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welding cast iron

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  • welding cast iron

    I have a transmission case off an old John Deere tractor that is cracked that I am planning on welding. It is to large to put in my oven, 3' X 2', to preheat. I have welded cast iron before with good results with my mig welder but have always been able to preheat. Do any of you know of any welding sites I could get information on the best method to do this. thanks Bets

  • #2
    No websites,but you can use the method I use,cut a steel drum in half but the case inside and fill to the top heaping over with charcoal and lite it off,maybe give it a little air from a regulated shop air hose to get the charcoal really cooking,after the heap of charcoal on top is burned down level with the case begin welding,after welding heap on fresh charcoal and let burn till tommorow.Works good for me,especially the long cool down.
    I just need one more tool,just one!


    • #3
      Betts, I have had good results Arc welding with Ny-rod. (nickle base). Just grind out the crack untill you see daylite and weld away. No preheating. Hold a long arc and it lays in there pretty good. I have repaired frozen water pumps, Air compessor heads, even a bale fork from a square baler. this system works best if there is no stress on the weld area, But I have welded a cast iron cylinder liner on a motorcycle. still running. Luck, Doug


      • #4
        Here is a web site with some information.

        I have fixed some broken castings using 309L.
        Its not always successful,,, preheat, peening and postheat and slow cooldown are necessary.

        good luck


        • #5
          check out these guys:

          I had them repair the block in a car that I restored a couple years ago. They repair broken iron, finish the welded surface to look like an as-cast surface and guarantee the job. Not cheap but good. Suitable for the best of show cars.


          • #6
            I will second the Ny-Rod suggestion. I always preheat, peen and cool down slowly. 99% nickle is the best IMHO.
            To invent, you need a good imagination - and a pile of junk. Thomas A. Edison


            • #7
              I have doubts about the use of MIG for welding cast iron also. I have always had good luck with nickel alloys intended for cast or 309L, which has a high nickel content. Preheat, peen and slow cooldown are method to follow.
              Mild steel welding rod or MIG wire may fuse in the weld area and appear to be sound, but will usually fail. The failure usually is in the area just past the actual weld.
              The most common repair for cast iron is brazing. It is strong enough for most applications, easier for the home shop, and usually does not require as much preparation. Vee the repair well, preheat the area with the torch and braze. Slow cooldown is recommended also.
              Jim H.


              • #8
                I have used Nickel rods on a DC welder to weld cast and have had no problems, same methods as above but drilled small holes at each end of the cracks to keep the cracks from spreading during pre-heat. I don't know if the holes are necessary but that is the way I was shown.


                • #9
                  I third the nickle rod. No preheat. Stitch weld and peen. Let cool. go to opposite end and stich and peen, let cool. It takes awhile, but has always worked for me.


                  • #10
                    I drill ends of crack preheat, weld with mig, wrap up in cerwool to cool slowly. There are lots of exhaust manifolds running around done like this. You commonly have to redirect the exhaust dumps to clear a new frame.

                    Brazing is a good option too.

                    last one I did, I was drinking, I did it with stainless mig wire and straight Argon.

                    Still holding..



                    • #11
                      Brazing works nice on cast iron. Just don't expect it to work on an exhaust manifold. I'm sure you know that ibewgypsie. Just the way you worded your reply made it sound like you could.

                      Super Dave
                      Super Dave


                      • #12
                        The Lincoln welding book has a procedure for welding cast iron if you can get a copy. There is both a cold and hot procedure. The hot procedure requires keeping the metal temperature at 400F to 600F throughout during the welding and then letting it cool down slowly.

                        The cold procedure goes like this:

                        * clean rust, paint, etc. thoroughly
                        * determine both ends of crack by using dye penetrant
                        * drill both ends of crack
                        * grind both sides of crack to form V - - DO NOT USE aluminum Oxide grinding disc - - use silicone carbide ( I use carbide grinding bits)
                        * if crack is long grind a V perpendicular to crack about 1" long at 2" intervals
                        * skip weld depositing no more than 1.5" at a time
                        * peen after each weld
                        * allow the metal to cool down until you can easily hold your hand on the metal before laying down another weld

                        A "Ni Rod 99" is recommended. It is mostly nickle and used DC reverse polarity. It is also very expensive!

                        I have used this procedure several times on cast iron in high stress/critical locations including a large compressor head and a piano plate. So far they have all been successful. I have also done this with a TIG welder and find that I can see what I am doing much better with that setup.

                        It is slow but it has worked for me.

                        Ordinary steel electrodes including MIG wire will work sometimes but can also just pull out of the base cast iron sometimes. The procedure above is for critical areas and they say in the preface that even if you follow the procedure it is not always successful.

                        Good luck,


                        • #13
                          I don't claim to be an expert on welding at all, but I have welded cast-iron on a few occasions. On items with zero STRESS, I have gotten away with MIG welding using standard steel wire and in Aragon CO2 mixture. This worked extremely well fixing a broken piece of the exhaust manifold on my 320i years back. It also kind of worked for fixing a small high pressure pump housing, it held together fine in that application, but there were several small cracks that leaked like hell.

                          If you want to use a MIG welder, you need to do some research. Back in the eighties I had some important thing which needed to be welded, and which was cast-iron. A Millermatic 200 was my only choice for welders. After a great deal of research, I found out there was a special flux-core welding wire available just for welding cast-iron. It contained a very high percentage of nickel, and a 10 pound spool was about $200. It also required a special three gas mixture, I believe one of the gases was something like 5% oxygen. Ended up not welding the thing at all.

                          For the application you are doing, I believe strength may be important. I would either use the nickel rod that has been recommended, or try to find out what the wire that I had lined up was. Brazing is also not a bad idea. For what it's worth, I have never seen a cast-iron weld which I was truly 100% pleased with. And I have seen more than one weld were part was preheated, proper nickel rod was used, and the part was cool slowly. And you could still break it apart with your bare hands when it was all done :-( getting a used transmission case might actually be a better and cheaper solution for you in the long run, if that is not possible and this is something you really care about, you may be better off paying somebody who does this on a regular basis. Did I really say that?