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can i silver solder cast iron ????

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  • can i silver solder cast iron ????

    I repair old phonographs for the hobby, and stuped me I brook a part and I need to fix it . So can you silver solder it and what type do I use.

  • #2
    Yes. I use the "hard' silver solder so its more like brazing. But yes. JR

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    • #3
      This is not the one I was thinking of. It will also work but the type I also have comes in 18" sticks like brazing rod. I cant find it in this heap JR



      I have this kind also but I think its more for electrical work. Never used it so dont know too much about it. JR

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      • #4
        Yes you can Brett.
        There are two silver solders ( More actually, but not here for the moment) High Temp and Low temp

        The high temp melts at 1145 F. and contains 45 % Silver ( which is superb for wetting surfaces) and the first photo shows a sample of that. It requires a propane or Mapp Torch and some Borax Flux.
        It is extremely strong and if the joint is .001" thick , will be stronger than the metal it is binding.

        The second photo shows a low temp solder. and it has maybe 2 % Silver and melts in the vicinity of 380 F ( as I recall) . It can be used with a Iron or oven to heat the metal , but it requires a acid Flux , like Hydrochloric. If you buy this, get the stuff called "Stay Brite" as it comes with the proper Flux.
        The Low temp does not have the strength as does the High temp as it has Lead in it I believe. I have used both and if the part has not a lot of stress, the low temp should work fine.
        Rich

        PS The thinner the joint, the stronger the bond !
        Also note the words " Silver bearing", that denotes a low percentage of silver ...like 2 % or less
        Last edited by Rich Carlstedt; 02-27-2018, 08:05 PM.
        Green Bay, WI

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        • #5
          Why silver solder brazing is better. There are brazing alloys that contain silver that wet, flow and penetrate better than regular brazing alloys but these are not really necessary except for special applications. Talk to a welding retailer and see what is available.
          The shortest distance between two points is a circle of infinite diameter.

          Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

          Southwestern Ontario. Canada

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          • #6
            The key is patience. You want to get the whole part up to temperature before applying the silver solder. You also don't want it too hot. When the part temperature is correct the repair will be a thing of beauty. When it isn't you will be disappointed.

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            • #7
              Yes, and you can even soft solder it. I did that to attach a new wear surface to a shaper crank block. It worked fine, still in there.
              2730

              Keep eye on ball.
              Hashim Khan

              Everything not impossible is compulsory

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              • #8
                Straining at gnats and swallowing camels department, antiques restoration bureau, gratification of OCD fuss-budgets section:

                Cast iron can be difficult to wet with brazing alloys. I've always thought the problem was surface carbon - nothing wets it except grease. My favorite trick was to fine media blast the fracture faces just before brazing. The media has to be clean - that is, uncontaminated with corrosion and paint residues - and the air dry. You don't have to over-do it, just blast off the carbon until the surface looks dull light gray, almost white. The surface contour is preserved, the fractured surface will still self-key into position. Flux, jig, heat and braze immediately. Makes a strong joint that requires little dressing to make an almost invisible repair.
                Last edited by Forrest Addy; 02-28-2018, 01:57 AM.

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                • #9
                  What I did was to heat the block up quite hot several times. Never to red heat, but plenty hot. When it stopped smoking while hot, I was able to get solder to wet it.
                  2730

                  Keep eye on ball.
                  Hashim Khan

                  Everything not impossible is compulsory

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                  • #10
                    Brett,

                    No idea what equipment you have, or how much of this sort of thing you need to do. But one more possible option; silicone bronze wire is available for MIG welders, which apparently can be used on cast iron. The wire has a lower melting point than the cast iron, so it's brazing rather than welding. It can also be used for joining dissimilar metals (not relevant in your case, but...).

                    I think you'll need to pre-heat both parts for this to work; good luck!

                    Ian
                    All of the gear, no idea...

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                    • #11
                      Originally posted by J Tiers View Post
                      What I did was to heat the block up quite hot several times. Never to red heat, but plenty hot. When it stopped smoking while hot, I was able to get solder to wet it.
                      Maybe it does the same trick as Forrest's "sand"blasting. Free carbon or graphite on the surface will burn off when heated above ~450 cel and given sufficient time.
                      Location: Helsinki, Finland, Europe

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                      • #12
                        you guys are wicked smart thanks for the info I will get a piece of cast iron and the silver solder and practice frist, thanks Brett

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                        • #13
                          Its certainly what you need to do if its an old fracture and is greasy. Heating it burns the oil out.
                          'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                          • #14
                            Brett,
                            I would be interested to see a photo of the broken part.
                            Thanks

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                            • #15
                              A word of caution if you ever decide to use the low temperature Stay-Brite solder kit, DON'T. At least not in a shop that contains any steel you do not want to rust. That flux migrates and the next day or so you will find a coat of rust on anything made of steel within 10 feet of where you did the soldering. I no longer allow it in my shop.

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