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Info from the Web on AC TIG aluminum.

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    Info from the Web on AC TIG aluminum.

    I am starting this thread with all of the helpful info that I got from https://www.youtube.com/watch?v=VOqhh36Kcxo. All credit goes to Jody Collier and the people who commented on that video.

    I can see that the information will be overwhelming so I will separate it into Settings, Cleaning, Troubleshooting, etc.I will be adding info to this all of July and August 2018.

    None of this is info from me. As I write this, I have never even lit up on aluminum. I am just collecting info from the internet to distill and organize.

    Last edited by commuter ebikes; 5 days ago.

    #2
    Why AC? What is different about aluminum?

    Aluminum has an exterior film of aluminum oxide which melts at 3600 degrees. Aluminum melts at 1200 degrees. AC offers electrode positive (EP) and electrode negative (EN). EP will give "cleaning action" (break up aluminum oxide on the surface, break through oxide layer), but EP heats up the electrode a great deal. DCEN provides penetration/heat input/sustainable electrode temps.

    From the comments:
    "Current flows from (+) Positive to (-) Negative, but electrons flow inversely to the current. The electrons dictate the heat input. Current flows from (+) Positive to (-) Negative, but because electrons flow inversely to the current, and the electrons dictate the heat input. EN puts heat into the work: electrons are flowing from the tungsten (-) to the work (+), and that causes the weldment to increase in temperature resulting in better penetration." This guy is saying that in EN, the tungsten is the "electrode negative", but the electrons are shooting on to the weldment, heating it up and resulting in high penetration.
    Last edited by commuter ebikes; 1 week ago.

    Comment


    • max_volt
      max_volt commented
      Editing a comment
      I didn't know that welders were trying to rewrite the theory of electricity. Ben Franklin erroneously thought flow was from + to -. What ever you call it current/electrons/ions it IS - to +. Why heat would occur at a certain junction is a horse of a different color.

    • commuter ebikes
      commuter ebikes commented
      Editing a comment
      I know that a welder or a physicist looks at it differently. I think that a welder thinks the way he does is because so much welding is DCEN so somehow the welders just want to fixate on the fact that their electrode is negative and their weldment is grounded (positive).

      In the above example of DCEN, are the electrons flowing into the weldment, thus the heat input and resulting penetration?
      Last edited by commuter ebikes; 5 days ago.

    #3
    Inverter vs. Transformer welders.

    With a transformer machine, round the tip of the electrode for welding aluminum.

    With an inverter power source, no need to round the tip of the electrode. It is common to leave a taper on the electrode.

    Quoted (with a little editing) from the video comments:
    "Inverters have features that allow you to change the waveform, like changing the AC balance percentage, pulse settings, frequency settings and even various wave forms. They're lighter, take up less space and use less power. A transformer, on the other hand, is simple, with less parts, less settings, less versatile, and costs less. Inverters are considered easier to weld with."

    A transformer machine will probably run at 60 Hz (1 Hertz = 1 cycle/second) because that is what comes from an electrical outlet https://www.millerwelds.com/resource.../tig-frequency. A transformer machine will run at a fixed 60 Hz. An entry level inverter welding machine will probably be set at 120 Hz. A pricier inverter machine will allow the user to vary the frequency. One is advised to go to a lower frequency for thicker material and cast aluminum, and consider bumping the frequency up a bit (for example, to 150 Hz) for thinner material. Miller likes 120 Hz as a starting point for frequency. Jody likes 100-120 Hz. The very high frequencies (e.g. above 300 Hz are usually used in robotic welders) because the benefits are so minuscule as to not be noticed by a human.

    Going to a lower frequency will put more heat into your weld.

    Going to a higher frequency will focus the arc and tighten the bead.
    Last edited by commuter ebikes; 1 day ago.

    Comment


      #4
      Settings

      Using the using "1A per .001" thickness of material rule of thumb", Jody used 63A on .063" (1.6mm) and found that this necessitated a slow travel speed.

      Increasing amperage to 75A on the .063" allowed a normal travel speed (10"/minute).

      A lot of people don't have a setting for an asymmetrical wave form, but a question was raised in the comments section about how the amplitudes of the positive and negative portions of the wave cycle affect the puddle, tungsten, and cleaning action. This has nothing to do with the AC balance, and I do not yet know the answer to this question.

      The Miller Dynasty 200DX has been said to be very picky about where you set the balance vs frequency.

      For 80A, try a preflow of 0.2s and a post flow of 3s.

      Adding helium to your shielding gas can help compensate for having a small machine. For example, you may only be able to weld a certain thickness of aluminum with a small machine, but adding helium to your shielding gas will allow the same machine to weld thicker material.

      Different machines have a different setting for what 70% means. Some machines it refers to the negative, and for others it's the positive. So for example, 70% AC balance on a Miller machine is the same AC balance as 30% on an Everlast.

      A possible setting for material thickness between .035" and .093" on an inverter machine: 3/32", 2% Thoriated Tungsten, 75% AC balance,160 Hz using a sine wave waveshape. Be prepared to go higher on Hz to get a tighter bead. The tungsten may ball up a fair amount with these settings, but that is okay.

