How to CORRECTLY Braze (SILVER SOLDER) a Copper Pipe

4,088

36

19

Introduction: How to CORRECTLY Braze (SILVER SOLDER) a Copper Pipe

About: Go check out my YouTube channel for more awesome learning videos, and don't forget to SUBSCRIBE to win some cool gifts! WWW.YOUTUBE.COM/GOT2LEARN

So, today I’ll be explaining to you how to correctly braze a copper joint. There are 3 easy steps to getting this accomplished.

The first step is to prepare the joint. Skipping this step may result in an improperly brazed joint.

Step 2 is the actual brazing process which I’ll get to in just a minute.

And step 3, finishing off the joint.

Step 1: BRAZING VS SOLDERING

Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a material into the joint, the filler material having a lower melting point than the adjoining metal.

The difference between brazing and soldering is the temperature necessary to melt that filler metal. That temperature is defined to be 842ºF/450ºC by the American Welding Society (AWS) but is often rounded to 840ºF. If the filler metal melts below 840ºF the process being performed is soldering.

Brazed joints are used for refrigeration, high-pressure air lines and HVAC where maximum joint strength is a must, and soldered joints are used in low-pressure applications such as potable water lines and some heating systems.

Step 2: TOOLS/MATERIALS FOR THE PROJECT

The tools and type of filler materials vary from a soldered joint to a brazed joint, so let’s go thru both of them together.

When soldering potable water lines, you’ll be using this type of solder which is called 95/5. This type of solder can’t be used when brazing so, you’re gonna be needing a filler material. There are many types of filler materials on the market and you’ll need to choose the right one depending on the type of job you are doing. In case of any doubts, Harris products does supply a very clear chart on what type of brazing rod to use for various types of materials being joined. For this demonstration, I’ll be using a Stay-silv 15 which contains 80% copper, 15% silver and 5% phosphorus. You’ll wanna get a rod that contains phosphorus as they’re self-fluxing, removing the need to apply any flux on the pipe.

Seeing silver solder melts at a much higher temperature, you’ll be needing more heat than your typical soldered joint.

Brazing smaller pipes is possible with a small propane torch, but larger pipes such as 1” and up require more heat, therefore, it’s recommended to use an oxy/acetylene system with an appropriate torch seeing silver solder melts at a higher temperature than normal solder. Oxyacetylene burns much hotter, at 3500*C or 6330*F compared to propane which burns at around 1995*C or 3620*F.

And finally, the torch. When soldering, a torch like this is used seeing only one gas is needed. Plus, propane torches don’t give out near as much heat as an oxy/acetylene torch does.

I’m using this oxy/acetylene port-a-torch kit from Harris, which is a Lincoln electric company and is great for light-duty brazing tasks such as this one. It comes in a carrying tote and there are 2 tanks, 1 for oxygen and 1 for acetylene, there’s also 2 regulators for each gas and the actual torch. You’ll also notice the torch tips that come with the kit, but we’ll talk about these later in the video. You could use a simple air/acetylene setup like this, but it’s considerably longer and doesn’t give you a clean joint like an oxy/acetylene kit does. However, they are more economical and lighter to carry around in tight spaces, so use what’s best for you.

Something else you might wanna consider is making sure your torch has flashback arrestors on the oxygen and acetylene side. Most new torches come with them built in. In the past, these were separate and needed to be installed on the hose itself. So just make sure your kit is equipped with them as they’ll stop a flame from going into your tank, which you don’t really want.

Some other things I’ll be mentioning in the video are some wire brushes, an inspection mirror, and a fire extinguisher.

Alright, so with that out of the way let’s get started

Step 3: BRAZING

If you are brazing on a refrigeration or cooling system with costly components, it’s highly recommended to purge your lines with an “inert gas” such as argon or nitrogen. During the brazing process, a lot of oxidation will occur inside the pipe, creating scale that could potentially clog these costly components and even, void a warranty. In this demonstration, I’ll be skipping this step.

So the first thing that needs to be done is to clean our pipe and fitting. For the pipe, I either use sandpaper like this or just an abrasive pad. This step is very important, as “proper wetting” is somewhat influenced by the pipe and fitting’s cleanliness. Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. In other words, your filler material won’t fuse properly if they aren’t perfectly clean. Also, de-burr the inside of the pipe using either a round file or a dedicated pen reamer.

Now’s a good time to choose what tip you’ll be using for your application. Each manufacturer comes with a chart that specifies what tip you need for whatever thickness of the material you are dealing with. For this demonstration, I’ll be using a #2 tip from Harris.

