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cracking aluminum welds

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  • cracking aluminum welds

    Im trying to repair a crack in the aluminum action of my shotgun. it is a thin section over a threaded ID...and since it was a metric square style thread...I left the mating piece in place when i welded the aluminum( mating piece is steel) because i dont have a tap to clean out any deformation in the threads below the weld. Every time i weld it. it looks great.. then a little while...minutes.. a crack shows up in the weld.. I ve used un marked 1/16th dia rod, im thinking is 4340, and ive used 5356 rod, that i can read what it is. i still get the crack... Ive even cut out a 1/8th" wide section and welded in an insert of 6061. it welded GREAT.. then , it cracked... Im not sure of the aluminum alloy in the reciever of the gun. is this a thin wall-issue, next to a thick section cooling ISSUE? or could it be an alloy material ISSUE? Ive used a shallow weld setting... and i got a little contamination, but eventually the reciever heats up enough to get good puddling and it flows seemingly fine. Im trying not to get the whole thing too hot....and ive balled up a mound of aluminum. then Ive machined it back down, but the crack shows up.. then i tried a deeper pentrating setting...but I get the same crack.......ive played with the EN and EP, the setting is using a foot pedal.....1/16th lanthanated rod... on a Miller 350 dynasty....its a tricky little spot with not a lot of real estate, and ive welded it at least 5 or 6 times... any guidance is appreciated....
    Last edited by dvice; 01-22-2019, 11:56 AM.

  • #2
    Post a picture. Telling the doctor you have a mole and not pulling down your pants to show him isn't going to yield good results.

    And the unmarked rod...that's like the cop who pulls a guy over and see white powder on his lap? Sloppy doing a line of blow or icing sugar from a donut? Hard to say, they look so much alike?


    • #3
      or could it be an alloy material ISSUE? That would be My Guess .....Alloy , plating , anodizing


      • #4
        My bet is on a non-weldable alloy.

        A guy that has a dynasty 350 and can exactly describe what he's done is likely to be competent enough to make this repair if the alloy is repairable.

        Maybe resort to an aluminum brazing rod and give that a go.


        • #5
          It's a shotgun reciever. Its heat treated to a certain temper. It's got to be stiff and robust ^^^ I'm with Ryan. It's been molecularly changed to a nonweldable aluminum alloy.
          Dynasty 400 wireless
          Coolmate 3.5
          Sw320 speedway
          Ck flex lock 230
          4 victor flow meters
          2 Flametech Duel flowmeters
          2 genuine miller torch buttons
          A$$ loads of tungsten
          XMT 350 CC/CV
          S74DX feeder
          Stick leads from here to China
          A30 Spool gun
          Langmuir crossfire hobby table
          Everlast powerplasma 100 w hypertherm torch
          Harris O/A
          Pet raccoon
          I'm just a peckerwood in the boonies with fancy welding equipment


          • #6
            Could be 7000 series. Welds fine but will always crack at some point later on

            Miller Trailblazer 325 efi
            Miller extreme 12vs
            Thermal arc 186 ac/dc
            Lincoln power wave 455m/stt with 10m dual feeder


            • #7
              You know, it could be magnesium as well? Just saying...? Do you know the way to tell?


              • #8
                Yup 7000 series, like AR receivers..Bob
                Bob Wright


                • #9
                  What brand is the shotgun?

                  It's too bad you boogered it all up, most firearms manufacturers will warranty stuff like that, even though they don't have to. I would find it highly unlikely for them to do so now.


                  • #10
                    And some gun receivers are Zamac...Bob
                    Bob Wright


                    • #11
                      7000 series Aluminum eh? Zinc, the major alloy element. In some respect, isn't that like saying let's weld pot metal? Not many want to attach their handle to that, me included.
                      Now I noticed in following along some sage advice has been offered up. Things to watch out for, anodizing and coatings? Things to be concerned with, heat treatment and a loss of strength? And while I understand the embarrassments one might perceive he faces in exposing a failing...he really should show these doctor's the mole.

