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  • Aluminum Certification test

    Hey guys, long time reader, first time poster..anyways... I need to take a cert test for a job. It consists of mig welding a .25" piece of 5052 alum to a piece of .25" 5456 alum, using 5356 for the filler. So the guy who the shop originally wanted failed 3 times due to porosity(spotted when xrayed) and I'm looking to be a step above this guy and nail this test. So far heres what I'm planning to do...I have the wheel of wire stored in plastic and loaded up with those moisture absorbing pouches, prior to testing I'm going to put the wheel in the oven long enough to bring it up to room temp. I'm also trying clipping some scotch brite in the wire feed to attempt taking off some oxidation of the wire before it gets to the metal. And then of course, acetone, wire brushing and preheating the base metal prior to welding.

    The boss man also wants me to try using a argon/helium mix for gas and supposedly I should run my machine (millermatic 450) in mig mode opposed to pulse?

    Anyone have some tips or tricks or correction to the process I'm about to attempt?
    Thanks!
    Chuck
    Charlie S.
    Miller AlumaPower 450 MPa
    Lincoln cv-300
    Miller Dynasty 400

  • #2
    This only my 4th post on this forum but not new to aluminum metallurgy.
    Porosity is caused by turbulence in the weld pool usually caused by insufficient arc current trapping the gases in the solidified bead.
    When the current is too low large droplets are formed.
    When the large droplet impacts the molten pool the gas is trapped.
    If the current is too high, metal is deposited over the gas bubble before it has a chance to escape from the molten puddle.
    Since the MIG process uses a constant voltage, increasing the wire feed rate will increase current.

    ​​​​​​To converge on the correct weld procedure to minimize porosity may require collection a few data points based on X-Ray results.
    Without any porosity data it is difficult to minimize porosity based on wire feed rate and travel rate.

    Porosity depends on how fast the weld pool solidifies.
    Increasing the current or decreasing the travel rate or both will increase the solidification time and allow more of the gas bubbles
    to escape before the pool solidifies.

    Also check the smoothness of the wire feed, since an irregular rate wire feed will cause excessive porosity.

    Use new wire spool that has not been previously unwrapped.
    Aluminum oxide on the feed wire will absorb water which will vaporizer to a gas in the welding process, adding to the argon and helium gases

    5052 has the best combination of yield strength and fatigue properties for AL and used extensively in commercial and military aircraft.
    Aluminum is quite sensitive to porosity, since the voids create stress concentrations serving as crack initiation sites for crack propagation from cyclic and vibration loading conditions.

    Bottom line, if the pool cools to fast, gas bubbles will trapped, i.e. porosity.
    Since AL conducts heat >> Steel, it cools >> faster.

    Comment


    • #3
      Originally posted by Charliebuckets1 View Post

      Anyone have some tips or tricks or correction to the process I'm about to attempt?
      Thanks!
      Chuck
      Yep, You're gonna need to practice with their stuff. Too many variables. And 9 days later we finally give you an answer. Sorry.
      Only one shot way is if "the BOSS" (or someone) can actually do it first, then hand you the gun.
      Otherwise, I question the reason for not using pulse. Not testing with it means not using it in the real situation.
      I have found pulse mig to be very handy in real world welding, esp. in out of position welds.
      Filler size is critical for this IMO. You didn't say what joint or position either.
      One of my pet peeves is letting you do everything on earth to pass the test, then they go crazy to fail you, only to later find out just how crappy of work actually goes out the door!!

      www.facebook.com/outbackaluminumwelding
      Miller Dynasty 700...OH YEA BABY!!
      MM 350P...PULSE SPRAYIN' MONSTER
      Miller Dynasty 280 with AC independent expansion card
      Miller Dynasty 200 DX "Blue Lightning"

      Miller Bobcat 225 NT (what I began my present Biz with!)
      Miller 30-A Spoolgun
      Miller WC-115-A
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      • #4
        Normally the welder is certified to a particular welding procedure.
        Before retiring was a pressure vessel and piping structural stress guy vin oil and gas industry then same type of job in the military and commercial aircraft industry were aluminum is the predominate metal.

        Where is the welding procedure?
        welding procedure includes, welding process, type of weld joint, geometry of the weld joint, position of weld joint
        If the procedure is GMAW, wire size, wire feed rate, voltage, travel rate ,preheat are required

        Seems like the employer is asking the welder to develop a welding procedure in three trails or less.

        The welding procedure is established first, then the welder certifies to an approved welding procedure.