      I connect my grounding cable (i.e. work clamp) into the positive terminal of my welder (it has a picture of a ground clamp where the Dinse connector attaches). I connect my torch into the negative terminal (it has a picture of a torch at the connection point). This is for DCEN TIG welding. I do not change it for AC welding. As I understand it, it would not matter if somebody hooked it up the other way around for AC welding because it is alternating back and forth between EN and EP anyway.

      A Miller Dynasty 200DX has been said to be very picky about where you set the AC balance vs frequency.

      An example of pre- and postflow for welding at 80A: preflow 0.2 s, postflow at 3.0 s.

      From the comments: "Using an Inverter machine, I use 3/32 2% Thoriated Tungsten. My tungsten tends to ball up a fair amount. I'm usually at 75% Balance & 160 Hz using Sine wave for the wave shape. Material thickness is usually around .035 - .093". At times I will go higher on the Hz to get a tighter bead."

      If you weld too slow, you are not using enough Amps, and this will increase your heat affected zone. It is best to keep a consistent short arc length, use a lot of Amps and move quickly.

      Set the amperage to 20-25% higher than your "suspected max amperage". You don't have to use it all. This gives you the ability to adapt and add heat as you go. When you get started, don't be afraid. Mash the foot pedal, get your puddle and then taper off as needed. Finesse the weld with the foot pedal.
      Last edited by commuter ebikes; 20 hours ago.

      Comment


        #5
        Helpful techniques (a lot of these are quoted nearly word for word from Jody Collier)

        Lift the tungsten up a little every time you add filler. The puddle tends to rise a lot so just long arc it a little each time you dab the filler in the puddle and then get back to it.

        Use an icepick to scribe lines in the material to see where you are going.

        Light up, barely tap the foot pedal, get the arc going Start pedal slowly (barely get any foot pedal going). After 3-4 dips, start mashing the pedal down gradually until it is full pedal (70A on .063"). When about 2-3 dips from the end, start letting off until the pedal is all the way off.

        Outside corner joints: one of the easier joints, you can make them look really nice, you can hold a lot longer arc than you can get away with on a lot of other joints.

        Tee joint: at the very beginning, light up and try to keep the puddle small. Tight arc, dab the rod try and get it joined, pause for just a minute to let the heat dissipate, and then get to moving. It's all about a tight arc and not too much torch angle. He happened to be using a #5 or #6 cup at this point.

        The reason to never long arc it: big arc plume caused by the long arc will cause arc to melt the rod to melt before it even gets into the puddle and cause too big of a puddle. It is hard to neck it down once it gets this big. This can cause porosity and lack of fusion (not getting heat into the root of the joint). Max arc length is 1/8".

        Inside corner joints: just about the same as a tee joint unless you happen to have some gap or something. Keep a tight arc. Move the puddle ahead and dab, move the puddle ahead and dab. Try and do it in a mechanized fashion.

        For thicker aluminum, consider preheating the material to 200-300 degrees F. Many people use a hot plate, but an over or toaster oven will provide the same result. You can also preheat with a propane or oxyacetylene torch A torch will burn off most of the oil residue and gunk.

        Keep aluminum and oxidation off the tungsten. Contaminated tungsten can be ruinous. If you dip the tungsten, cut off all the aluminum contamination with cable cutters (not side cutters!) before regrinding the electrode.

        Mixing in helium will allow a welder to weld thicker aluminum. So if your power supply has limited Amps, you can still use it for thicker material. Instead of buying a set argon/helium mixture, consider buying a tank of helium and a y-connector so that you can vary your mixture. From the comments: "A 200A machine welds like a 250A machine with a Helium mix. You don't need much Helium to see the effect. Helium ionizes at a higher voltage, power = Amps X Volts, so when you increase the Voltage it increases the power." Also from the comments: "The only time I ever use Helium is if the welder's maximum amperage rating isn't high enough...But I've noticed it requires more cleaning action on the wave balance to keep the weld bead and etched area looking as clean as when using 100% argon (not brown/dull). You can also pick up a bit of travel speed on thicker materials with a Helium mix."

        There is no substitute for hood time. The key to getting good is to practice.

        When first starting a new bead, give the cleaning action a chance to get well underway before adding filler.

        Consider preheating aluminum in thicknesses 1/2" and greater before welding it.

        Take the time to get great fit up. If it is good enough, you can even use an autogenous (fusion, no filler) weld.

        If you have a lot of starts and stops in your weld bead, you can make it look pretty by (1) filling the low spots with filler rod, and (2) passing over it in the reverse direction without filler. This is called "washing it".
        Last edited by commuter ebikes; 20 hours ago.

        Comment


          #6
          Consumables, including cups (i.e. nozzles) and shielding gas

          For the .063" plate, Jody was using a #6 gas lens, 3/32" tungsten with a slight taper on it, 2% lanthanated tungsten and 15cfh pure Argon. On 1/8" 6061 plate, he changed to a #8 cup.

          He was using both 1/16" (.0625") and 3/32" (.0938") rod in both 4043 or 5356 varieties.