If your kit comes disassembled like this one, go on and install both tank valves on their respective tanks without any thread sealants such as Teflon tape or pipe dope. Once both tanks have been filled, give them a quick purge to ensure no contaminants are going into the torch assembly. Then, connect both of your hoses and finally the torch.

Now open up both tanks and adjust both regulators to around 5Psi. Once full pressure is reached on the oxygen side, you could fully open the valve. On the acetylene side, however, it’s recommended to open the valve only a ¼” turn after the gauge reaches full pressure. This’ll allow for easy closure if an accident occurs. More pressure than this will result in an unstable flame so I recommend sticking with these numbers. Also, using the same pressure on both tanks means they’ll deplete equally which means 1 trip to refill instead of 2.

Go ahead and first open the acetylene knob about halfway and light the end of the torch with a striker like this. You’ll see a mix of soothe and smoke in the air, this is normal, just wait for both of them to clear up and slowly open up the oxygen side.

Step 4: TYPES OF FLAMES

There are 3 types of flames. One you don’t want is a carburizing flame. Here’s what a “carburizing flame” looks like, it’s easily distinguished by its 3 colors, and leads to excessive carbonization on the pipe which isn’t necessary and could compromise the joint. Secondly, is an oxidizing flame which you don’t want either. This type of flame, as the name states, will oxidize your workpiece which is unwanted. And lastly, a neutral flame. A neutral flame is what you are looking for as it doesn’t carburize nor oxidize, it has a perfect mix of oxygen and acetylene and is typically a clear blue color like this.

Step 5: MORE BRAZING

The first part you wanna to heat is the pipe, the reason being is that between the fitting and the pipe is a small gap of air. Seeing air doesn’t transfer heat very well, it has to be heated independently, in the beginning, to make sure it reaches brazing temperatures. Once the pipe has been heated, start heating the fitting’s hub, always staying in motion. Every once and a while, use your filler material to test if it’s hot enough, and once it is you’ll see it start to melt. At this point, you wanna make sure you don’t heat the actual filler material, you want the heat from “the joint” to melt it so, to make sure you do it the right way, don’t apply any concentrated heat on the actual brazing rod itself.

You may notice your pipe becoming red hot but don’t use more heat than that as to not overheat it. As I mentioned earlier, proper wetting is crucial when brazing and overheating the joint will inhibit proper capillary action. Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. A good example of capillary action is when a paintbrush or paper towel is dipped in a liquid. The liquid is absorbed without the aid of external forces. When you feel that the joint is completely filled, apply a small filet or cap where both the pipe and fitting meet. A proper filet or cap should be concave just like this.

When you’re finished brazing, slowly close the oxygen knob on the torch, followed by the acetylene knob and then close both tank valves to make sure no gases are passing thru. I always like to purge my hoses before saying I am completely done.

With your joint properly brazed, wait for it to cool down naturally. Applying water to a heated pipe as such could cause a fracture in the joint, resulting in a leaky joint.

Once the joint cooled down, get your wire brush and remove any scaling that occurred on the surface of the pipe. You wanna be able to inspect your work and make sure there aren’t any voids. If you’re in a tight spot, a mirror could help you analyze your joint to see if any adjustments may be needed.

Water Contest

This is an entry in the
Water Contest

Share

    Recommendations

    • Tiny Home Contest

      Tiny Home Contest
    • Water Contest

      Water Contest
    • Fix It! Contest

      Fix It! Contest

    19 Discussions

    Thanks for the lesson. Any thoughts on MAPP gas to do brazing? I have that because it claims to run hotter than propane but I am more reluctant to keep a canister of pure 02 and acetylene in the hot garage.

    2 replies

    Yes, you can probably get a brazed joint completed with MAPP gas on smaller pipes such as 3/8" and maybe even 1/2" if you are lucky, but I recommend doing it done with an oxy/acetylene setup as it's a lot quicker. If you try it out, please let us know if you succeeded or not ;) Cheers!

    Soldering and brazing are not the same thing. So you started off incorrectly. Too bad you capitalized correctly, because you got it wrong.

    Soldering requires less heat in that the solder is melted and flows into the joint.

    Brazing requires much more heat in that the material being joined is heated to its melting point and allowed to coalesce to help form the joint. And a rod is also melted to add to the joint.

    4 replies

    "This from Wikipedia"

    A source worth checking, of course. However no certainty that the information there is perfect. Best find an authoritative source or two to cite as primary sources when you can. In this case, the wiki worked.

    Then again, he could use PEX ;)

    Incorrect. The base material is not heated to its melting point and there is no coalescing of material in the parts to be joined. You can braze cast iron to steel, where cast iron has a melting temp of ~2150F and bronze (the filler material) has a melting point of ~1750F.

