Announcement

Collapse
No announcement yet.

Aluminum alloy differences and cracking when cooling?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Aluminum alloy differences and cracking when cooling?

    I have a job coming up welding an extruded aluminum sailboat mast. The weld will be on the bottom, where Akkad the weight will be, plus the force of the cables. I have used tons of 4043 over the years, but I suspect this might require a better grade, but 6061 has a tendency to crack when cooling, right? Is there a 50** series that would split the difference? Or, why has my 6061 welds cracked in the past? What should I be doing different?

  • #2
    Setting asside the welding aspect of your post . . . .

    I suggest You may want to understand more about the mast,
    and what caused the needed repairs, or what is desired by modify-ing it?

    Got pics? This could be a mess in the making.
    sigpicViceGrip
    Negative people have a problem for every solution

    Comment


    • #3
      Originally posted by vicegrip View Post
      Setting asside the welding aspect of your post . . . .

      I suggest You may want to understand more about the mast,
      and what caused the needed repairs, or what is desired by modify-ing it?

      Got pics? This could be a mess in the making.
      The mast was in an ocean boat, exposed to salt water. It looks like it was standing in 4" of chicken poop.
      The actual work will be similar to welding a badly damaged prop.
      I am just concerned about which filler rod to use. I see there are a couple rods in the 50s series, but I am still a little unsure of their exact properties. I have never used T6, but I maybe erroneously, thought it was prone to cracking easily as it cools.
      Last edited by BMWSID; 05-23-2014, 07:23 AM.

      Comment


      • #4
        I worked in a shop that made airframe replacement parts from time to time, for what was then
        Midwest Express airlines, that did full service on DC 9's here in Milwaukee.

        I got a shop tour one afternoon, and couldn't keep up, absorbing all the information
        their heat-treat expert was giving me. Much off it directly opposite of what
        I ever would have guessed.

        I use this info to this day, but I have the lattitude to experiment, untill I get
        the results or effects I'm after. I'm hestitant to just openly dump here in public.
        HOWEVER; Weldaway has vast experience that I would hazzard a guess
        might cover what you're get'n at.

        I'd shoot him a PM, or an Email or both, see what he might have to say.
        Phil

        PS;
        The mechanic in me, and haveing been raised by a Mariner Father an expert at Sailing
        and boat building, I would be looking at "refooting" the mast with a fresh stump
        mechanicly transitioned "with regaurds to support and stesses".
        Some modification to the hull might augment a Class A repair.

        But that's just me, I Luv Rivits. Especially after the tour of the DC 9 shop.
        Last edited by vicegrip; 05-23-2014, 10:51 AM.
        sigpicViceGrip
        Negative people have a problem for every solution

        Comment


        • #5
          I have a few questions for you. Are you positive the aluminum is 6061? What has given you the idea for a 5000 series rod? What process are you using to weld? (Ex. Stick, tig, mig) do you have pictures of your past work that cracked?
          I am sure that I will have a more detailed question base and answers as you begin to answer to the thread. Aluminum is often approached with similar thinking as one would with steel. Aluminum is its own beast, and must be treated with a bit more respect. The wrong filler could mean failure in a years time. I am happy to help any way I can if I can, it might take some emails.
          Miller dynasty 350
          Miller syncrowave 250
          Miller deltaweld 450
          Miller cp-300
          And one fancy microwelding setup

          Comment


          • #6
            Aircraft Spruce has a pretty good little primer on the different aluminum alloys and their properties.

            General Aluminum Information

            Doesn't include any way to tell what type of alloy is used if the mill markings have been removed though, which would be helpful. Still an interesting read though.

            Comment


            • #7
              Thinking inside the box

              JB WELD ?

              Comment


              • #8
                Perhaps another "hit & run" inquiry ?

                Some people's manners . . .
                sigpicViceGrip
                Negative people have a problem for every solution

                Comment


                • #9
                  I only check back for so long, and then I don't worry about others problems.
                  Miller dynasty 350
                  Miller syncrowave 250
                  Miller deltaweld 450
                  Miller cp-300
                  And one fancy microwelding setup

                  Comment


                  • #10
                    From what I saw in my Navy days with aluminum superstructures exposed to saltwater, e.g. the aluminum lifeline stanchions welded to the aluminum deck tended to corrode excessively at the weld joint and caused constant failures.

                    Would think consideration in how to restore the anodizing to prevent aluminum oxidation at the weld joint would also need to be looked into, especially given the saltwater/atmosphere exposure.
                    Hobby Welder for about 32 years
                    Hobart 190 MIG with SpoolGun
                    Hobart AirForce 700i Plasma Cutter
                    Hornell Speedglas 9000X Helmet
                    295A AC Buzzbox (what I learned on)
                    Miller Bobcat 225, factory propane option, also serves as my emergency power generator

                    Dandeman Dan's Toy Page

                    Comment


                    • #11
                      Are masts welded in? I always thought that they were stepped into a base so that they could be removed for transport.

                      Comment


                      • #12
                        Welding the sailboat mast

                        Originally posted by Northweldor View Post
                        Are masts welded in? I always thought that they were stepped into a base so that they could be removed for transport.
                        Ok, the job is done. I did it with 4043. I spent an honest 4 hours under the helmet, not including the finish work with a paper wheel, making it pretty. About like fixing an aluminum propeller, but no need for balancing. It would have cost the boat owner 15K to replace the mast, so I saved him over 14K. Everybody is happy. I made sure I stressed they research putting some kin dog coating or finish to prevent that from happening again, but it will be in fresh water now, so not so immersed in sea salt. The mast fits through the deck down into the bilge, and fits over a stump of some sort, so I had to make sure there were no big bumps inside, too. The whole job was done off the boat, on saw horses, so yes, it was removed.

                        Comment


                        • #13
                          Glad to hear all this, but pics would put some spice in it !

                          Ahhh ? you did take some pics , right ?
                          sigpicViceGrip
                          Negative people have a problem for every solution

                          Comment


                          • #14
                            Originally posted by vicegrip View Post
                            Glad to hear all this, but pics would put some spice in it !

                            Ahhh ? you did take some pics , right ?
                            Yes, I did take some pics, but I don't seem to be able to get them on here from where they are, I just tried.

                            Comment


                            • #15
                              "It would have cost the boat owner 15K to replace the mast, so I saved him over 14K. Everybody is happy."

                              Everyone is happy for now.
                              Hope you got lucky. Happens sometimes.

                              Welding up aluminum without knowing the grade of the aluminum has a tendency to go very badly. Welding tends to anneal the aluminum (maybe not so big of a problem with the 5000 series depend on the mast design, only a few ksi drop in the yield strength). 6061-T6 mast, big problem anywhere from about 4/5th to 1/2 reduction in the strength of the mast in the weld area. 7000 series not good either.

                              Comment

                              Working...
                              X