        On the preheat thing, AL conducts heat 2X faster than carbon steel so the AL work will cool twice as fast as steel.
        This one of the reasons causing porosity in AL welding procedures.

        Based on geometry and joint type the weld joint may not be a candidate for welding using the GMAW method or any other welding method.

        Are Ford F150 light truck bodies welded, no , ..joints are riveted.

        Comment


        • #5
          Hey guys thanks for the tips, to answer some of the questions. The joint is a butt weld, in the flat position. With each piece having a 70 beveled edge and 3/16 gap between. And as far as the procedure goes...well that's the kicker, typically we're given a printed procedure as you would think, but for some dumb reason they're expecting us to create one as we go..lol. the only hint of a procedure we've been given is what grades of AL need to be welded, the filler material and that it needs to be done in 2 stringer passes... otherwise it's all on us. Also I've been long since said to **** with the bosses opinion on mig v pulse..it was clear after one try he was full of s**t on that one.
          Charlie S.
          Miller AlumaPower 450 MPa
          Lincoln cv-300
          Miller Dynasty 400

          Comment


          • #6
            I can tell you from personal experience-pulse is the way to go on aluminum mig. I worked at a plant that built aluminum petroleum tankers for the trucking industry. We used conventional mig until Miller trained 5 of our top welders on how to use pulse. After that, we used pulse, and never looked back. Our machines were the Miller 350MPa, with whatever feeder the maintenance department paired up with it. Beautiful welds with great puddle control, and, control over the heat input. Click image for larger version

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            • #7
              Nice!!

              www.facebook.com/outbackaluminumwelding
              Miller Dynasty 700...OH YEA BABY!!
              MM 350P...PULSE SPRAYIN' MONSTER
              Miller Dynasty 280 with AC independent expansion card
              Miller Dynasty 200 DX "Blue Lightning"

              Miller Bobcat 225 NT (what I began my present Biz with!)
              Miller 30-A Spoolgun
              Miller WC-115-A
              Miller Spectrum 300
              Miller 225 Thunderbolt (my first machine bought new 1980)
              Miller Digital Elite Titanium 9400

              Comment


              • #8
                Originally posted by Charliebuckets1 View Post
                Hey guys thanks for the tips, to answer some of the questions. The joint is a butt weld, in the flat position. With each piece having a 70 beveled edge and 3/16 gap between. And as far as the procedure goes...well that's the kicker, typically we're given a printed procedure as you would think, but for some dumb reason they're expecting us to create one as we go..lol. the only hint of a procedure we've been given is what grades of AL need to be welded, the filler material and that it needs to be done in 2 stringer passes... otherwise it's all on us. Also I've been long since said to **** with the bosses opinion on mig v pulse..it was clear after one try he was full of s**t on that one.
                So, do you get to practice for some time? Maybe during lunch or after work?

                www.facebook.com/outbackaluminumwelding
                Miller Dynasty 700...OH YEA BABY!!
                MM 350P...PULSE SPRAYIN' MONSTER
                Miller Dynasty 280 with AC independent expansion card
                Miller Dynasty 200 DX "Blue Lightning"

                Miller Bobcat 225 NT (what I began my present Biz with!)
                Miller 30-A Spoolgun
                Miller WC-115-A
                Miller Spectrum 300
                Miller 225 Thunderbolt (my first machine bought new 1980)
                Miller Digital Elite Titanium 9400

                Comment


                • #9
                  Oh yeah we've been going through a bunch of test pieces, doing dye checks on each one before even thinking about sending another one out for testing. I haven't been able to take the test myself, the job I'm on has too crucial and too pressing of a delivery date for me to be taken off the job. But 2 other guys have been doing it.. annoyingly tho I've been setting up the machine and test pieces for these guys cuz they're inexperienced with AL. So anyways we've sent out 4 failed tests and looking like we got a good one today, but we'll see
                  Charlie S.
                  Miller AlumaPower 450 MPa
                  Lincoln cv-300
                  Miller Dynasty 400

                  Comment


                  • #10
                    Used to work with a "welding engineer "" ,who developed the actual weld procedures.
                    Otherwise have use the trial and error method to establish the weld procedure.
                    The pulsing method, mentioned previously, is quite affective in bridging the 3/16" wide gap on the beveled full penetration butt joint.

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                    • #11
                      Charlie S.
                      Miller AlumaPower 450 MPa
                      Lincoln cv-300
                      Miller Dynasty 400

                      Comment

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