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MIG Welding Aluminum with a Spool Gun

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  • MIG Welding Aluminum with a Spool Gun

    Last spring I took a one week spray pulse MIG welding class at Hobart Institute of Welding Technology. We spent two days welding groove welds on 1" steel and three days on 3/8" Aluminum in all positions. The spray pulse welder made it relatively easy to weld both of these materials out of position. For Steel we used a conventional MIG gun and for Aluminum we used a push pull gun. The steel welds were tested with a side bend test and the Aluminum welds were etched to verify penetration.

    With this spray pulse experience behind me, I decided to try it out the spool gun that came with my MIG welder. I used 1/8" Aluminum stock because I have a lot of it and it is the thickness that I most often weld. I did the normal padding beads and welding test coupons to get the parameters dialed in as shown on picture 1. Overall it went well. The following parameters were used on all welds:

    Lincoln SP250 MIG Welder
    Lincoln A30 Spool Gun
    20-25 CFH Argon Shielding gas
    Coupons 1/8" x 2" x 6"
    No preheat -- welded at room temperature (I actually let the metal cool off before I welded the 2nd side)
    Push position of gun
    No weave or step ahead
    0.035" 4043 Aluminum wire

    I noticed that there was a little cold lap at the start of the weld as shown on picture 2 & 3.
    I believe that this could be several things could contribute to this:
    • No hot run in setting on welder.
    • Preheat of starting point of metal.
    • Increase the Voltage
    • Use a run in tab
    • Metal thicker than 1/8" would be able to tolerated higher voltage.
    • Could add some Helium to the Argon

    For my next run, I increased the voltage to 20.5 volts as shown in picture 4 & 5.
    This solved the cold lap problem but it created two new problems:
    • Suck back on back side of plate.
    • Undercut on top of weld.
    Attached Files
    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Clausing/Coldchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport
    Miller Spectrum 375 Plasma Torch

  • #2
    For my next test I tried a run in tab.
    This almost completely eliminated the cold lap.
    I'm sure that I could eliminate the cold lap completely with this method if I played with it, but really isn't practical for most of my real world applications.

    Next I did a Google search of every MIG spool gun welding video that I could find.
    Every single one that showed the start of the completed weld had cold lap at the start.
    The cold lap is clearly visible on the left side of the attached picture 7, which is from the Miller spool gun welding video.

    I am guessing that most people that weld 1/8" Aluminum with a spool gun don't worry about the cold lap at the start or they preheat the starting point before welding. The run in tab isn't practical because by the time you add the tab and remove it you wouldn't save any time over TIG welding it. One thing that I wanted to try is higher voltage with a step out motion to limit the heat build up.

    I know that a there are members have a lot more experience with the spool gun on Aluminum than I do and I would welcome their input.

    Don
    Attached Files
    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Clausing/Coldchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport
    Miller Spectrum 375 Plasma Torch

    Comment


    • #3
      Need aametalmaster to chime in. He's the spoolgun aluminum guru.

      Good info. Thanks for posting.

      Comment


      • #4
        Ditto, Nice post good info.

        Comment


        • #5
          Originally posted by Aeronca41 View Post
          Need aametalmaster to chime in. He's the spoolgun aluminum guru.

          Good info. Thanks for posting.
          I did send a personal message to asmetalmaster, but he has had problems getting personal messages.

          Don
          Miller Thunderbolt
          Smith Oxyacetylene Torch
          Miller Dynasty 200DX
          Lincoln SP-250 MIG Welder
          Clausing/Coldchester 15" Lathe
          16" DuAll Saw
          15" Drill Press
          7" x 9" Swivel Head Horizontal Band Saw
          20 Ton Arbor Press
          Bridgeport
          Miller Spectrum 375 Plasma Torch

          Comment


          • #6
            I think we all have.

            Comment

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