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Aluminum welding questions, and one SS/TI question

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  • Aluminum welding questions, and one SS/TI question

    I'm familiar with the general GTAW theory on aluminum.

    I do have two questions:

    1) With OA welding on aluminum, the flame/gas creates a zone of protection similar to what you get with the gas when GTAW welding aluminum. It would seem impossible to ensure that what with spot welds, and interruptions in the work, that the weld had never cooled out of the gas (no post flow), or you never cut into a section that had already been welded, and would have some oxide on it. Why is it fine to weld this way, but you can only GTAW aluminum with an AC current (usually pretty sophisticated AC)? How does OA de-oxidize the join as you work along? Why is OA considered good, but DC GTAW on Al doesn't work.

    2) Someone once mentioned they used to sell Al stick electrodes. What is the story on that? How well or badly did they work?

    3) When forge-welding steels, including SS, you can get real good results. The means of keeping your surfaces clean relative to weld quality is to use a reducing flame, and a flux. When DC GTAWing on SS or maybe even TI, the recommended strategy is to backpurge the weld area, or even in some cases weld in a sealed cabinet. Is it ever possible to use a flux to protect the joint? Let's say you have a well fitted joint, and it at the borderline of needing purging, are there any fluxes that could be used to preserve the joint integrity while doing GTAW.

    I'm just curious about this stuff, I'm not trying to rewrite the book on nuclear sub welding. Sometimes there are fixes out there that might help redneck engineering. In some cases they may have been standard practice until they were superceded with more modern methods.

  • #2

    1 You cant OA weld aluminum. However, you can OH weld aluminum. (oxy-Hydrogen) You can DC weld Aluminum with the GTA process, in either a straight or reverse polarity. In straight polartiy, it is important to weld at a much higher arc voltage, in order to pierce the oxide. This can be done through different gases or the use of a plasma column.

    2 Yes they work, in emergencies

    3 Many fluxes are avaliable for tig welding. None work as well as back purging. One company makes a flux that will triple you penetration without growing your HAZ.

    Anything is possible in welding, you just need to open your mind.


    • #3
      According to "Getting an A in Aluminum" by Kent Caveny, aluminum can be welded with OA.
      Using his method, a water soluble flux is brushed on and heated gently with the flame to evaporate the water. The flux cleans off the oxide layer just as the AC would. After the weld is complete, you must be careful to wash off all the corrosive and toxic flux to prevent damage to the part, to your tools, and to your health.
      He does seem to hint that welding with OA requires a lot of skill and a properly set-up torch.

      The book is preparation for welding body panels for hot rods, so the procedures discussed are only for .060" thick 3003H14 aluminum.

      I think the biggest problem with OA welding aluminum is that you just can't get enough heat into a small enough flame, so GTA/SPEC may still be correct that you can't weld thicker aluminum with OA.


      • #4
        GTA all the aluminum I've ever seen welded was done AC with high frequency,
        I would like to see some DC for comparison.



        • #5
          Thanks for all those great points.

          I saw this article where a guy was saying that the OH was specified for aircraft aluminum, only because Acetalyne was reserved for the shipyards during the war.

          Any particular brand for aluminum electrodes?


          • #6
            Henrob makes a torch that will OA weld aluminium very well.. Dip a aluminium 4043 tig rod in Wilco Harris #10 flux and that torch will weld very similar to a tig set up but the torch is OA & no electricty or gas I have the torch and it cuts like no OA I have ever used (percise) & uses 80 percent less gas (4psi acetolene & 4 psi oxygen on 3/8 steel and non ferrous metal) Have not had much time to practice on welding but looks very promising.


