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Miller Dynasty 200 DX - Internal Gas Leak

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  • Miller Dynasty 200 DX - Internal Gas Leak

    Hello all - it's been a while since posting.

    As stated in the title - I have a Dynasty 200DX and have been really struggling with contamination/oxidation on my welds. I started a small stainless project this week (1/16" sheet - 304 - small parts) and for the life of me I couldn't get a weld that didn't have a grayed out finish. using aluminum backing plate - but no back purging. Tried all settings - 40-65 amps - pulse/no pulse - travel speeds up and down - Argon from 10-25CFH. I verified flow at the nozzle. Did some reading on potential causes...bad gas, leaks, bad collet body, gas lens, cup...etc. For the heck of it...replaced the stubby gas lens/collet body/electrode/insulator - all new. Same result. Using a #8 Pyrex clear cup.

    I then tried the test I've read about in a few places - just holding the torch steady and producing a small spot weld...letting things cool while the argon times out post flow (Up to 20 seconds). No filler. I see a little improvement - but I expect to see a shiny spot - and I still get some "colors" (blues/purples). The HAZ around the spot does not seem symmetrical (which led me to replace the gas lens with new). By the way - the material is new, polished with new wheel - cleaned with acetone.

    Still getting gray cast oxidation running a short bead.

    So I started to trace all external connections and tested with soapy water - no leaks (regulator - right out to the connection under the handle of my CK Torch.) I took off the welder case cover (first time!) and CAREFULLY tested all the internal connections (rubber tubing to front and rear bulkhead fittings from solenoid) and found a very small leak at the front bulkhead fitting where the rubber tubing is clamped onto the fitting. Very small. It produces a couple bubbles but not anything crazy.

    I guess my question is - is this enough to contaminate the Argon? I don't mind replacing the tubing from the solenoid to the bulkhead fitting - just curious if others have had these very small leaks solve their oxidation/contamination issues. Any special type of tubing that should be used to replace the OEM stuff?

    Any thoughts are welcome.

  • #2
    If you are getting bubbles, that means some gas is leaking OUT. Plus it's under pressure. Gas will leak OUT. I don't see how that contaminates the shielding.

    Comment


    • #3
      I have no experience with a small leak like that, but I would guess that if you know you have a leak, and are getting symptoms of contaminated gas.....as the doctors say, when you hear hoofbeats, look for horses, not zebras. My guess would be that the gas is leaking out and showing you the bubbles when the system is just sitting there pressurized, but perhaps when gas is actually flowing, you are getting air drawn into the stream through the leak via the venturi effect, contaminating your weld. I don't know for a fact, obviously--perhaps someone with more experience will comment, but I'd sure fix the leak before looking anywhere else. Just an old guy's thoughts.

      Comment


      • #4
        A couple small bubbles isn't likely losing enough gas to cause poor shielding... especially if you verified flow at the nozzle.

        However, as to the actual problem, I can't help much there... I'm new to this whole TIG thing, and haven't even tried stainless yet. But, I'll take a few stabs at it anyway!

        Are you using DC, torch negative, work positive?

        If you dunk the torch in a bucket of water, do you get a whole lot of bubbles, from the cup and not elsewhere? You may want to pull the dinse connector first, and the torch should be cold.

        Are you using a regulator with an actual flow meter (the tall cylindrical gauge with a floating ball), or one with a fixed orifice and a pressure gauge? The latter are often unreliable.

        On youtube videos, I've seen people using extremely large cups and trailing shields when they really don't want any color on stainless. Also, back gas, so crap can't be sucked from the back side of the metal.

        Do you have another bottle of gas you can try?

        Do you have a full-size gas lens instead of a stubby to compare?

        Comment


        • #5
          Thanks for all the comments folks. Just to be clear, I was doing all the leak testing while the argon was flowing (just set a long post flow and initiated a weld cycle). The place I saw the "leak" is not pressurized until the weld cycle is initiated (solenoid opens the valve). I replaced the tubing and I still have a problem. Did notice the HAZ seems much more symmetrical - nice and round. (maybe I was getting a little air draft disruption of the argon earlier? )The trouble shooting continues ....

