Erratic Tig Arc with Puddle Blow-out

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I have been mig welding for 20+ years. I am new to tig with about 3 months of practice. I have dozens of hours practicing on mainly aluminum. I have a project requiring running 3/8" to 3/4" aluminum for a stabilizing rig on a fishing boat. My machine is a: Lincoln Tig 300/300, code 9401 which puts it at about 1997. Transformer machine without AC balance control,CK 230 Rigid torch rated to 300 amps,1/8" zirconiated tungsten,# 8 cup with 1/8" tip out.Amp setting High,Spark continuous,Remote pedal control,AC mode.Gas is Argon and Helium. I am trying to mix about 75/25 for penetration.Flow is about 20 cfh combined.The aluminum is large pieces, 10"x12"x3/8", and some thicker, smaller pieces joined to 3" aluminum pipe schedule 80, or about 3/8" thick walls. I am doing mostly T-joints. I get intermittent arc instability at mid range in the pedal. I can power up to form a puddle but when I try to give it more amps it blows the aluminum out of the puddle. It doesn't seem to get hot enough to flow the puddle. The beads are not pretty, and it looks like the material never heats fully. I have to go slow to get the penetration to the bottom of the inside corner and keep the keyhole forming.It looks like the tungsten is breaking up at high amps but that is why I went to zirconiated, to avoid electrode breakdown above 200 amps. I have more power available in the machine but when I try to use it the puddle just seems to blow up. I did some projects on thinner alu with mixed results. But I did get the job done. Any ideas? Joe
Reply:Pre heat with a O/A torch..Make the parts black with the soot from just the Acetelyne..Turn up the oxygen until your blue flame then heat the parts until the soot goes away and then weld away..You will see a huge difference.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Hello Ironwood, you said that you were fairly new to TIG, considering that statement are you sure that you have all of the connections to your machine properly connected. I am in no way trying to be condescending or a smarta**. I am asking because in the event that your leads are reversed on your machine it will play heck with how it welds. When the high-frequency is applied to the lead connections of the machine they have to be in the correct phase. Having the leads incorrectly connected could result in some of what you have described. So, is the ground hooked up to the "work" post and the torch hooked up to the "electrode"? If so, then obviously there is possibly some other sort of thing going on. I noticed in your intial post that you mentioned a #8 cup with "1/8" tip out", are you indicating that you have the tungsten extended an 1/8" beyond the face of the cup? If so, I would alter this stick-out to 1/2" and keep the end of the tungsten in tight to the puddle, just above actually touching or contacting it. This is where you may actually be having an issue with the puddle "blowing out". Having your tungsten an excessive distance from the weld puddle will dissapate the energy of the arc and not focus it properly to provide a clean and controlled weld pool. The excessive arc length requires you to "hammer down" on the pedal to try to get enough heat directed properly and causes an over-heating of the tungsten causing tungsten erosion and transfer into the base metal through the arc column. A few thoughts for your consideration. Good luck and best regards, Allanaevald
Reply:Hello Ironwood, I should have clarified one of the points of my previous post. Referring to tungsten stick-out, the 1/2" dimension would be applicable for fillet welds, if you are going to be doing bead-on-plate, butt welds, or lap joints, you would probably select a stick-out closer to 1/4". Best regards, Allanaevald
Reply:Well I went back down to the shop tonight and switched to a Thoriated 1/8" tungsten. It seemed to work better. This baffles me as the Zirconiated was definitely spitting and it was not supposed to do that.It is only 45 degrees F' in the shop. The weldment I was working on was mostly suspended off the welding table. Should this temp cause problems? Tomorrow I will try both more stick-out and preheat wit O/A and see what happens. Is there anything that might be wrong in the machine itself to cause an erratic arc. It is intermittent issue but it is real. I would like to try another machine but I live on an island and there is not one I can access.Great forum, Thanks for you help. Joe
Reply:In doing the fillet welds, how much gas would you use with the 1/2" stick-out? Joe
