[Panagioti]

I’ll try to post what I know as succinctly as possible but forgive me if it’s a little long-winded.

Working on a Syncrowave 250, water cooled, ser. LA158321. I don’t know the vintage.

Job is 6061 T6 .190 thick, 2f t-joints. I am a machinist with limited welding experience, these are my first t-joints on aluminum but have successfully worked with steel/stainless a fair bit.

- Torch is a brand new CK Flex-Loc, new gas lens, 3/32" blue and gold lanth. tungstens both tried, sharp and blunt points both tried.

- Settings are ~210 amps, High Freq continuous (control on position 10), AC balance 10 (manual indicates this is 68% electrode negative), postflow - just enough to prevent tungsten discoloration.

- I have cleaned and set the spark gap to .008, cleaned and tightened the posts, and even checked the ground cable for resistance.

- The material was prepped with IPA, dedicated stainless brush, and/or Scotch Brite wheel. The tungsten, filler rod, and table surface were also IPA’d.

My problem is that I cannot get a nice teardrop shaped arc cone that will penetrate into the corner of the t-joint. My cone is truncated, like the dunce cap I had to wear in school, with the large end of the cone presented to the work. Nothing I do will tighten this up, the arc just dances all around, randomly swapping from the one part to the other. I’ve tried every combination that I’ve watched or read online, never getting an acceptable arc. I’ve tested the AC Balance control and it does at least function at the extremes so I don’t think it’s that. I’ve tested with both slowly bringing up the amps, and mashing the pedal at a higher setting (as recommended by some). When a higher amperage is used and the pedal mashed, it will blow a 1/2" hole through the 3'16" material in a second or two. I don’t imagine that’s right but I think it at least rules out an insufficient line source. These t-joints are 3/16" from the edge and the arc will randomly jump over and melt the corner, it doesn’t matter where I’ve got the pedal, or at what angle I approach, it just won't burn into the corner. Even when running beads on flat plate, the cone’s truncation causes the bead to be too wide, it’s only possible to tighten it up by backing way off of the pedal, but then of course, I get no penetration. I found a couple of practice plates from a few years ago and they had nice tight beads with adequate penetration so I’m believing that this has worsened over time or is a new problem.

If this is a board issue rather than something I’m doing wrong, I have the ability to test and replace components if someone knowledgeable can point me in the right direction. If it’s something I’m doing, I’m more than willing to test any suggestions. Thank you.

[bap_]

Do you have a second tried and true torch you can try? If not what size gas lens cup are you using? The arc will wander with the shielding gas sometimes, you might have too much gas flow/big argon coverage?

I've really only used a #6 cup with about 12 CFH for all the AL I've done. Its a tricky beast for sure.

When you say ac balance at 10 is that cranked all the way? Try AC balance at 7/8?

[Panagioti]

Thank you for the reply.

Yes, I forgot to include those details. I was using a #7 cup with about 18cfh flow.

I do not have another torch but this one is brand new with new lines, etc. and it does weld just fine in dc.

I tried your suggestions just now with no change. I darkened up my helmet so I could really just pay attention to the arc and it is definitely bad. It spreads out from the tip like normal but just keeps spreading, it looks like there are three distinct needle-like arcs inside of the cone.

I just had a thought; how would an ac arc behave in the presence of Co2? Wondering if the gas company might have put mig mixture in my tank?

[Lightning]

When you say ac balance at 10 is that cranked all the way? Try AC balance at 7/8?

+1 ... or even 6/7.

OP, why do you have the AC balance way up on 10?

[Panagioti]

My manual states that a setting of 10 is 68% electrode negative, is this not where Jody recommends the balance for clean, new, material?

[cj737]

To me it sounds as though your tungsten has splintered. Did you by chance cut the tungsten in length? If so, how did you do it?

Always grind a tungsten in half. Snapping, cutting or slicing can cause micro fractures that will present a disturbed arc.

Another possibility is the arc length to the joint. Fillets can be tricky because the arc will prefer to grab one side or the other. Get right to the root and use your technique to avoid dipping. (This is not my suspicion based upon your description of the three-legged arc, but making sure you also verify this aspect).

[aeroplain]

Turn the balance to 8 and watch the trouble go away, or is that where you've got it? 3, or balanced is for DC as you know. I could be wrong on the setting, but at this point there seems little left to be wrong,and, as was stated above the electrode could be splintered.

[Panagioti]

To me it sounds as though your tungsten has splintered. Did you by chance cut the tungsten in length? If so, how did you do it?

Always grind a tungsten in half. Snapping, cutting or slicing can cause micro fractures that will present a disturbed arc.

cj737,
For this last test with the AC Balance control at 8, #6 cup, and the gas at 12cfh as suggested, I chose two brand new tungstens and ground one sharp and one blunt. I use a dedicated coarse diamond wheel and at one point, even finished off a few with a 1200 grit diamond finishing wheel that left an almost mirror-like tip, thinking that the problem might be the coarseness of the grind. I grind a good deal of carbide and am comfortable that I'm not chipping the tungsten, although I will from now on, wheel cut, rather than break off the contaminated end. Thank you for that advice.

Another possibility is the arc length to the joint. Fillets can be tricky because the arc will prefer to grab one side or the other. Get right to the root and use your technique to avoid dipping. (This is not my suspicion based upon your description of the three-legged arc, but making sure you also verify this aspect).

I am fairly new to TIG but grew up gas welding (farmer style) and the biggest fault I think have is keeping too tight of an arc and watching the filler rod swell up on my tungsten, I am confident in the respect that I'm not too long on the arc length.

Turn the balance to 8 and watch the trouble go away, or is that where you've got it? 3, or balanced is for DC as you know. I could be wrong on the setting, but at this point there seems little left to be wrong,and, as was stated above the electrode could be splintered.

aeroplane,
Tried the balance at 7 and 8 with no discernible change. If balanced setting is 3 (50/50 electrode positive to negative), and balance setting 10 is 32% electrode positive to 68% electrode negative, then each division is roughly 2 1/2 percent, so there isn't a world of difference between 10 and 8, at least the way I read it.

Regarding this AC balance, can someone please explain to me why the machine states that AC balance should be set to 3 for DC welding? A DC wave, unlike an AC wave is a straight line, is there AC leakage on the DC side in this machine?

[cj737]

A thought that occurred to me: do you have any pure Tungstens to choose from? If your Synchro is an older transformer unit, Green works really well. Heck, green still works on inverters though ceriated or lanthanated have advantages.

[aeroplain]

After re-reading the OP, are you sure that you're not expecting the arc and beads to behave the same as steel? they are different; as to the edge melting back, a heat sink would be of great value. The other thing that helps me focus when welding alu. is to where ear plugs. Alu. welding is noisy!! You won't get the nice narrow bead or as focused like you will with steel. I use the same machine and use pure tungsten because the boss won't buy Lanth. I bought my own and there is little advantage with the old transformer machine. Pure tungsten, set dial to 8, hi freq to continuous, 150-180 amps, 1/8 to 1/4 stick-out and haul ass.