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Dual Shield Flux Core Welding Class at Hobart

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  • Dual Shield Flux Core Welding Class at Hobart

    For the past two weeks I attended a dual shield flux core welding class at the Hobart Institute of Welding Technology in Troy Ohio. It was the sixth Hobart class that I attended. Hobart has two basic welding class series: Structural, which is five months long and Pipe, which includes structural and is ten months long. Most of the students take the pipe class. The first shift class, which I attended was from 8 till 4, with one hour off for lunch. The first week we welded 3/8” plate and the second week we welded 1” plate. There was one written test each week and every different position of weld was tested. In my case all of my welds were tested with a bend test. If I had been enrolled in the entire series, they would have tested my 1” horizontal and overhead welds by a CWI and an X-ray test. The students that passed the CWI and X-ray tests (which was most of the class) received a AWS certification. I could have paid extra for the additional testing, but for $350 I chose not to. To pass the course you have to pass all of the written and weld tests. Every few weeks they start another group of students, so at any time they are actually conducting most if not all of the classes. This means that a student like me can take any class at pretty much any time. I took my first class in 2008 and every few years I took another class. I actually scheduled this class two years ago, while I was still working, but it was canceled due to Covid. The two-year delay was due to my stent and hernia operations. I really enjoyed the class, but I should point out that I was the slowest student in the class in terms of getting welds done. I was also the oldest student in the class.

    I just did a very slight weave for the root pass

    1. Horizontal root
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    As directed, I did all stringer beads for all of the horizontal welds.

    2. Horizontal cover
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    3. Cutting test samples
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    4. Horizontal weld tested
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    I did a single weave pass for the first vertical fill pass. Some people did two beads instead.

    5. Vertical first fill pass
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    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Lincoln LE 31 MP
    Lincoln 210 MP
    Clausing/Colchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport

  • #2
    I did a single weave pass for the cover. They told us that keep weave passes below one inch.

    6. Vertical cover
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    7. Vertical test samples
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    8. Overhead cover
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    The sample passed even with the cracks, because the cracks didn’t occur on the weld. The fact that I quenched the sample before I ran the cover pass, might have contributed to the cracks. It is ok to quench practice welds, but it is a bad practice to quench test welds. My bad.

    9. Overhead test samples
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    10. Overhead root
    Miller Thunderbolt
    Smith Oxyacetylene Torch
    Miller Dynasty 200DX
    Lincoln SP-250 MIG Welder
    Lincoln LE 31 MP
    Lincoln 210 MP
    Clausing/Colchester 15" Lathe
    16" DuAll Saw
    15" Drill Press
    7" x 9" Swivel Head Horizontal Band Saw
    20 Ton Arbor Press
    Bridgeport

    Comment


    • #3
      I chose to use multiple weave passes for each fill level.

      11. Overhead fill pass
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      12. Overhead cover
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      For the one-inch-thick plates we cut 3/8” strips and side bent them. If you look closely, you can see the weld profile in the test sample.

      13. Overhead test samples
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      14. First fill pass
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      15. Fill pass
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      Miller Thunderbolt
      Smith Oxyacetylene Torch
      Miller Dynasty 200DX
      Lincoln SP-250 MIG Welder
      Lincoln LE 31 MP
      Lincoln 210 MP
      Clausing/Colchester 15" Lathe
      16" DuAll Saw
      15" Drill Press
      7" x 9" Swivel Head Horizontal Band Saw
      20 Ton Arbor Press
      Bridgeport

      Comment


      • #4
        16. cover pass
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        If I had run straight stringer beads it would have taken ~21 passes. I used narrow weave beads instead.

        17. Run on tab
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        18. Vertical test samples
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        Last edited by Don52; 10-10-2021, 03:19 PM.
        Miller Thunderbolt
        Smith Oxyacetylene Torch
        Miller Dynasty 200DX
        Lincoln SP-250 MIG Welder
        Lincoln LE 31 MP
        Lincoln 210 MP
        Clausing/Colchester 15" Lathe
        16" DuAll Saw
        15" Drill Press
        7" x 9" Swivel Head Horizontal Band Saw
        20 Ton Arbor Press
        Bridgeport

        Comment


        • #5
          So what’s your take away, Don? Do you love DS wire now or what?