    I feel like you didn't actually read this article. It's excellently written, and is clear about the differences between soldering and brazing.

    Rubbish! The author got it absolutely right. This from Wikipedia:

    Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal.

    Brazing differs from welding in that it does not involve melting the work pieces and from soldering in using higher temperatures for a similar process

    You were confusing brazing and welding. If you are going to criticise, at least get your facts right!

    "Something else you might wanna consider is"

    English perhaps?

    It is also polite to link to or reference your sources. (Saves comments like the fellow who thought "... you started off incorrectly.")

    I like the following from https://www.copper.org/applications/plumbing/techc...

    "The most common method of joining copper tube is with the use of a socket-type, copper or copper alloy fitting into which the tube sections are inserted and fastened by means of a filler metal, using either a soldering or brazing process. This type of joint is known as a capillary or lap joint because the socket of the fitting overlaps the tube end and a space is formed between the tube and the fitting. This space is called the capillary space. The surfaces of fitting and tube that overlap to form the joint are known as the faying surfaces. Tube and fitting are then solidly joined using a filler metal that is melted into the capillary space and adheres to these surfaces.

    "The filler metal is a metal alloy that has a melting temperature below that of either the tube or fitting. The melting point of copper (Cu) alloy UNS C12200 is 1,981°F/1082°C. As such, the filler metals for soldering and brazing copper and copper alloy tube and fittings must have melting temperatures below this temperature.

    "The basic difference between soldering and brazing is the temperature necessary to melt the filler metal. That temperature is defined to be 842ºF/450ºC by the American Welding Society (AWS) but is often rounded to 840ºF. If the filler metal melts below 840ºF the process being performed is soldering. Above that temperature, the process is brazing.

    "Brazed joints are generally used to achieve higher joint strength or fatigue resistance. To accomplish this, filler metals stronger than those composed primarily of tin must be used. However, this increased strength generally comes from filler metals made of materials that melt at higher temperatures. The brazing temperatures for most of the brazing alloys used to joint copper piping systems (BCuP and BAg alloys see below) are roughly between 1,150°F/621°C and 1,550°F/843°C.

    "The most commonly used brazing filler metal types, used to join copper tube and fittings fall into two distinct categories:


    • BCuP Alloy (pronounced b-cup) - where the B stands for Brazing, Cu is the chemical symbol for Copper, and P is the chemical symbol for Phosphorous. Therefore, a BCuP brazing alloy is primarily a copper-phosphorous brazing alloy that may contain from 0%-30% Silver (Ag).
    • BAg Alloy (pronounced bag) - where the B stands for Brazing and Ag is the chemical symbol for Silver. While there are other elements found in BAg alloys besides silver, the majority of BAg alloys may contain silver content of anywhere between 24% and 93%.
    2 replies

    That was a nice tutorial, but where you say

    "

    The liquid is absorbed without the aid of external forces. When you feel
    that the joint is completely filled, apply a small filet or cap where
    both the pipe and fitting meet. A proper filet or cap should be concave
    just like this."

    there is no picture. I must say though when I was taught to solder, we always want the heated object to melt the solder, be it copper pipe or electronic circuits. Solder willl wick in nicely.

    Thanks for explaining it I always wondered how that worked. And telling the proper order of "powering up" and "shutting down" to a newb is great.

    1 reply

    Ok, i'll add a picture for that part, I guess I forgot about it lol, thanks for the great comment! EDIT** I just checked and yes there is a picture, it's this one right here, cheers!

    FYLKQ4UJK2UHCMO.LARGE.jpg

    Why have you not used any Flux (usually a paste of Borax and water) this keeps the joint free of oxides at elevated temperatures? OK, I know you can use special brazing rods that do not require flux????? but cost much more..........after cleaning the join apply with a brush - heat gently to dry off the water then heat fully to red, the fux shoud be glassy clear and when you touch the rod on the join it will run really nicely all round and into the join = success..............

    a valuable lesson. Perhaps less "wanna" and "gonna" would be nice.

    1 reply
    0
    None
    ctmcc

    14 days ago

    Silver Solder and knowing how to use it properly is a very valuable lesson. Knowing how to Braze has saved me many times. I keep a small quantity of silver solder in my welding kit bag and tanks of Acetylene and Oxygen in my garage at all times. The gas bottles are not dangerous if stored properly. Great lesson, very well done!

    1 reply

    Thanks for the great comment!

    I will only say, nicely, that silver solder makes fine butt joints in copper, and that you can use multiple torches for larger pipes.