          My torch setup had remained the same - flow gauge at the regulator matches the floating ball test at the cup. I don't have any cups larger than a #8. I can try a larger cup - but I don't see why I can't even produce a nice shiny spot weld with the number 8 (5 second preflow/10 second post flow at 20CFH)

          Comment


          • #6
            So I have to ask, does it really matter for the job if you are not getting "perfect" coloring or does it just bug you that you can not duplicate what you see on the internet? I do a fair amount of stainless and some welds are beautiful and some are just nice and sometimes you get a crappy one for whatever reason. Most just clean right up with a stainless wire brush. Although this might not be the case but trying to duplicate a picture of one weld over a whole project, although it is something to strive for, is usually a fantasy in the real world of daily fabrication.

            Not trying to stir the pot but just saying what I have found over years of being in the industry.

            Have you tried a new tungsten, not grinding but an actual new one? What size torch, what size tungsten are you running?
            Last edited by MMW; 07-16-2020, 11:08 AM.
            MM250
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            Lincoln ac/dc 225
            Victor O/A
            MM200 black face
            Whitney 30 ton hydraulic punch
            Lown 1/8x 36" power roller
            Arco roto-phase model M
            Vectrax 7x12 band saw
            Miller spectrum 875
            30a spoolgun w/wc-24
            Syncrowave 250
            RCCS-14

            Comment


            • #7
              Originally posted by MMW View Post
              So I have to ask, does it really matter for the job if you are not getting "perfect" coloring or does it just bug you that you can not duplicate what you see on the internet? I do a fair amount of stainless and some welds are beautiful and some are just nice and sometimes you get a crappy one for whatever reason. Most just clean right up with a stainless wire brush. Although this might not be the case but trying to duplicate a picture of one weld over a whole project, although it is something to strive for, is usually a fantasy in the real world of daily fabrication.

              Not trying to stir the pot but just saying what I have found over years of being in the industry.

              Have you tried a new tungsten, not grinding but an actual new one? What size torch, what size tungsten are you running?
              Not at all stirring the pot - I don't have that much experience in stainless - so you are absolutely right/correct to question my motive/goals To your point, no these are not food/medical/xray quality welds I'm trying to achieve (cosmetically or physically) - but am looking to other sources - internet included - to gauge what I should/could be getting. And you are also correct, all of my welds in stainless so far clean up very easy with a quick swipe of a wire brush (dedicated to stainless). I didn't expect or need those "perfect" glamour shot welds - but couldn't understand why I hadn't been able to get rid of the the gray cast/contamination on such a short weld that I thought I was controlling the heat input fairly well (amps, travel speed, filler feed). Even the simple spot welds seemed "dirty".

              I actually appreciate the candid/real world feedback from more experienced folks.

              Using a CK Worldwide torch - 17 style/air cooled/flex hose. Running 3/32 2% Lanthanated (Also from CK) - brand new!.

              More experimentation....wondered about too much gas flow - and turned it back down to around 12-15CFH. It may have actually improved things a bit. Maybe I was getting some gas turbulence?

              Comment


              • #8
                How are you preparing your tungsten?

                What is the configuration of the weld? (Outside corner, t-joint, etc...)

                Comment


                • #9
                  Here is what I use on 1/16" material. 1/16" 2% thoriated tungsten, #9 air cooled torch, #6, 7 or 8 cup depending on joint, stick out also depends on joint but usually about 1/8", for gas I have a flow meter and set it so the ball rides between 15 and 20, amps I set about 100 and use the pedal to dial it in. Then I weld and keep welding until I dip it or notice it's not welding so good, then re grind, usually by hand on a non-dedicated bench grinder. Lately I've been chucking them in a cordless drill though. Don't think I switch cups and stickout constantly though as I pick what's best when I start and then weld.

                  The other thing to remember when looking at pics on the web that usually people only post the perfect ones. I do a bunch of these stainless frames, all 1-1/2 tubing, 1/16 wall. On each frame maybe I get half a dozen welds that are perfect. The rest are good, acceptable or what ever you want to call it. Sometimes you get a blowout when it becomes pressurized and that screws up the weld. You grind it a little and re weld that area, just part of the business. Don't get to hung up on getting it perfect every time. When I do get it perfect though I usually admire it. Second pic is a corner joint wire brushed and definitely not perfect spacing. Third pic is butt weld before brushing and you can see it's greyish.

