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Would you trust this weldment?

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  • Would you trust this weldment?

    Don't think I would......

  • #2
    Sometimes ya gotta do what ya gotta do. Part might be unobtanium on a machine that's otherwise worth
    fixing. Lots of reasons to fix it, lots of reasons not to. Might be a temporary repair while waiting for a new
    part to come in. I've done a few repairs on parts that were broken as bad or worse than that Welding cast
    iron is always "iffy" but with a little patience and care they can be fixed pretty good...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

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    • #3
      Not without preheating it. I would have brazed it.

      I hired out a large(ish) casting repair last year. Frame for a set of rolls. My guys do miles of mig weld, but there might not be 10 hours of cast iron experience between the lot them. So it did not make sense to F'around and learn on this piece of production machinery; it needed to get fixed once. The group that did it only does cast iron repair and travels extensively. Some piece breaks in a mine 500 miles away, that's what they're doing next week. Specialists with lots of experience. Anyway, if the crack is less critical, like a housing or guard, they'll metal stitch, but if structurally critical like a roller frame they want to braze it not weld it. They claim its every bit as strong, doesn't need the same level of preheat and overall has a much lower chance of something going wrong
      in Toronto Ontario - where are you?

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      • #4
        Originally posted by Mcgyver View Post
        Not without preheating it. I would have brazed it.
        I agree that brazing is the preferred method for repairing cast iron but did you see that casting? Brazing is every bit as strong as welding if you maintain the proper clearances but there's no way to fill in the kind of holes shown with normal brazing techniques. I've read about wide gap brazing where you pack the gap with powdered base metal (in this case it would be powdered cast iron) that acts as a sort of matrix for the braze material to flow around / through. I guess that would work and maybe that's how the specialists would do it. If I was faced with a casting as shown, I'd probably (reluctantly) reach for the welder and hope for the best!

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        • #5
          There is a technique illustrated in Lincolns Handbook of Arc Welding, in which machine castings are repaired by embedding steel studs into large cracks, followed by the usual precautions of welding cast iron. They illustrate a large press frame being repaired in this way.

          I've repaired castings both ways, and it can work OK either way if it is done right. And thats a big "if".

          You can braze with regular brazing rod and a big enough torch. I think it would be OK to use a mild steel filler in large cracks. And as always, post-heat with insulation.

          For actual weld repairs -- Where possible I use pre-heat and post-heat with slow cooling under insulation. I prefer to "butter" the surface with a few layers of nickel rod, to mitigate the issues of carbon migration and precipitation cracking. Maintaining the pre-heat between passes, I then switch over to regular old 7018 to complete the repair. Never let the casting go much over 800F overall. I've never had a failure in this way. Keep the slow cooling in mind, or use post-heat and insulation.
          25 miles north of Buffalo NY, USA

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          • #6
            Originally posted by nickel-city-fab View Post
            There is a technique illustrated in Lincolns Handbook of Arc Welding, in which machine castings are repaired by embedding steel studs into large cracks, followed by the usual precautions of welding cast iron. They illustrate a large press frame being repaired in this way.

            I've repaired castings both ways, and it can work OK either way if it is done right. And thats a big "if".

            You can braze with regular brazing rod and a big enough torch. I think it would be OK to use a mild steel filler in large cracks. And as always, post-heat with insulation.

            For actual weld repairs -- Where possible I use pre-heat and post-heat with slow cooling under insulation. I prefer to "butter" the surface with a few layers of nickel rod, to mitigate the issues of carbon migration and precipitation cracking. Maintaining the pre-heat between passes, I then switch over to regular old 7018 to complete the repair. Never let the casting go much over 800F overall. I've never had a failure in this way. Keep the slow cooling in mind, or use post-heat and insulation.
            Now there's a Nickel's worth!
            Thanks to all. I would like to see what this part looks like after a year in service. I have my doubts.

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            • #7
              Originally posted by nickel-city-fab View Post
              I prefer to "butter" the surface with a few layers of nickel rod, to mitigate the issues of carbon migration and precipitation cracking. Maintaining the pre-heat between passes, I then switch over to regular old 7018 to complete the repair. .
              I understand the "butter" with nickel but why do you switch to 7018? Cost of nickel or some other reason?

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              • #8
                Originally posted by strokersix View Post

                I understand the "butter" with nickel but why do you switch to 7018? Cost of nickel or some other reason?
                Yes, mostly cost. The two rods have almost the same strength, basically, but once the nickel has done its job there is no reason to keep using it. On smaller repairs the whole job is nickel, but on the bigger repairs where you are using dozens and hundreds of rods, you only need that first few layers.
                25 miles north of Buffalo NY, USA

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                • #9
                  Originally posted by Fasttrack View Post

                  I agree that brazing is the preferred method for repairing cast iron but did you see that casting? Brazing is every bit as strong as welding if you maintain the proper clearances but there's no way to fill in the kind of holes shown with normal brazing techniques. I've read about wide gap brazing where you pack the gap with powdered base metal (in this case it would be powdered cast iron) that acts as a sort of matrix for the braze material to flow around / through. I guess that would work and maybe that's how the specialists would do it. If I was faced with a casting as shown, I'd probably (reluctantly) reach for the welder and hope for the best!
                  You're right on the size of the crack, I just skimmed through the video, but there didn't seem to be much about preheating or cooling. Was more passing along that I spent bit of time with some people that that's all they do. Never say never I guess, but the message I got was we don't weld CI, there is no reason to and its more problematic. Those missing bits might be a reason, no idea how'd they would tackle that job. Likely its hypothetical...they're very expensive (a business opportunity?) so probably not the sensible route if you find some old thing in a barn with missing pieces.
                  Last edited by Mcgyver; 08-14-2022, 06:06 AM.
                  in Toronto Ontario - where are you?

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                  • #10
                    Man, I hope this guy's insurance company isn't watching- nothing says 'Safety' like welding next to a stack of plywood.

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