                      This cracking could weld this till the cows come home and if adequate filler doesn't over come cooling contraction forces, it'll still crack. I have no clue to the part or it's function, but arm chairing this as someone bringing me broken and can I fix it, asking questions, doing some checking should be par for the course with some touch and feely.

                      And while some might think the power source makes the welder, I'm of the belief the welder still makes the power source look good? I'm not selling buddy short, but owning a Dynasty, reading the manual, what it means with when to use it, knowing and applying how to use it, that's like four different things?

                      I've seen magic. I've seen the effects of a slow building up of temperature to cause melting, and a slow reduction to cause solidification. I've seen the effect of voltage forces push metal, as well gas flames from the pressure settings.

                      I've seen a fellow pack moistened asbestos fibers to create a supportive mold backing under supported separate pieces of pot metal grill to then slowly bring up in temperature to melt, stir back together and allow to solidify using a small oxy acetylene flame with a magic filler rod.
                      My attempts were less then stellar. I melted that stuff.

                      What I'm wondering is, is that part unavailable? Rare? Not reproduceable? I'm not in the know that way, just curious? I've been to Fab Tech. This 3d printing technology...what can't be made?
                      Other then admitting defeat, what's a new one worth for dollar bills?
                      Anybody know?
                      Is that an extruded and machined part? Cast and machined? Not being a firearms owner, Canada and all, is this the chic, chic part?
                      Or maybe if someone would have said, JB weld, paint it black and no one will know the difference?
                      Would that have worked? Lol... just wondering?


                      • #12
                        Zamac is pot metal and it's used by a wide variety firearms manufacturers. Not sure if any shotguns are made from it, but I wouldn't doubt it.


                        • #13
                          sorry for the delay, was off work... its a BENELLI SBE2 semi auto. I had ORIGINALLY called the factroy and told them about the crack and the fact that the ID opening in the front of the receiver( right where the threads start) had WORN out so much the mag spring follower( or pusher) would shooting into the reciever when the last shell was used up. I machined several subsequently larger ID followers to alleviate this problem... but the flexing of the action with the split would allow that ID to open just enough that the SHELL would move over sideway enough to get past the catch!....ive shot about 20,000 3.5" high velocity loads and the gun just is saying uncle. The Benelli USA company told me there was NOTHING they could do to fix the gun. It was about 10 years out of warranty. but i tried to weld it and machined some new followers and got by... i revisited the welding recently, and tried the latest events I described. dont critisize my weld too much..i was trying to not overheat the whole frame, and there were impurites coming up from the threaded steal tube... s I tried to drop and ball and flow it out.... this was a third repair weld after I welded in the 1/8th insert..that weld was very nice!.....ive called the dealer I bought the gun from originally to prompt them to allow be to buy a stripped receiver.....but the cracking is still a mystery


                          • #14
                            also know that I machine down the weld to the original dimension of the gun, so the other parts fit!!..... the picture just shows the place i gave up at!


                            • #15
                              dvice...Thank you for the detailed reply. I down loaded the picture and enlarged it. I think it's weldable and fixable. My opinion.
                              I also think your getting it to hot and liquid. Like adding excess liquid in the mash potato's. Smooth and creamy lacking texture.
                              While I did notice some porosity from contamination, I'm of the opinion it's the result of excessive puddle fluidity and resulting metallurgical structure being weaker that with cooling and contraction forces, causes it to crack.

                              It could be due to arc length, higher currents, power source setting adjustments, as well contraction from the other side if that make sense? This again is my opinion.

                              I would weld small beads, less heat, tighter arc and maybe tweak the balance slightly, above all, take your time. The magic will happen fast or slow... Your rapidly boiling the potato's and you'd be better off if they simmered instead, if that makes any sense?

                              I don't see the powder burns of excessive zinc in the aluminum. I do however see a need for finer control of depositing metal. My advice, slow down, smaller deposits more frequently to rebuild it. Three or four small passes instead of one or two larger passes. Finer grain structure, stronger tougher deposits.

                              You might also add a light preheat to the back side to reduce contraction stresses before and possibly after. Just a thought and hopefully of some benefit?