Help with Brazing!
I'm working on a custom project and trying to braze a steel tube onto a steel plate perpendicular to each other. I'm using an Oxy-Mapp Worthington torch. I used 3/32 inch flux coated copper brazing rods. I added some water soluble soldering flux from the plumbing department. When I heated the metal, the flux turned black before the steel turned red. Should I even be using this flux or is there some other type I should be using? When I did add the flux coated brazing rod, the flux seems to melt off the rod quickly, but the copper melted very slowly. Also once I finally got the copper to melt, it beaded up quickly and I couldn't really control where to move it to. Once I finished the copper had adhered to the tube but not to the steel plate. As you can tell I don't really know what I'm doing. I watched some you tube videos but I must be doing something wrong. I'm thinking that I should probably be using smaller rods. Also, how far away from the inner blue flame should the metal be? How do I introduce the brazing rod, wait until the metal is red then touch it to the base metal? How far away from the inner blue flame should the brazing rod be? How should I clean up what I've done so far? I want to re-use this piece of steel tube. I was planning to grind some of it off then try to melt the rest of the copper off if I can then clean it up. What about cleaning up the black flux? It sounds like your base plate is not hot enough. Re-clean your parts until they are nice and shiny steel and try focusing your torch on the base plate. Your lighter weight tube will probably come up to temperature with just the flame spilling off the heavier base plate but you can control it by where you aim your flame. You want the flame concentrating on the heavy plate and if you need to bring it closer to or aim it a bit more at your lighter tube but definitely focus on the heavier piece. My problem is usually getting too much heat into the smaller part is the two pieces are very dissimilar in weight. Once both pieces are up to temp then bring in your filler rod. You don't want your rod in the heat before the steel is up to temp otherwise all you end up doing is melting off and oxidizing the flux. You said you are using flux coated copper rods........is this correct? If so copper rods are for brazing copper material only. You need to be using flux coated bronze rod which is for steel. There is a certain knack to working with brazing rod. When applying the flame and rod you have to manipulate both so the bronze filler does not overheat and flow like solder. You need just enough heat for the bronze rod to flow but be able to create a definite filet that joins the two pieces together. To do this you need to heat up as much of the object as you can but not to the point that the bronze rod will melt when you touch it to any place on the metal. You need to preheat and then apply heat and rod so that the rod only melts just behind the tip of the flame. This allows you to get a high filet that can bond to both pieces. Here is a simple explanation. What could be a better bonding method is to use silver solder. As strong or stronger than brazing it has some advantages. The metal has to be very clean but when you apply the silver solder it flows into the joint like solder. This reduces flexing of the base material as it could when brazing and keeps whatever you are working with from becoming distorted. Adding extra flux might help but there should be enough on the rod. The only thing I will do is when restarting a fresh braze will cut off the end of the rod where the flux has melted off so it is like you are starting with a new rod. Another thing is you need to adjust the torch for a carbonizing flame. This is where you light the mapp to get an initial flame and then add oxygen so that the smoky flame decreases until the point that two distinct flames merge into one. This is a neutral flame. If from this point you add a bit more oxygen the flame will become more intense which is an oxidizing flame and too hot for brazing. If you back off from an oxidizing flame by decreasing the oxygen to neutral again then cut back the oxygen ever so slightly so that you have the beginnings of two distinct flames this is an oxidizing flame. An oxidizing flame gives you lower temps at the tip of the flame and allows you to better control of the brazing rod. You are going to have to grind off all traces of the copper and flux to make it look like shiny new metal. @GregH, yes I'm using Copper brazing rods. In the instructions it said they can be used on different materials, including steel Shop Lincoln Electric 1 lb 3/32-in Flux Coated Copper Brazing Rods at Lowes.com Should I get thinner rods? Do I need extra flux? The extra flux I used turned black so maybe I should not add any additional flux. Do I pull back the flame when introducing the rod or keep the tip of the flame on the rod? Should I have the tip of the flame on the metal, or what part should I use? @PilotDane, Thanks, good tips. Uh, no. Copper rods are not for steel. The link you gave us specifically says that rod is for copper. Check to make sure that if the instructions say it is for steel that no one switched instructions. You need flux coated bronze rod. Copper WILL weld steel to steel. Coming from personal experience. Brazing rods melt a little easier because of their lead and zinc content. The copper rods usually take a massive amount of heat to melt being as copper releases its heat very quickly! Copper is a good metal to use for artsy stuff, not for work load items. Brazing rods are used on items that usually have some sort of stress on them, like engine blocks and supporting pieces. Whatever, Good luck to ya partner! Curious to know exactly what copper alloy you have used to join steel. Are you referring to the small amounts of copper found in some alloys like silver solder and bronze brazing rods? The only rod I am aware of that contains copper in any appreciable quantity is Sil-F oss and other silver phosphorus rods and is only for steel. Mild steel brazing rod often comes copper coated to prevent rusting but the copper floats to the top of the braze as a waste product. Brazing with Copper Wire - YouTube Argument ended. Just clean a old coat hanger and use it for filler rod.
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