            • #7
              I believe that DC TIG on aluminum is reserved for fairly thick weldments that require A LOT of heat input. I read up on it some time ago and realized that it didn't have much application in the mainstream. I'd like to know if those in the trade have actually used it and in what situations. JEFF
              200DX 350P 625 Plasma & other stuff I forgot


              • #8
                dc welding alum

                I have done it in work just to see how well it goes.I prefer to tig weld it in ac mode. On occasion I build pressure boxes for molds for the plastics industry(steel or alum).But I definatley like to do all my alum work in ac.I found dc welding alum you have to crank it up for it to work well.THE RESULTS I HAD FROM DC WELDING WERE GOOD AS FAR AS I WAS CONCERNED BUT IT COULD HAVE BEEN PRETTIER IN THE AC MODE. I WOULDNT WANT TO USED IT ON THIN STUFF FOR SURE. PENETRATION WAS MY MAIN CONCERN THEN AIR TIGHT BUT IT WORKED OUT WELL BUT ILL STICK TO AC UNLESS THERE IS A REASON NOT TO. BTW I did a lot oF oa work with propellers at H&H Propeller for 12 yrs I oa'd bronze propellers and tig'd alum,st,sst,and nibral,OXY/ACET BRAZING/WELDING WAS A LOT OF FUN I THOUGHT BUT THE BLUE FLUX WAS MURDER.I HAD TO EAT A ROLL OF ROLLAIDS EVERY DAY TO KEEP FROM GETTING THE FLUX FLU. THAT STUFF IS BRUTAL.
                Brass Monkey


                • #9
                  You can Oxy-Hy weld aluminum, with no flux. This method was used to weld aircraft fuel tanks in the 30s and 40s

                  i will snap some pics, also if you have seen AC tig welds from an inverter, then you have seen it done with out HF Continuous

                  ive used harris

                  It cuts steel, it will only melt and blow away non ferrous material

                  jeffscarstrucks & Brass Monkey
                  When i weld aluminum with DC, I never use more than 180 amps. That current coupled with 24v across the arc is over 4kW/s of heat input. The corona coming off of a .093 dia tungsten and an arc length of .060 is more than enough to weld any thickness of aluminum. Last week i showed a customer how to weld billit section of aluminum together in half the time than it took with his Aerowave - running wide open. He gets $110 per weldment and it was taking him one hour per part. Now he can do 2 parts per hr. The customer cant tell the difference. Neither can 90% of the seasoned tig welders that i know. Let me snap some pics, you will see.


                  • #10
                    GTA, Thanks for the reply; that is an interesting aproach that I've only read about in the past. I would love to see some pics if you get a chance! Thanks again, JEFF
                    200DX 350P 625 Plasma & other stuff I forgot


                    • #11
                      Originally posted by pjseaman
                      GTA all the aluminum I've ever seen welded was done AC with high frequency,
                      I would like to see some DC for comparison.


                      The cheapest way to accomplish DC GTAW of AL is using DCSP with 100 helium. Make sure you Al is mechanically and chemically cleaned prior to welding. Use a good sharpened tungsten. It takes considerably more heat and patience than does AC GTAW. Try some 1/8" Al at 200 amps with the He shielding gas. Your D200DX will start well with pure helium. Good luck.


                      • #12
                        thats kinda odd HAWK. i tried it just for ****s&grins. 1.2" 6061, about 1/2" from the edge, argon. it melted it almost like butter, seemed to me that dc aluminum would need less power. what am i missing ? the metal was not very clean, so it looked REALLY crappy. but it melted it EASY. 1/4" penetration easy


                        • #13
                          Blown S-10,

                          Never had any luck with dirty Al on DC. It is bad enough to to clean well on AC. Cleaning is a necessity here. An abrasive cleaning followed by a chemical cleaning is a good start. Don't wait too long to weld after cleaning. I have always used He. Never tried Ar.

                          BTW: Read closely the posts by GTA on out of the ordinary stuff. He is not going to tell you how to straight out, but there is some good info in his posts. Remember an open mind to new techniques is worth a lot when the time comes.


                          • #14
                            That right Hawk, hope to have some pics later today.


                            • #15
                              Here are the pics.
                              Both are fillets on .700 thick material, 6061-t6, .093 4043 filler, componets were at room temp prior to weld, 55 deg f,
                              I sliced the weldments in a cold saw, then faced them with a fly cutter on a mill. I dont have the facilities to polish, but you can still see the penetration.

                              First, image002
                              AC, 120 hz, 75% bal, 100% Argon, .125 2% Ceria Tung, 300 amps

                              Second, image003
                              DC, 100% Ultra High Purity Helium, .093 2% Ceria Tung, 180 amps
                              Attached Files