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Why does fluxcore have better penetration?

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  • Why does fluxcore have better penetration?

    Everyone says fluxcore has better penetration capabilities.

    All other things being equal, why is that?

    Educate me, I'm ready.

  • #2
    I believe flux core will definitely penetrate deeper that solid wire / gas, all other things being equal. I'm not sure why that's true, but have always assumed it was because the gas kept the weld cooler.......sort of like blowing on hot soup
    -Bob (JalopyBldr)

    HH187
    13" SBL

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    • #3
      The reason FC has better penetration, is related to "arc density". There is less metal in the end of a tubular wire, which compresses the arc forcing it deeper into the base metal.

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      • #4
        It's "current density".

        Flux core has much greater penetration than any other manual or semi auto process for a given amperage.

        JTMcC.

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        • #5
          Current density is the ratio of current (amps) to the cross sectional area of the electrode.
          This is the reason flux core deposition rates are so high as well.

          JTMcC.

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          • #6
            http://www.esabna.com/EUWeb/AWTC/Lesson2_18.htm

            Keep reading through the GMAW process, which mentions Current Density first, and the on to FCAW
            Ed Conley
            Screaming Broccoli, Inc
            http://www.screamingbroccoli.net/
            MM252
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            Miller Passport Plus, Spoolmate 100
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            "Hold my beer while I try this!"

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            • #7
              A bit more info here: http://www.esabna.com/us/en/educatio...e-benefits.cfm
              --- RJL ----------------------------------------------

              Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
              -------------------------

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              • #8
                Originally posted by Broccoli1 View Post
                http://www.esabna.com/EUWeb/AWTC/Lesson2_18.htm

                Keep reading through the GMAW process, which mentions Current Density first, and the on to FCAW
                Great link to lots of good info.

                The tests are fun too. I got a 90% on chapter 1 and an 88% on chapter 2. That was after reading the chapters though. I've cleared up a lot of questions that I had in just two chapters.

                Thanks for the link.

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                • #9
                  Could it be that polarity also has some effect? With GTAW (TIG) the greater penetration is seen with straight polarity (DCEN) which is the same polarity used with self shielding flux core wire. The reverse polarity used with solid wire would put more heat into the wire rather than the weldment.

                  Ken

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                  • #10
                    Originally posted by taylorkh View Post
                    Could it be that polarity also has some effect? With GTAW (TIG) the greater penetration is seen with straight polarity (DCEN) which is the same polarity used with self shielding flux core wire. The reverse polarity used with solid wire would put more heat into the wire rather than the weldment.

                    Ken
                    The trouble with that theory of yours is that gas shielded flux core also has great penetration compared to solid wire and it runs on DCEP.

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                    • #11
                      I believe that gas shielded flux core is usually used in spray transfer mode which is a whole different thing. I recall from welding class that self shielding flux core in short circuit transfer mode is approved for some structural welds where solid wire is not. On the other hand solid wire spray transfer is approved for structural use.

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                      • #12
                        No code that I am aware of has restriction in regard to FCAW transfer mode.
                        "Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful."

                        -- Seneca the Younger

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                        • #13
                          Flux Core and Weld Penetration

                          As noted in another response above to read the information about this subject on the ESAB site,

                          http://www.esabna.com/us/en/educatio...e-benefits.cfm

                          I found the following as why their flux core mig wire results in a deeper penetration.

                          High Deposition Rates

                          The Dual Shield process is capable of high deposition rates because of the relatively high current density. The ratio of current (amperes) to the cross-sectional area of an electrode is known as the current density. The current density within a conductor will increase as the cross-sectional area of a conductor is reduced. Resistance to current flow through a conductor also increases as the cross-sectional area of the conductor decreases. Since the thin metal sheath provides the primary current path in a flux cored electrode, the resistance heating is concentrated in a very small area and the flux cored electrode reaches its melting point very quickly, resulting in high deposition rates.

                          Deep Penetration

                          Dual Shield electrodes’ small cross-sectional current path makes the arc stream assume a more columnar pattern, which contributes to their deep penetration. The deepest penetration occurs when straight CO2 gas shielding is used. This deep penetration results in an increase in the effective throat of a fillet joint. A fillet weld made with a coated stick electrode has shallow root penetration. When the effective throat of the fillet is increased because of deep penetration, the strength of the joint does not depend as much on the exterior size of the weld. Often times, the leg dimensions can be reduced and decreasing the fillet size by as little as 1/16" (1.6 mm) can reduce the total required weld metal by as much as 50 to 60 percent.
                          Last edited by bialecki; 12-12-2008, 03:52 PM.

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                          • #14
                            Originally posted by taylorkh View Post
                            I believe that gas shielded flux core is usually used in spray transfer mode which is a whole different thing. I recall from welding class that self shielding flux core in short circuit transfer mode is approved for some structural welds where solid wire is not. On the other hand solid wire spray transfer is approved for structural use.
                            Gas shielded Flux Core is used in globular and spray and everything inbetween. As far as I am aware, no Flux Cored wire, Self shielded or Gas shielded is run in short circuit.

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                            • #15
                              Flux core mig is a nonstandard term. It is describing two different processes. You can FCAW or GMAW (mig is a nonstandard term for GMAW using solid wire). It makes it difficult to follow the thread when you have trouble understanding what process is being discussed.
                              "Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful."

                              -- Seneca the Younger

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