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Mig welding

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  • Mig welding

    Hi: I restore old Gravely two wheeled tractors. Numerous times the exhaust ears are broken on the manifold and sometime the holes in the block
    are broken out. I am using a miller 210 with ER70S3 wire to fill the holes in, and to build up the exhaust ears. The spark test has lead me to believe that the block is made of cast steel. The sparks come off bright orange and not the dull red that would indicate cast iron. Sometimes the weld is so hard, that I can not drill and tap it: This happend tonight. Last night I filled in one hole and had no prblem drilling and tapping it. The heat setting has been the same: #3. Is there a mig wire out there that more readily lends itself to drilling and tapping. Should I pre-heat first and then heat after to slow down the cooling. Before I started I took some 1" round and drilled i hole in it. I then filled the hole with the ER70S3 mig wire and had no problem drilling and tapping it. I am confused on what is occuring. thanks gene

  • #2
    No, that is not the right wire, some type of nickel would be the ticket. The common steel you weld with and the common mig wire are very similar mainly in carbon content. The cast is very high carbon and when you make this weld it mixes and makes it brittle and hard to varying degrees depending on technique and mix, etc. Thats kind of a rudimentary version I supose. Obviously you made a deposit harder than the drill bit.


    • #3
      You should be using carbon plugs to save the holes before welding them. I bet Franz could help you out if you went over to the toolboxtalk forums. He's probably got one of those things in his shed.
      Syncrowave 250DX
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      • #4
        you may want to try carbide drill bits and powder metal taps. But be aware they are expensive.
        Trailblazer 302g
        super s-32p
        you can never know enough


        • #5
          If he is using mild steel wire on cast the results would be unpredictable at best and could very across the whole hardness range throughout the whole weld or any part of it. Probably some machineable nickel and the right amount of preheat, slow cool would make it do-able. My Bud made some steel clamps with bolts for something like that and it worked well, for threaded hole repairs inserts work. Often with a broken cast ear I dont try to repair it conventionally, I might grind it to fit and weld a structural nut in place with nickel, comes with new threads. I have even done case damage repair with JB Weld and patches on occassion.


          • #6
            Some 2# flux core nickel would be a great product line for Hobart?