          Comment


          • #6
            Originally posted by ryanjones2150 View Post
            So what’s your take away, Don? Do you love DS wire now or what?
            I really like dual shield flux core welding for the following reasons.
            • It has great penetration on thicker metal
            • It has a high deposition rate
            • I can use my existing $2k welder with knurled feed rollers to run it.
            (As opposed to purchasing a $6k spray pulse welder)
            • The slag holds the puddle in place so it is great for out of position welding.
            • It is faster than stick or TIG welding
            • It makes less smoke compared to self shielded flux core (or stick), so I am comfortable using it inside my shop.
            -Don
            Miller Thunderbolt
            Smith Oxyacetylene Torch
            Miller Dynasty 200DX
            Lincoln SP-250 MIG Welder
            Lincoln LE 31 MP
            Lincoln 210 MP
            Clausing/Colchester 15" Lathe
            16" DuAll Saw
            15" Drill Press
            7" x 9" Swivel Head Horizontal Band Saw
            20 Ton Arbor Press
            Bridgeport

            Comment


            • #7
              Good Job Don, I marvel in how you take the time to get into different types of welding of which I think that is great. And having a teaching facility nearby obviously helps. I know I could use a tune-up once in a while as my eyes start to fade under the hood would love to have a school nearby.

              Most of my welding was split between stick using 7018 & some 7024 on my equipment out in a field with a BobCat....or Tig welding CroMo on racing chassis or aluminum.........One dirty out in the elements laying in the mud the other in a heated shop...My current tools are a Bobcat ( of which it hasn't ran for a while) (2) 211 Miller Migs ( one transformer the other inverter) and a Miller 280DX. I must admit that I'm more interested now in gluing something together quicker , than getting into the technique of either styles although all have there net value.

              So getting back to your Dual Shield Flux Core welding were you using a shielding gas? or is that optional? and does the polarity change between the two? will this process run outside in the weather?
              Keep up the nice work...

              Comment


              • #8
                Originally posted by tarry99 View Post
                Good Job Don, I marvel in how you take the time to get into different types of welding of which I think that is great. And having a teaching facility nearby obviously helps. I know I could use a tune-up once in a while as my eyes start to fade under the hood would love to have a school nearby. Keep up the nice work...
                Thanks

                Originally posted by tarry99 View Post
                So getting back to your Dual Shield Flux Core welding were you using a shielding gas? or is that optional?
                Dual shield flux core welding uses a inner shield of flux and a gas outer shield. Lincoln calls the process Outer shield for this reason. In our case we used 75%Ar 25% CO2 shielding gas. The gas is not optional. If you turn off the gas or have too long of a contact tip to work distance, you will get terrible porosity as shown below.

                29. Porosity due to inadequate shielding gas
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                Originally posted by tarry99 View Post
                ​​​​​​​Does the polarity change between the two?
                You typically use DCEP (reverse polarity) for both short circuit MIG and dual shield flux core.

                You typically use DCEN (straight polarity) for self shielded flux core welding.

                Originally posted by tarry99 View Post
                Will this process run outside in the weather?
                The shielding gas will blow away if there is any wind, so it isn't a robust process like self shield flux core or stick welding for welding outside. If you use it outside you would need to constructs barriers to block the wind.
                Miller Thunderbolt
                Smith Oxyacetylene Torch
                Miller Dynasty 200DX
                Lincoln SP-250 MIG Welder
                Lincoln LE 31 MP
                Lincoln 210 MP
                Clausing/Colchester 15" Lathe
                16" DuAll Saw
                15" Drill Press
                7" x 9" Swivel Head Horizontal Band Saw
                20 Ton Arbor Press
                Bridgeport

                Comment


                • #9
                  Hi Don. What wire were you using? Brand, number and size. Just curious. Nice work on the tests.
                  MM250
                  Trailblazer 250g
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                  • #10
                    Originally posted by MMW View Post
                    Hi Don. What wire were you using? Brand, number and size. Just curious. Nice work on the tests.
                    At home I am using:
                    .035" Lincoln Outer Shield 71M wire

                    .045" Kobelco Frontiarc-711
                    At the Hobart class we used:

                    .045" E71T1 wire (Don't know the brand)

                    -Don
                    Miller Thunderbolt
                    Smith Oxyacetylene Torch
                    Miller Dynasty 200DX
                    Lincoln SP-250 MIG Welder
                    Lincoln LE 31 MP
                    Lincoln 210 MP
                    Clausing/Colchester 15" Lathe
                    16" DuAll Saw
                    15" Drill Press
                    7" x 9" Swivel Head Horizontal Band Saw
                    20 Ton Arbor Press
                    Bridgeport

                    Comment

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