Reply:Hello Joe, the 20 cfh you mentioned in your original post may need to be bumped up a bit due to the percentage of helium in the mixture of gas you are using since helium is so much lighter than air and especially argon. Having said that, how much post-flow do you have dialed up and is the tungsten staying clean once you have stopped welding and the post-flow gas has ceased flowing? Is there any additional possibility that you are experiencing a loss of shielding gas due to drafts or other turbulence around the arc? The next suggestion that I have for you is based mainly on a past experience of mine and without being specifically familiar with the design of your particular torch so this may or not apply. At the shop that I am in there are a number of different models of GTAW torches, one of our models of torches uses a fairly short collet to grip the tungsten. If this particular collet is installed backwards it will still grip the tungsten and hold it, but it will cause turbulence in the shielding gas delivery and adversely affect arc/welding performance. In other words check very carefully to insure that all of your torch components are correctly assembled. Good luck and regards, Allanaevald
Reply:I called Lincoln and talked to tech support. I told them I was using a #6 conductor for service instead of the #4 recommended in the manual. He told me to up the wire size and check the spark gap under load to see if it had a steady blue spark going. Also he told me to up the spark intensity as this would help the stability of the arc and clean better. The manual did not cover that adjustment in detail.I did add another conductor, made the other adjustments, and checked the spark gap under load. The arc stability seemed much improved, not totally stable but close. I am going to try it for a day and see if all is well. Zapster, can I get good results preheating with a large propane burner?Thanks for every bodies help. Joe
Reply:I wonder if there's a problem with your pedal...the arc should smoothly ramp up, which is not what you described.
Reply:Originally Posted by IronwoodZapster, can I get good results preheating with a large propane burner?
Reply:First, without seeing it, going on your description, it sounds like you might have a gas issue.Gut tells me you probably want to use a MIG for this.  3/8 fillet weld is no problem.  Melting into 3/4" might be a problem (preheat)If you insist on TIGTry it with pure argon.  If you can make a puddle you are OK.If its still giving trouble, try it with a second, known good bottle of argon.  There are plenty of people on this board that have had vexing issues with contaminated argon.  Balance more to electrode negative.  Someone else can comment on that machine but I suspect you could go 80% electrode negative and still get enough cleaning.Making your own mix, especially with gasses that vary widely in weight, is bound for failure.  I can tell you that Smith mixers very accurately balance the pressure.  Essentially two stages.  First stage drops bottle pressure to 100psi (each gas), 2nd stage closer to 50psi but perfectly balanced.  Then they use a calibrated mixer.  The output of that goes to a flow meter.  Smith mixers list for $1500 (ebay for $500+)Maybe your gas supplier can give you the exact mix.  For a price mine will mix anything I want.  And price could be 2x what pure argon costs.  For me, a low quantity buyer, it would take a week to get the gas.Other issues.If you have that box cranked to 300Amps, I don't think 1/8 zirconiated or pure is going to make it.  Lanthanated (if you can find 2%) or Ceriated is what you want.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Well, it is definitely doing better. I think it must be the larger supply wire. As for the zirconiated, that suggestion came directly from the Techs at CK Worldwide. But I have to say that it is not holding up well. I am going back to thoriated until I can get to the mainland.Manually mixing at the bottles seems to be working ok. The flow meters hold their settings for hours. I am trying for a 75/25 A/H mix. Just how sensitive is it to ratio?Does anyone have an opinion on the function of the spark intensity. I should have asked the Tech at Lincoln. The manual just says to keep it as low as you can. But the Tech seemed to say  it had better cleaning action and a more stable arc at the higher settings. The manual does say that you can increase it more by setting the spark gap electrodes to .020" from .015". So I guess they feel there are times when you would need more intensity. I think I will try it.Joe
Reply:Hello Ironwood, I believe the tech may have given you a bit of information that is likely incorrect. The high-frequency current (high voltage, low current radio frequency) that is superimposed over the AC current while welding with AC current is only used to help initiate the arc without requiring direct shorting of the tungsten to the work and to maintain a stable arc when the current transitions from DC- to DC+ and back to DC-. It does NOT help with the cleaning action, this is accomplished by the DC+ side of the AC current. So in other words, it can affect arc stability but not arc cleaning action. Before I made a comment to this thread I wanted to verify that I was correct on this point so I checked ESAB, Miller, Lincoln, and other sources, they all supported this information. Best regards, Allanaevald
