welding a fireplace grate?

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  1. diymirage

    diymirage HP@idle > hondaHP@redline

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    hey guys
    i got a nice big fire pit outside, and i picked up a few grates for a last year
    i got both of the grates butted up against each other, which creates a high spot in the center

    so thought it would work better if there wasnt a high spot, so i thought i might cut the backs of both of em, and weld them together

    now, im pretty sure these are cast iron grates, and all i got is a fluxcore welder
    ive been told this may not work because cast iron likes to get brittle when hot, but these are grates made to get hot, so who knows
     
  2. jack68gts

    jack68gts Well-Known Member

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    it can be done,,its easier with a stick welder and high nickel rods, but it can be done with flux core, just wont be pretty,,but if its a firepit, it wont matter. turn your welder up, and also preheat the joint,,if you use 25/75, turn the pressure down.
     
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    • moparmandan

      moparmandan FABO Gold Member FABO Gold Member

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      I've always been told and seen it work, that if you heat cast iron up first you can weld it. Throw that sucker in the fire get it cherry hot, then weld. LOL

      Hopefully the professionals will chime in.
       
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      • brian6pac

        brian6pac Well-Known Member

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        I always preheat and post heat and use nickle rod and it will work fine
         
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        • harrisonm

          harrisonm Well-Known Member

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          I have been MIG welding for a long time. I had always heard that you can't weld Cast Iron. A while back I saw a welding segment on a car show on TV. They showed that with a MIG welder, the weld will sort-of stick, but you don't get the same 'Bond' you get with MIG welding steel. They heated the area up with a torch and then used a high nickel content rod.
           
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          • famous bob

            famous bob mopar misfit

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            I have never seen a cast iron grate my self, but welded some old seatbelt bolts for support legs on an old grate that was about burned up and sagging. It lasted about 10 more yrs, or so------stick welded.
             
          • 1973Barracuda

            1973Barracuda Well-Known Member

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            You can preheat and braze as well. Saw it done on a manifold years ago.
             
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            • Tooljunkie

              Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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              I broke my manifold on my kubota. While engine was still hot i welded it back on. Ground a vee and went to town with the mig. I started tractor while it was still hot and its still fine.
              Not pretty.
              Propane is hot enough for pre-post heat.
              Weld a couple bolts across the joints, may give it some strength.
              Whats the worst that could happen?
              Have welded a few cast pieces, sometimes a couple attempts to get it to hold.
               
            • Dana

              Dana FABO Vendor FABO Vendor

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              Post heat is just as important. Cast should be around 400f preheat, then cool in vermiculite, sand or wrap it in ceramic blanket. If you have a buddy that can be ready with a torch as soon as you get done welding would be "grate" pun intended. That thin piece will lose heat quickly and start to spiderweb crack.
               
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              • Dartnut

                Dartnut Don't hate me because i'm beautiful

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                Here's my 2 cents.
                I would do all of your joint prep and grinding off paint etc. first.
                Then i would start the fire up and get it going good.
                Set the grates on there and let them warm up to a dull cherry red.
                Have your table or bricks set as up close to the fire as possible as well as your welder.
                Weld using Ni-Rod or stainless about 1/2'' at a time starting with the ends and middle.
                Put back on the fire immediately, and reheat.
                Do this until you are satisfied with the strength that you require.
                Leave welded grate on the fire until it burns out and the hot coals will keep it warm for hours and let them slowly cool the part.
                Don't expect the welds to be pretty, the quality of the cast iron that they use for grates is low and there maybe voids of carbon etc. in the casting itself.
                After it is completely cooled off overnight, then you can clean up the welds, paint, etc.
                Then you're done!
                 
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                • 1973Barracuda

                  1973Barracuda Well-Known Member

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                  Totally agree with the post heat. The guy I watched do it, used an oxyacetylene torch to do this, lots of patience to preheat, a larger area, not just where he was brazing. He would braze, reheat, braze, reheat a bigger area than just the braze. When complete, he still kept a good size area warm for a bit. I think a fire would work for the post heat.
                  In a previous life I was a metalworker.
                   
                • diymirage

                  diymirage HP@idle > hondaHP@redline

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                  I wonder if I can mate it some other way
                  (I just don't have the tools to pre and post hear it properly)
                   
                • Princess Valiant

                  Princess Valiant Duster specialist

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                  Dang, that sounds like a fun project, I wish I were closer to help make an attempt.

                  I would just try it with the resources you have available, the worst that will happen is it might fall apart but it will be interesting to see how it plays out
                   
                • moparmandan

                  moparmandan FABO Gold Member FABO Gold Member

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                  Come on let's see some pics! You should be toasting marshmallows by now.
                   
                • diymirage

                  diymirage HP@idle > hondaHP@redline

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                  once the baby goes down for a nap, ill swing out and grab some pictures, show you guys what i have in mind...i might just be able to cut, drill and bolt it together
                   
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