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  • Tig consuming Tungstens?

    I was playing with my new dynasty 200dx, and trying to weld some 1/8" mild steel tube together, and I had a strange problem, at low current the arc looked nice, when I ramped up the current, the arc started wandering and the tungsten started to ball on the end, I could not seem to get enough heat to melt the metal. Eventually when I started ramping up higher (100-125A) the tungsten started to ball on the end (the tip just blunted out), and eventually melted all over the inside of the cup, I cut and reground several times (with different bevels, I tried making one not so pointy for higher current capacity), and the problem kept recurring, I could barely get the filler rod to melt, the only thing that seemed to melt nicely was the tungsten, until I got angry enough to stick weld it. I am using the heaver size tungsten (2% Thoriated) with the 150A torch and a #7 cup, approx 20cfh 100% Argon flow (I tried several settings), the tip is not protruding from the cup by more than 1/8", using DC tig process with HF start, no pulsing. Now by no means am I an expert tig welder, however I have done a little tig welding with this thing, mostly on thinner stock without trouble. I am 99% sure the polarity was correct (ground in left recepticle, torch in right). Any ideas?

  • #2
    illuzion,

    Here are a few things to try. 150 amps or so should get you where you need to be. The 3/32" diameter 2% thoriated is the correct tungsten choice. You can try 1/8" diameter, but it should not be necessary. The 3/32" will easily handle 30-150 amps. Blunt the point after grinding. This will put a flat on the end of the tungsten and cut down on tungsten boil off and arc wandering. Tungsten stick-out sounds right: 1 to 1.5X the tungsten diameter. If you are in or out too far it will burn off. Turn your gas flow down to 15 CFH. The 20 CFH may be creating turbulence and actually sucking in the atmosphere around the cup.

    What diameter is your filler fod? Do not use a filler in larger than your work. On 1/8" stock you can use up 1/8" filler. Sometimes I drop down. I have gone as small as .40 ER70S-6 filler on 1/8" mild steel. Too large a filler requires to much amperage to melt off and can create the problems you are describing. If you are not pushing the torch in as you approach the tube joint, then your arc gap is increasing and burning off the tungsten. This sounds like the first thing to try if all else looks correct. Yes, your polarity is correct. If all this fails, check the manual, not sure of page #-probably between 24 and 32, and reset the machine to factory defaults. It should not be out of wack, but it is possible. Keep us posted.

    Comment


    • #3
      Hawk,
      Thanks for the fast reply. Even without the use of filler metal, I cannot achieve fusion without melting the tungsten. I usually keep the filler rod about the same size or less than the tungsten I am using. If I ramp up the amperage, the metal gets hotter, but the tungsten just melts down faster. I have tried gas settings ranging from 10-20 CFH, no real change in results. I have paid extra special attention to the arc length, and I have it so short, I shorted out twice and reground the tungsten to remove contamination. From everything I have read this almost sounds like a reverse polarity issue (where all the heat is going into the tungsten and not into the joint), but I'm 99% sure I had it right. Any other ideas as to whats going on here?
      Thanks
      Brian

      Comment


      • #4
        brian,

        Try increasing your stick out a little. Also be sure to rest your machine to factory defaults. One thing about joining tube. You may be using too much amperage. Once you strike the arc use a counter-clockwise circle motion to create the molton puddle. This may take some time: 10-15 seconds or more if the tube is cold from lying in your garage. Just keep circling in the ccw motion about 1/8" away from your work. Once you get a good fluid puddle you can add filler and start moving the bead forward. As you continue to weld the steel will heat up and become easiet to work. My other thought is that your torch angle is not correct. About 10-15 degress of the vertical opposite the direction of travel is all the angle you need. A small angle off the vertical perpendicular to the direction of travel is also fine. If you can rest your torch hand against something (work table)to steady your torch movements while learning.

        Sometimes putting it down and walking away is good. Come back to it later. Tig is not easy. Do not try to go to fast. Be patient. take the time to learn and it will pay off. I easliy get $100 for 30 minutes of TIG time. Be patient and it will come. Frustration can be a motivator or your worst enemy.

        If things go well today maybe I can get you some pictures to go by.

        Comment


        • #5
          HAWK,
          I agree with you 100%, my fustration did get the best of me, after regrinding 4 times or so, I packed up and called it quits for the day. My main problem was creating a puddle. I could not melt anything except for the tungsten, I started by setting the power supply to a 110A max limit, and just after striking an arc using HF, and during ramp up (I don't even think I hit 100A), I could visually see the tungsten soften and start to melt, and even moving around I could not create a puddle. the metal got hot, but not nearly as hot as the tungsten. Correct me if I am wrong, if I just sit there and hold the torch still at 100A, it should just burn through the base metal and not the tungsten. All the other factors (torch angle, movement, filler, etc) just contribute to a good quality weld, and should not cause an instantaneous tungsten meltdown like I experienced. During ramp up, I just watched the tungsten end ball (it was ground to a blunted point) and then completely liquify, and drip right into the torch cup and freeze there. I know for sure gas flow was not a contributing factor, I varied between 10-25CFH with no noticable change in results. I assume reverse polarity would cause this. I assume this is why you are asking me to do a reset to default settings on the unit. What other possibilites besides reverse polarity could completely melt a 3/32 tungsten at 100A?
          Brian

          PS - as an aside, is there anyway to reverse the polarity for the SMAW (stick) process on this unit electronically???