Reply:So the problem with the arc came back today. In fact it got worse. I think it is the hi-freq causing the problem. If I push the pedal until it just makes contact, I can see it is the high freq that is breaking down. So I pulled a Weldcraft aircooled torch with a 12.5' leads. I was only able to run 200 amps because of the rating on the torch but immediately I noticed a big improvement. Not 100% but much better. I put the original torch back on and the problem returned. So, as I see it, it could be the torch, but not logical to me. Or it could be the 25' hose/cable run that is putting too much strain on a weak hi-freq circuit. My 25' hose is brand new. I did open the spark gap box and watch the points while I ran the torch. It was a steady blue spark jumping. Anybody have any ideas where I should head next. Joe
Reply:Hello Ironwood, in some of the information that has been included in this thread there is a discussion about "high frequency leakage", if you have a part(s) of your torch/lead that is/are damaged, the HF will leak and thus reduce the amount that is available at the arc to properly stabilize it. In certain instances, the power cable for "some" tig torch set-ups is not designed to be used with HF, it is essentially considered fit for "scratch start" use only. You might have to do a little digging to determine if this has any bearing at all. Aside from that, carefully inspect the output lugs on your machine, look at how the adapter for the torch lead and coverage gas connection is attached to the electrode lug, be sure that you don't notice any sort of arcing on the surrounding surfaces or that it appears exceedingly close to any source that could be a ground. Sometimes it is a reasonably easy test to check for HF leakage by welding in the dark for a moment or two. A bit easier yet if you have someone else who can do some welding while you turnout the lights and look. If you initiate an arc on your work table or other surface and then look away from that and look for any sparks coming from anywhere else this could give you a good idea whether HF leakage could be one of your culprits, the dark helps immensely to determine this. A few additional thoughts for your consideration. Good luck and best regards, Allanaevald
Reply:It sounds like contaminated gas to me, especially concerning the fact you are mixing your own. Try DC on steel, and see. What kind of tip are you using on your thoriated? Balled tips on thoriated always give me hell.Is there much, if any, black oxide on your beads when you are done?
Reply:There is some soot but I am in a drafty shop. I talked some more to the factory rep. Those guys are great. I actually talked to the guy that worked on the original design team. He really knew his stuff. It could be a number of things. The HF is braking down somewhere. I am going to get a 12.5' power cable and see if that helps. It may be the HF transformer is breaking down. It is not available from Lincoln. Tech said he could talk me thru rebuilding it. I welded for almost an hour today after I blew the machine out well. It worked almost perfect. Then it went to ****. I am getting tired of this. I tried welding the 3/8" alu at 200 amps and got almost nowhere. Even with preheat. Back on 300 it melted like butter. So I know I need a bigger than 200 amp machine. Thanks again for the support. I will get this figured out. Joe
Reply:I thought I would update  the thread with some more information. On last Friday I spent some time with John, the Lincoln rep, trying to determine what was causing my erratic arc. I was almost convinced that the high frequency was leaking away somewhere. John gave me some places to look and over the weekend I did that. I cleaned and blew out all the components of the High Frequency circuit with no real improvement.I got the machine warmed up on some long welds and was able to push past the point of the arc collapsing and would get some decent performance. It seemed to work better when I added filler. I was going over old welds and trying to make them look better and noticed that as I wove back and forth on the weld that the erratic arc was worse as I crossed the middle of the old weld and would improve as I went to the edges. So on Monday I called John again and gave him my latest symptoms. He said he thought what I was experiencing was called Arc Rectification. Here is a definition from the internet:                    ~~~~~~~~~ AC GTAW Arc Rectification~~~~~~~~For those of you that use AC current on your TIG aluminum applications and you