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  • Question About Brazing Rod

    Sorry Mr. Bulliss. There wasn't enough action over on the welding sub-forum so I'm advertising my thread here

    I'd like to get this project started as soon as possible, so the faster I can get some advice on which rod to use, the better! Thanks guys.

    http://bbs.homeshopmachinist.net/sho...066#post589066

    Originally posted by Fasttrack
    I need to repair an old tractor exhaust manifold. Previously, when brazing, I used whatever was on hand to braze. I had no idea what alloy it was.

    Now I am looking at buying some rod and flux and was wondering what type would be the most suitable for repairing dirty cast iron. I realize I will need to do a lot of prep work before I start brazing, but I just don't know what type of rod I should buy.

    I'd really like to get some coated, low fuming bronze rod (RCuZn-C) and the associated paste flux because it's cheap! But if it won't work or if the joint won't hold up, then I will spend a little more and get some nickel or silver bearing rod.

    Thanks!
    Last edited by Fasttrack; 09-08-2010, 08:45 PM.

  • #2
    No one gave you any response so I'll just tell you what I've used. I've brazed several different exhaust manifolds getting excellent results with plain old flux-coated bronze welding rod. I get it from Airgas. I don't think it's anything special.

    With those manifolds, you can either braze them or use nickel rod...but you already know that.

    My point is, I don't think you need a special brazing rod for a manifold. What is important is the cleaning, beveling and preheating. The hotter the better as long as it's less than red hot. Someone else said that sandblasting or bead blasting the crack area is a great way to start.

    I also have some extra blue flux that comes from a can that my Dad bought in 1959 with his first O-A setup. It's still half full. LOL.

    JMO.
    Last edited by gnm109; 09-09-2010, 01:11 AM.

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    • #3
      Thanks Gnm109. That's good enough for me. I just wanted to make sure I wasn't going to purchase the completely wrong thing

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      • #4
        I too have brazed a fair number manifolds, and even blocks. Brazing holds up just fine, I repaired the manifold on my truck about ten years ago, I drove it another 130,000 before trading it in on a new truck, never had a problem. I use the same white flux coated brazing wire that Gnm109 uses. Preheat and don't allow it to cool off very fast, the slower the cooling the better, preheat 400-500F is good.

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        • #5
          After the proper prep work. I use a propane burner, like from a turkey fryer, to preheat cast iron parts. I leave the work on the burner , with the flame on, while I am Oxy-Acetylene brazing using Boric acid type flux, or just plain arc stick nickle rod. When done I reduce the heat slowly, until cool, or pack it in sand.

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          • #6
            The temperature of the casting when welding with NI rod is significantly higher than when brazing. I'm much more careful about preheating, keeping the part hot while welding, and cooling the part afterward.

            The one thing I don't want to do when brazing is get the base metal too hot.
            Any products mentioned in my posts have been endorsed by their manufacturer.

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            • #7
              Originally posted by gnm109
              Someone else said that sandblasting or bead blasting the crack area is a great way to start.

              Be careful what media you use to blast the part. From http://www.wallcolmonoy.com/techservices/brazing/basemetal.html
              "While using mechanical methods of oxide removal and cleaning, blasting with oxides such as aluminum oxide is not recommended. This will cause the nonmetallic oxide particles to embed in the base metal surface and result in loss of joint strength."

              There's some good information there if you are a bit of a neophyte at brazing.
              Location: Saskatoon, Saskatchewan, Canada

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              • #8
                I too just use the common flux coated Bronze brazing rod although I prefer the bare rods and flux, I use the flux coated rod because it is easy to get. Also I have used sand blasting for years with no problems but as pointed out the type of media can make a difference, plain silica sand (play sand) works just fine because it does not embed itself into the metal surface but if small cracks are left be sure to remove any sand that may be trapped.

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                • #9
                  I TIG cast iron using Eureka 5545 filler and I have had very good luck.
                  You asked about brazing filler and not what process to use.
                  Either bare(with the proper flux) or coated low fuming rod will work.
                  Last edited by BigMike782; 09-10-2010, 09:43 PM.

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                  • #10
                    Harris-Welco 17

                    I highly recommend Harris-Welco 17 fc flux coated brazing rod. It wets the cast iron surface better than bronze or brass. I also add additional Sta-Silv flux and have really good results.

                    The cleaning and preheat are very important as the others have said. Usually I heat the base metal until the brazing material flows.

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                    • #11
                      Originally posted by Jpfalt
                      I highly recommend Harris-Welco 17 fc flux coated brazing rod. It wets the cast iron surface better than bronze or brass. I also add additional Sta-Silv flux and have really good results.

                      The cleaning and preheat are very important as the others have said. Usually I heat the base metal until the brazing material flows.

                      I like the way that rod welds (brazes) also but when you posted that I was all ready to point out that it would not be nearly strong enough for that manifold, I decided to check the specs first to get the exact numbers and I am sure glad I did! The tensile strength at 80,000 to 85,000 is much higher than I thought, not sure where I got the idea that this was a low tensile material but that is what I have mistakenly thought and I have passed on using it several times for that reason.

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                      • #12
                        Originally posted by radkins
                        I like the way that rod welds (brazes) also but when you posted that I was all ready to point out that it would not be nearly strong enough for that manifold, I decided to check the specs first to get the exact numbers and I am sure glad I did! The tensile strength at 80,000 to 85,000 is much higher than I thought, not sure where I got the idea that this was a low tensile material but that is what I have mistakenly thought and I have passed on using it several times for that reason.

                        As I said earlier, I've done five or six car manifolds and a few other cast iron pieces with braze. I just used the ordinary flux cored brass with an occasional dip into my vintage blue flux can. It's all good.

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