O/A technique 4 building up bronze when brazing?

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I'm pretty good with basic brazing technique using an O/A torch, brazing rod, and flux. What I want to learn how to do is build up a greater mass of bronze (or "brass") when I want to, when making a joint.  Usually I'm joining steel parts - but could be stainless to mild steel, high-carbon to mild steel, etc.  So brazing rather than welding.I want to be able to build up a hefty joint sometimes... maybe a real wad that I can later shape by grinding down a bit, if need be.  One aspect seems to be to use a larger-diameter rod.  But my real problem seems to be that after I've laid down the basic joint, I'm melting the joint bronze as I try to add more material from the rod. Because, at that point, both the parent metal (being bronze) and the rod (being the same stuff) melt at the same temp. The bronze in the joint seems to liquify too readily, and just runs.I could bumble around and eventually learn the technique for this on my own, but I thought a few hints from the more experienced might make the process less painful and time-consuming. Thanks.
Reply:You may be fighting a losing battle with that. Just from what I have learned recently with brazing, and from what I know for sure with soldering, they can't be built up. There is virtually no paste range (temperature range) that allows for building up filler. It's all or nothing the first time. Desoldering can be done, as I assume debrazing can be done also. With fusion, everything freezes fast enough, but that is different.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Hi Joel_BCYou lay the rod end down on the brass or bronze, with the torch aimed at the rod end you will feel it "stick". You then push the rod and it will "stick" again, you then move to the front of the stuck rod and do it again, etc.No flux is needed with brass on brass, or red brass, I'm not sure about bronze.When you are done the bead shape will be similar to aluminum TIG.You can weld brass with a smaller tip than is needed for the original brazing.Matt
Reply:Bronze is "built-up" all the time in repair work, and in fillet bronze welding. Its all in heat control, and making sure the filler melts just before the base brazing material. Add in a little dab and get the heck out. Once you actually get better at it you can run entire beads to build up parts like gear teeth or a broken off mounting boss. It all part of actually becoming skilled at an art. Heck a couple days ago I built up a broken ear on a machine tool in our lab at work, it was only about an inch high, a quarter inch wide or so, and had a hole in it parallel to the body of the casting. Set the torch to oxidizing, tin the casting surface, set the torch to neutral, build up the missing ear, touch it up with a sanding disk, touch up the hole ( 1/2 iron 1/2 bronze ) with a drill and re-tap. The beauty of it is that youj can build up and shape a surface so accurately, little finishing machining is needed.
Reply:Originally Posted by Joel_BCI'm pretty good with basic brazing technique using an O/A torch, brazing rod, and flux. What I want to learn how to do is build up a greater mass of bronze (or "brass") when I want to, when making a joint.  Usually I'm joining steel parts - but could be stainless to mild steel, high-carbon to mild steel, etc.  So brazing rather than welding.I want to be able to build up a hefty joint sometimes... maybe a real wad that I can later shape by grinding down a bit, if need be.  One aspect seems to be to use a larger-diameter rod.  But my real problem seems to be that after I've laid down the basic joint, I'm melting the joint bronze as I try to add more material from the rod. Because, at that point, both the parent metal (being bronze) and the rod (being the same stuff) melt at the same temp. The bronze in the joint seems to liquify too readily, and just runs.I could bumble around and eventually learn the technique for this on my own, but I thought a few hints from the more experienced might make the process less painful and time-consuming. Thanks.
Reply:makoman 1860 We must have been typig at same time. Bronze for repairs is quick and easy.Peter
Reply:Peter, Yes it is  Probably why it has retained such popularity on castings for the last 100 years or so. Everyone has a little different technique, they all seem to suit just fine. I have never done much if any electic welding on castings, and my only experience that process is cutting out a previous failed repair and O/A welding or brazing it.  Interesting point, in my older texts, they specificly seperate brazing, and bronze welding. Brazing using surface area, lap type joints and no real fillet, and bronze welding using a fillet for strength. Same materials, different technique, different result.
Reply:Thanks, fellas. I do appreciate the detail you offered.  This will give me a way to practice with a bit more knowledge.The rest of it is "practice, practice, practice" as they say.
Reply:Going to a smaller torch tip during the build up helps.  It keeps it more localized.  Often times, you can get more of a controlled drip than a puddle.  As long as you reduce the heat input, it's really not that bad.
Reply:Originally Posted by makoman1860 Set the torch to oxidizing, tin the casting surface, set the torch to neutral, build up the missing ear, .
Reply:Well here is the very short version of an answerOxidizing flame-Used mainly to "tin" cast iron when brazing, excess oxygen consumes carbon and graphite on the surface of the cast base metalNeutral flame-Welding Steels, aluminum, cast iron, copper, brass, bronze, lead, and brazing cast iron and steel.1x reducing flame- Welding stainless, inconel, monel, aluminum and magnesium2x reducing flame- some ultra thin aluminum welding, heavily corroded steel sheet.3x reducing flame-applying stellite facings, and welding using the Linde high speed steel process for pipe welding. Also used for brazing and soldering aluminumThere is a lot more to it, and more specifics, but that is the crib note short version.
Reply:Originally Posted by paulinkansasWhat is the purpose of having an oxidizing flame and a neutral flame, and when would a person use those flames?  Also, in what situations would a carburizing flame be used?
Reply:Originally Posted by Matt_MaguireOxidizing (fuel lean) will focus the flame to a small point close to the tip (backfire prone).Neutral will have a brite cone near the tip and little or no feather outside the cone.Carburizing (2x cone size feather and larger) is fuel rich and broadens the heat as some outside air is needed to complete the fuel burn.I'm sure pictures are out there via Google with various explainations.Matt
Reply:makoman I agree with your short list, or at least that is what you'll find in most publications. But when brazing cast iron- if I'm having bubbles in the puddle I will try a slight carburizing flame. Most of the time the bubbles (porosity) will disappear. If I machine a bead that was bubbling while welding it will be porous after cooling. I know this is against the "grain" of most publications, but it works for me. Try it you might like it.Peter
Reply:I've found the same trick works for me castweld. Just an ever so slight feather around the cone can make a world of difference. My world war 2 welding manual actually describes a neutral flame as having a few whiskers of the feather around the cone.
Reply:You have to master your heat better, it looks like you may be one tip to large and your melting away what you lay down.I remember when I first started as an apprentice, I had similiar trouble, I asked a journeyman what I was doing wrong and he was not open about training, went for first year and they straightened all that out.Their was no internet back then.
Reply:I guess I told you guys, eh?  Now I gotta file this lab project on the "pending projects list"....City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by castweldmakoman I agree with your short list, or at least that is what you'll find in most publications. But when brazing cast iron- if I'm having bubbles in the puddle I will try a slight carburizing flame. Most of the time the bubbles (porosity) will disappear. If I machine a bead that was bubbling while welding it will be porous after cooling. I know this is against the "grain" of most publications, but it works for me. Try it you might like it.Peter
Reply:Originally Posted by makoman1860Matt, A reducing flame can have ANY feather length, neutral is NO feather. Distinctions have to be made as some materials are sensitive to even a 1x reducing flame, so when a neutral flame is required, it means neutral, not something around neutral.