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  • #46
    Dcen

    Now that I think about it, isn't MIGing aluminum done with DCEN and straight argon? If so, why is there such a difference between it and TIG? Or is there (I haven't done MIG on aluminum yet)?

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    • #47
      Originally posted by kyoders View Post
      Now that I think about it, isn't MIGing aluminum done with DCEN and straight argon? If so, why is there such a difference between it and TIG? Or is there (I haven't done MIG on aluminum yet)?
      I was always taught that AC was used for GTAW AL because the electrons flow both ways...back and forth with the alternation of current...which allows an extra amount of cleaning-action to be performed by the electrons and also allows less penetration into the base material. Many times less penetration is wanted with aluminum, not more.

      I think one of the reasons someone made the comment about all of us remembering how unbelievably CLEAN the welding environment is/was when the DCEN + (He) setup was used was referencing the fact that DCEN could be used (as opposed to AC) simply because the environment was so clean and the additional cleaning elements allowed by AC GTAW weren't needed. Sheesh...hope that didn't sound too circular.

      There are probably several other reasons as well.
      HOBART Champion 10,000
      HTP MIG 2400 c RSG250 Spool Gun
      HTP Invertig 201 AC/DC - WANTED!!
      Lincoln PrecisionTIG 185
      Smith O/A Rig
      Clark 1/2" Floor Drill Press
      Clark 6" Bench Grinder
      DeWalt 4.5" Grinder
      DeWalt 4.5" Grinder #2
      DeWalt 4.5" Grinder #3
      B&D 18V 3/8" Drill
      B&D 18V 3/8" Impact Driver


      Now in order to kill the enemy, our men must be roused to anger; that there may be advantage from defeating the enemy, they must have their rewards. ~Sun Tzu in "The Art of War"

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      • #48
        Also, several weeks ago (i think about 6 weeks ago??) MAC, Sundown, Dan, and Sberry were attempting to explain to me the difference between spray-arc transfer and short-circuit transfer when MIGing and I seem to recall several posts in there about why GMAW was performed with DCEN and how the electrons moved between the wire, contact-tip, and base material. Reading those posts coupled with whatever you learn on this post might steer you in the right direction.

        Hope that made sense.

        ~Clint
        HOBART Champion 10,000
        HTP MIG 2400 c RSG250 Spool Gun
        HTP Invertig 201 AC/DC - WANTED!!
        Lincoln PrecisionTIG 185
        Smith O/A Rig
        Clark 1/2" Floor Drill Press
        Clark 6" Bench Grinder
        DeWalt 4.5" Grinder
        DeWalt 4.5" Grinder #2
        DeWalt 4.5" Grinder #3
        B&D 18V 3/8" Drill
        B&D 18V 3/8" Impact Driver


        Now in order to kill the enemy, our men must be roused to anger; that there may be advantage from defeating the enemy, they must have their rewards. ~Sun Tzu in "The Art of War"

        Comment


        • #49
          Originally posted by kyoders View Post
          Now that I think about it, isn't MIGing aluminum done with DCEN and straight argon? If so, why is there such a difference between it and TIG? Or is there (I haven't done MIG on aluminum yet)?
          nope, Al GMAW is DCEP w/ Ar, some FCAW (self-shielded) is DCEN.

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          • #50
            Originally posted by GTA/Spec View Post
            Here are some pics compairing the DC GTAW process with helium to an advanced squarewave GTAW with argon. Helium almost doubles your input wattage, and induces heat into aluminum faster than the aluminum can sink it. Thus the aluminum welds like steel or stainless.

            The first pic shows a fillet joint on .5" 6061 plate. One is AC one is DC
            Pic 2 shows the cross section of the AC weld
            Pic 3 show the cross section of a DC weld

            Travel speed on the dc weld was more than double than the AC weld. Even with a dynasty
            Originally posted by Pangea View Post
            If you wait to see a puddle form, you will blow a hole. Look for a discolored circle about the size that the puddle should be. Stab it with your filler wire and get ready to move out. Once you get the wire added, it gets easy to see. You can chase your wire too. that way is easier and leaves a smoother bead. Chasing wire is frowned on by lots of welders but it is the best way on aluminum/lithium alloys and lots of aerospace welders do it.

            When chasing rod, you can push extra rod into the puddle at a steady rate to carry a bigger bead, or pull the rod away slowly to leave a smaller bead.

            It just takes practice. I have 29 years worth.
            Originally posted by Pangea View Post
            I'd use lab grade helium,25ish CFH. 2% thoriated 3/32 tungsten ground like I posted above, about 140-155 amps or more if you like to move fast. 4043 wire also 3/32 with the end clipped. No oscillation. Grind starts and stops.

            But that's just me. Feel free to change any of those numbers to suit you.
            Originally posted by Pangea View Post
            Cleaning the parent material is one of the key elements to ensure a weld that will pass the strict requirements we are held to. We wire brush with a soft stainless wheel or stiff stainless steel tooth brush to remove alodine coatings if they are present. Acid etch, wire brush again, then srape the faying surfaces.

            On repairs we use a cutter wheel and a highspeed air grinder. The grinder has had acetone run through it, then alcohol to remove all oils. Air grinders don't last long that way. After cutting to remove discontinuities(porosity or tungsten inclusions from VPPAW) we wire brush the immediate area and weld asap.

            The 2% thoriated tungsten is ground to a 30ish degree angle with a flat tip. The flat tip will keep you from getting tungsten inclusions from shedding. The flattened area of the tip is about .005 to .015.

            The rest of the WPS is proprietary information. Try amperages and shilding gas flows close to what you would do with steel.

            Terminate the weld by back tracking and tailout on your rod. Grind starts and stops to eleminate cold laps and startup porosity.

            If there is anything else you need to know, feel free to ask.

            Good luck.
            What sort of setting would be appropriate for 1" thick 6000 series material fillet weld? All I have is 200A. I saw a good welder take a root pass at 115A but it didn't quite fuse.

            For some reason I am interested in learning this. I guess I will just run lots of beads on 0.25" to learn to see the puddle and then try fillet welds and move up in thickness.

            Yes know this thread is old but the information is precisely what I was looking for. Old books have lots of good stuff in them, too

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