          Comment


          • #6
            Brian,
            The torch should be connected to the right side plug marked 'electrode' and the work clamp connected to the 'work' or left side input. I think you stated that this is what you have, but I just wanted to confirm it. When you select the DC tig mode it should internally make the polarity switch so that for DC tig welding the torch is negative and the work clamp is positive. This is DCEN. Now if you change the process selector to stick, it changes the polarity of the electrode to positive and the work becomes negative. This is DCEP and is generally the correct polarity for stick welding.

            Now you seem to still have tungsten meltdown. Is your arc length 1/8" or preferably less? Is the tungsten tip black or blue when it melts down, or does it remain silver? Discoloration would point to air getting in. To put this issue to rest do this: Turn the machine on and put it in tig mode, but don't start welding or start the arc. Using a digital multimeter, put the neg. terminal of the meter on the work clamp connector and the positive terminal of the meter on the torch connection. It should read NEGATIVE 80 or so volts. If it reads positive, and you have the connections made as I described, then something would appear to be wrong with the machine. If you then switch the leads so that the torch is on the left side and the work clamp is on the right side and everything welds fine with no further tungsten meltdown, then this proves the point.

            good luck and let us know what happens.
            I'm sure you will.....

            -dseman

            Comment


            • #7
              H'mmm I wonder??

              Could it be that you are getting some boil off from the oil on the tubing..the new tubing I get has an oil on it to keep it from rusting before it gets to the customer..this oil can boil off from the heat and contaminate the welding field..

              Just wondering about this??? From what I have observed the edge prep needs to be absolutely clean in order to weld well..

              Maybe that could be a contributing factor to the difficulty..From what you have described the machine worked fine on some different material so just maybe it is something to do with this stuff that you are welding..

              The key piece in your post is that you welded some thinner material with no difficulty..

              Just my old brain thinking its usually something simple

              Grampa
              Grampa has done so much with so little now I do everything with nothing..;>)

              Comment


              • #8
                Boy that does sound like a polarity issue. It may be that the machine is not switching to EN during weld. Try going in to the hidden menu screen and changing the start polarity to - . It may be set for + .
                The proceedure for this is in the manual.

                Also, how does it do on Aluminum?? If the IGBT transistor switches were wired backwards, it would do what you describe. On Aluminum, the balance would work backward also with 99 being more cleaning instead of penetration. That would also ball the snot out of the tungsten. If you turn the balance the other way and it runs better, than I'd say that's the problem.

                Hope this helps.

                Andy

                Comment


                • #9
                  Thanks for all of the replies. Unfortunately I have been very busy the past few days and haven't had a chance to play. I called miller techline, and they agreed with me (and most of you) that this thing stinks of reverse polarity. I think the best thing to do at this point is configure for lift arc start (to prevent the high voltage start pulse from damaging a meter), and putting a digital meter on the output, and monitor the output polarity before and after tig arc start. From what the tech said to me unless the IGBT is miswired, what I am describing is nearly impossible. And yes, the start polarity can be changed, but once it starts, it will switch automatically to the proper polarity. So next time I get to play with it (probably thursday or friday), I plan on connecting a DMM to check the output polarity. As for people concerned about contamination when the electrode balls and melts down, it ends up with a highly polished silver color. And as for Grampa's reply, yes the tube I am using was oil coated to prevent rusting, I did degrease it and even grind some of it, and still cannot form a puddle or even get it to melt, and on top of it all, it is not even 1/8" as I originally had thought, it is actually 3/32, and it still wont melt! The miller tig calculator calls for a 1/16" tungsten at like 60-80A to melt this material, I am using a 3/32 tungsten at only 100A, and the tungsten is melting! I do recall seeing a spec somewhere that the reverse polarity capacity of a 3/32 tungsten with 100% Argon is only like 20-30A, so this seems the likely scenario to this point. The other thing I want to try is to duplicate this, and then reverse the connectors on the welder (torch on the left connector), and try it again.
                  Thanks again
                  Brian

                  Comment


                  • #10
                    Case Closed!

                    Ok found the problem, it is definately a reverse polarity issue. Preforming a default set seems to have cleared it, I was measuring a positive voltage at the torch with respect to the workpiece using lift arc. After default setting as per the manual, the torch is now negative and works fine, melted right through the tube at 90A without damage to the torch. Thanks for all the assistance. Btw- I also got a Spectrum 625 cover for my dynasty dx, and it does fit, but it is REALLY tight. I cut two slots in the top for the strap to fit through, so I can carry it with the cover on, and opened the velcro as much as possible. So far I am nothing short of impressed with this unit, across the board, I don't believe there is a better or more versatile unit available in the 200A range. Hopefully my speedglas helmet will arrive today so I stop getting flashed from the super smooth tig arc from this unit. Also why can I turn it up to 200A when only runnning on 115V, shouldn't it limit to 90A???
                    Thanks
                    Brian

                    Comment


                    • #11
                      Reset to Defaults

                      illuzion
                      sounds like HAWK had it in the begining when he suggested reseting it back to defaults... the new ones have a lot of buttons and menus to get tangled up in.... (maybe they ought to include an interface to your laptop to make status checks easier)
                      glad you are up and running
                      take care
                      Heiti
                      .

                      *******************************************
                      The more you know, The better you know, How little you know

                      “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

                      Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

                      My Blue Stuff:
                      Dynasty 350DX Tigrunner
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                      Millermatic 200

                      TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

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                      • #12
                        The unit will let you turn the amps up all the way but will measure the primary voltage while welding and apply a "rev-limiter" if you will when running on the lighter power supply. If you are on a strong line with higher voltage, you get more output power. This is why we don't just limit it to a fixed 90A.

                        Enjoy your machine...it's a killer unit!

                        Andy

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