may wonder about that occasional plasma arc instability that may occur in the TIG arc. The following is a brief description of AC arc rectification.During the AC cycle, the tungsten is both positive and negative and the electrons flow in two directions 120 times per-second from the tungsten to work and from the work to the tungsten. First the tungsten in the negative mode is a superior conductor than the metals being welding. When the AC cycle is in its negative mode the electrons will flow from tungsten to work. During the negative mode we have more stable electron flow than when the electron flow in the positive cycle in which the electrons flow from negative alum metal surface to the positive tungsten tip. Another reason for AC rectification is the condition of the aluminum weld surface. For example when welding multipass TIG welds one weld pass will remove the alum metal surface oxide, the next pass made on top of the weld may present a cleaner weld surface, (a weld surface that presents less surface oxides). When the alum metal surface has less impurities (less oxides) the HF used to reignite the AC arc may have a difficult time as oxides add to arc stability, (that's one of the benefits of oxygen or CO2 in a MIG gas to weld steel). Remember it's the argon gas molecules and tungsten positive cycle that provides the arc cleaning action. The positive cycle is when the electrons flow from the work (breaking up the minuscule aluminum surface oxides) to the tungsten, this provides the arc cleaning action. Once the alum oxides have decreased from the weld surface its harder for the HF to reignite the arc so we see arc stability issues also affected by the condition of the alum weld surface.Today we use square wave weld equipment to minimize the effects of AC rectification however the arc rectification will still occur, it's just less noticeable.
Reply:So after reading this I tried getting the filler started as soon as possible and practicing good technique and it is working out better. I had a pretty good week and got this job just about done. So what do you guys think? Has anyone run into this before? Joe
Reply:This is from the Miller site. It describes it pretty well:                          Advanced Squarewave PerformanceIn the mid-1970s, Miller Electric set the standard for AC/DC TIG technology when it introduced the Syncrowave® welding machine with its Squarewave AC output technology. Squarewave technology minimized the problems inherent with AC welding: arc rectification, arc stumbling, wandering and outages.Non-Squarewave machines usually exhibited these symptoms during the Electrode Negative (EN) to Electrode Positive (EP) transition of the AC sine wave. Sometimes, these older units 1) did not have enough "push" to drive the arc through the zero crossing and then re-establish the arc in the opposite polarity.If five or six EN to EP cycles failed in a row, it created another problem: the welding output began to resemble DC. If this occurs, a TIG machine reaches for open circuit voltage in an attempt to get enough voltage to re-establish AC welding output. Unfortunately, the excess voltage can cause current overshoots. This may produce tungsten spitting, which degrades weld quality.Squarewave technology shortened the switching time between EN and EP, so it created a more desirable arc. So desirable, in fact, that all higher end AC TIG machines now feature Squarewave technology (Miller's patent expired in 1994). However, not all Squarewave technology is created equal.The advanced Squarewave technology employed in an inverter-based TIG machine takes EN to EP switching time a quantum leap forward.Inverters use advanced power switching semiconductors (you might hear them called IGBTs) and microprocessor controls that operate thousands of times faster than "conventional" power switching devices and controls. As a result, inverters push the arc through the zero crossing very quickly. This very quick transition improves weld quality and consistency.Not all inverters are created equal, either. Miller's Dynasty 300 DX has a unique design advantage because it uses a full bridge rectifier. This costs more than a half-bridge rectifier other AC/DC TIG inverters use, but it permits using a smaller stabilizer. A stabilizer is the "electricity sponge" that maintains the arc when it transitions through zero. The smaller the sponge, the faster the transition. This gives the Dynasty 300 DX a truer Squarewave output than any inverter in its class, so it has the smoothest, most consistent AC TIG arc in the industry.
Reply:I know this is an old thread, but.Ive had the same problem as stated above a few times. After a lot of trouble it ended up being the rheostat for the arc intensity being broken. replaced it and all was good as new. BTW. Ive had this machine for 37 years and still runs great.