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                  Last edited by MMW; 07-17-2020, 06:03 AM.
                  MM250
                  Trailblazer 250g
                  22a feeder
                  Lincoln ac/dc 225
                  Victor O/A
                  MM200 black face
                  Whitney 30 ton hydraulic punch
                  Lown 1/8x 36" power roller
                  Arco roto-phase model M
                  Vectrax 7x12 band saw
                  Miller spectrum 875
                  30a spoolgun w/wc-24
                  Syncrowave 250
                  RCCS-14

                  Comment


                  • #10
                    You mention a dedicated for stainless wire brush. I hope it has stainless wires and not steel wires you just use for stainless?
                    MM250
                    Trailblazer 250g
                    22a feeder
                    Lincoln ac/dc 225
                    Victor O/A
                    MM200 black face
                    Whitney 30 ton hydraulic punch
                    Lown 1/8x 36" power roller
                    Arco roto-phase model M
                    Vectrax 7x12 band saw
                    Miller spectrum 875
                    30a spoolgun w/wc-24
                    Syncrowave 250
                    RCCS-14

                    Comment


                    • #11
                      Originally posted by ryanjones2150 View Post
                      How are you preparing your tungsten?

                      What is the configuration of the weld? (Outside corner, t-joint, etc...)
                      Sorry - been away for a few days. Just doing a butt/lap joint. Tungsten prep for me hasn't changed...I use a cordless drill holding the tungsten against a dedicated wheel.

                      Comment


                      • #12
                        Originally posted by MMW View Post
                        Here is what I use on 1/16" material. 1/16" 2% thoriated tungsten, #9 air cooled torch, #6, 7 or 8 cup depending on joint, stick out also depends on joint but usually about 1/8", for gas I have a flow meter and set it so the ball rides between 15 and 20, amps I set about 100 and use the pedal to dial it in. Then I weld and keep welding until I dip it or notice it's not welding so good, then re grind, usually by hand on a non-dedicated bench grinder. Lately I've been chucking them in a cordless drill though. Don't think I switch cups and stickout constantly though as I pick what's best when I start and then weld.

                        The other thing to remember when looking at pics on the web that usually people only post the perfect ones. I do a bunch of these stainless frames, all 1-1/2 tubing, 1/16 wall. On each frame maybe I get half a dozen welds that are perfect. The rest are good, acceptable or what ever you want to call it. Sometimes you get a blowout when it becomes pressurized and that screws up the weld. You grind it a little and re weld that area, just part of the business. Don't get to hung up on getting it perfect every time. When I do get it perfect though I usually admire it. Second pic is a corner joint wire brushed and definitely not perfect spacing. Third pic is butt weld before brushing and you can see it's greyish.
                        Thanks out or the info/tips and reality check! Nice looking work. I'll continue down the path I'm on, I don't think I'm too far off. Just need more seat time with stainless. I've done a few destructive tests on some of the joints (180 degree bending right on the joint) and it's solid - see no signs of cracks or voids - so not worried about the strength side of the equation for what I'm doing. And yes, using a stainless steel wire brush dedicated to stainless welding.

                        Comment


                        • #13
                          I would switch to 1/16 tungsten and try a long tapered point.
                          MM250
                          Trailblazer 250g
                          22a feeder
                          Lincoln ac/dc 225
                          Victor O/A
                          MM200 black face
                          Whitney 30 ton hydraulic punch
                          Lown 1/8x 36" power roller
                          Arco roto-phase model M
                          Vectrax 7x12 band saw
                          Miller spectrum 875
                          30a spoolgun w/wc-24
                          Syncrowave 250
                          RCCS-14

                          Comment


                          • #14
                            How are you cleaning the material? Material that thin should be cleaned on the back side of the joint as well.

                            If the torch is held too high, or you have too great of a push angle, that will cause your problem.

                            You didn't mention filler, is this a fusion weld?

                            At that amperage I would use .045" or .035" dia. filler. Too large of filler will
                            slow down your travel and cause you to add more heat which will cook the base metal very quick.

                            Can you post some photo's?
                            Richard
                            West coast of Florida

                            Comment


                            • #15
                              Originally posted by MMW View Post
                              I would switch to 1/16 tungsten and try a long tapered point.
                              Thanks - I'll add it to the potential changes.

                              Comment

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