          Consider a #5-#6 gas lens for 3/32", 2% lanthanated tungsten and pure Argon.

          Tungsten stickout should be no longer than the diameter of the cup. Use as little tungsten stickout as possible in order to optimize gas shielding. Along those same lines, torch angle for aluminum should be more perpendicular to the welding surface than it would be for steel. 90 degrees is not ridiculous; rather, it is ideal.

          Many aluminum welders will use a #5 cup up to 200A.

          If your electrode is oxidizing, this is a clue that you should increase gas flow.

          25 cfh should be enough gas flow. Too much gas will cool the weld and tungsten. Oxidized, colored or porous welds are an indication of too little gas flow.

          From the comments: "With 1/8" tungsten, a #6 or #7 ceramic cup will start to deform at about 250A."

          It is considered acceptable to use a back purge with aluminum, particularly with tubing and pipe. Use scrap steel clamped to the back of your aluminum at the seam, and the steel will not weld to the aluminum. Similarly, use scrap aluminum as an Argon dam when welding steel or Ti.

          When you go to a larger cup size, you need to turn up the Argon. Longer tungsten stickout (for hard to reach areas) calls for a larger cup size.

          Arc length should be the same as the diameter of the filler rod.
          Last edited by commuter ebikes; 20 hours ago.

          Comment


            #7
            Differences for welding on cast aluminum

            Increased need for cleaning action due to more oxidization and possibility of oil impregnation in the material. Let the cleaning action work before puddling. Run torch back and forth a little bit before adding rod. Coax the bead on kind of like a brazed (i.e. oxyacetylene with silver wire or brass rod) joint.
            Last edited by commuter ebikes; 5 days ago.

            Comment


              #8
              What not to do.

              Don't use too long of an arc because the big arc plume will melt the rod before it even gets into the puddle. A long arc also causes too big of a puddle; it is hard to neck down the puddle size once it gets this big, resulting in porosity and lack of fusion because the root of the joint never received adequate heat.

              Don't use red or blue Scotch-Brite pads as they have been known to leave a residue (moreso the blue ones).

              Don't use any brake cleaner products containing chlorine. Just to be safe, some people won't even use the chlorine-free brake cleaner.

              Don't forsake the health of your lungs. The fumes coming off aluminum are much more dangerous to your health than the fumes from steel welding. My helmet has an Adflo, and I never weld in a closed shop. The garage door is always open all the way (I have a 270 degree welding curtain to protect anybody who looks in).

              Don't try to weld 7075, 2024 or other nonweldable aluminum alloys http://www.esabna.com/us/en/educatio...num-alloys.cfm.

              Don't let your prepped parts sit for too long after cleaning or etching. Even after 4 hours (and certainly after more than a day), you will need to reprep the material as it will have oxidized.
              Last edited by commuter ebikes; 5 days ago.

              Comment


                #9
                Material prep.

                Taking the extra time to clean the weldment so that you are welding on uncontaminated shiny metal is always worth the time and effort. Certainly, get the oxides off. Choices include brown Scotch-Brite pads, SS wire brush dedicated to aluminum, acetone, denatured or isopropyl alcohol.

                From the comments: "4 inch Scotch-Brite pad on angle grinder, stainless wire brush (dedicated to aluminum!) to remove oxide layer. Wipe with alcohol or acetone. Before striking up, I hit it lightly with a small stainless hand held wire brush once more. Keep your TIG filler rods wiped clean. I have welded aluminum daily for 10yrs, and that is my routine."

                From the comments: "Why you don't you brush? I've welded 5000 & 6000 series alumunim since the '70's and always use a power brush (0.014" wire only) to clean the mill scale off. Then I re-do the brush using hand toothbrush immediately before I light up."

                From the comments: "Scotch-Brite disc removes only the oxidation layer. You would be really hard pressed to actually grind with one, and remove metal. I use the 4" green discs with rubber backing pad and Velcro attachment. They are around 3/16" thick. They leave a shiny, scratch free surface."

                Thicker material requires more thorough cleaning because it will see more heat.

                Prep parent material on both sides (even in a tube or pipe) because the weld will suck contaminants through, particularly on a butt joint.

                If for some reason you are welding on aluminum that has not been prepped so well, you can compensate for this by increasing the cleaning action (i.e. increasing EP) as well as the amperage.
                Last edited by commuter ebikes; 20 hours ago.

                Comment


                  #10
                  Troubleshooting.

                  Warpage:
                  Tack welds (every 6" ought to be enough) and/or chill blocks clamped to the weldment. Obviously, use only as much heat as you need to do the job; take a break between passes to let the metal cool.

                  Black Pepper in the Puddle:
                  Increase gas flow, make sure that there is no air getting in your gas line, prep material better (including where it was cut).
                  One shop found that their pepper in the puddle was due to a bad cylinder of gas.

                  Grainy Appearance in the Weld Bead:
                  Can be caused by air getting in to the gas line. Check torch for leaks.

                  If your parent material is grounded, you will get a puddle if you crank up the amperage and get the arc length right.
                  Last edited by commuter ebikes; 20 hours ago.

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