side of the tungsten box if you do not believe me.Tungsten should be 3/32. Use a gas lens if possible. Did you form a ball on the end of the tungsten?The weld is COLD.The problem is that the plates are butted up against each other and you would actually want a small gap. Here is the reason: Aluminum gives off heat very fast, so if all those plates are touching each other, it all adds up to a lot of surface area giving off a lot of heat. Also you need a small gap for shrinkage and penetration to be certain. You need to make a tack weld on each end FIRST. The tack weld keeps the plates from creeping and preheats the plate so that the weld is not cold on the start and hot near the finish. With aluminum you want the plate to be warmed up.I also did not see any brush marks on the metal plate to clean it before welding. it needs to be brushed FIRST before welding. Use a small stainless tooth brush. You can get them at a welding store. If you weld two plates touching, and you do not tack them before welding, what happens is that as you start welding the plates get pulled together until they actually will start to overlap after a short distance. ALWAYS TACK all weldments BEFORE final welding.The result of all welding is SHRINKAGE. Think about that.It is good you are welding a joint and not just a flat plate. A flat plate is not a good practice. It is always good to prepare a joint then tack it. and then finsh  weld it.Do not worry about the collet being upside down. It is not possible because it is threaded only on one end.Last edited by Donald Branscom; 05-18-2008 at 03:22 PM.
Reply:All good comments, thanks, I'll clean the metal up some more and give it another crack tomorrow if I have time for it as well as pick up a new breaker for the power panel.I've actually had better luck with the rare earth tungsten in the past than I have with pure tungsten. The tungsten I have is brown striped, I coulda swore it was rare earth (don't have the box for the brown anymore, but the green I still do), but I did a color code check and it comes up Zirconiated Tungsten. But never the less, Zirconiated and rare earth tungsten are both superior to the the pure (green) tunsten commonly associated with AC welding. So that shouldn't be the issue, unless it's the size. As I said I've had better luck in the with the brown stripe than green but this is years ago. And yes it's balled.Reference via Miller's website:Pure Tungsten (Color Code: Green)1Pure tungsten electrodes (AWS classification EWP) contain 99.50% tungsten, have the highest consumption rate of all electrodes and are typically less expensive than “alloyed” counterparts.These electrodes form a clean, balled tip when heated and provide great arc stability for AC welding with balanced wave. Pure tungsten also provides good arc stability for AC sine wave welding, especially on aluminum and magnesium, but is not typically used for DC welding (it does not provide as strong of arc starts as thoriated or ceriated electrodes).Zirconiated (Color Code: Brown)Zirconiated tungsten electrodes (AWS classification EWZr-1) contain a minimum of 99.10% tungsten and .15 to .40% zirconium. A Zirconiated tungsten electrode produces an extremely stable arc and resists tungsten spitting. It is ideal for AC welding as it retains a balled tip and has a high resistance to contamination. Its current carrying capability is equal to or greater than thoriated tungsten. Under no circumstances is zirconiated recommended for DC welding.Rare Earth (Color Code: Gray)Rare earth tungsten electrodes (AWS classification EWG) contain unspecified additives of rare earth oxides or hybrid combinations of different oxides, but manufacturers are required to identify each additive and its percentage on the package. Depending on the additives, desired results can include: a stable arc in both AC and DC processes, greater longevity than thoriated tungsten, the ability to use a smaller size diameter tungsten for the same job, use of a higher current for similar sized tungsten and less tungsten spitting. I've heard in the past Lanthanated Tungsten is the cat's meow though. I need to get a new bottle of argon anyhow so I'm gonna pick up a packet of those. Supposedly you can weld AC and kept a sharp point on it. Worth the couple of bucks of bucks to try. Also need to pick up a new lens.Last edited by Kubs; 05-18-2008 at 07:56 PM.Miller Syncrowave 180SDMillermatic 175
Reply:Just a thought regarding you use of MAPP gas for preheat, don't put the flame directly on the joint.  Heat around it so you don't contaminate the joint with the impurities from the torch.
Reply:Originally Posted by Donald BranscomDo not worry about the collet being upside down. It is not possible because it is threaded only on one end.