What’s up guys and welcome back to another back to basics article. If you aren’t already SUBSCRIBED to the website go ahead and SUBSCRIBE and use the bell icon right next to it to be notified of upcoming articles. I’ll be explaining to you how to correctly braze a copper joint.
There are three 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 two is the actual brazing process which I’ll get to in just a minute, and step three finishing off the joint.
Alright so let me start off by explaining what brazing is, then pointing out the differences between brazing and 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 842 degrees Fahrenheit or 450 degrees Celsius by the American Welding Society, but is often rounded to 840 degrees Fahrenheit. If the filler metal melts below 140 degrees Fahrenheit the process being performed is soldering. Brazed joints are used for refrigeration, high pressure airlines and HVAC where maximum joint strength is a must and solder joints are used in low pressure applications such as potable water lines and some heating systems.
The tools and type of filler materials vary from a solder joint to a braze joint so let’s go through 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 such as this. 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’re doing.
In case of any doubts, don’t hesitate to ask your local plumbing supply shop for what type of rod you need to use for your application.
For this demonstration, I’ll be using a stay-silv 15 rod which contains 80% copper, 15% silver and 5% phosphorus. You’ll want to get a rod that contains phosphorus as their 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-inch 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 much higher temperature than normal solder. Oxy-acetylene burns much hotter at 3500 degrees Celsius or 6330 degrees Fahrenheit compared to propane which burns at around 1995 degrees Celsius or 3620 degrees Fahrenheit, and finally the torch.
When soldering, a torch like this is used seeing only one type of gas is needed. Plus, propane torches don’t give out near as much heat as the following, the oxy acetylene torch. 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 two tanks, one for oxygen and one for acetylene.
There’s also two 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 article . 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 want to consider is making sure your torch has flashback arrestors on both 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 article are some wire brushes, an inspection mirror and a fire extinguisher.
Alright, so with that out of the way, let’s get started! If your 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 some 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 deburr the inside of the pipe using either a round file or a dedicated pen reamer like this one. 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 material you’re dealing with. For this demonstration I’ll be using a number two tip from Harris.
Once both tanks have been filled, give them a quick purge to ensure no contaminants are going into the torch assembly. Install both regulators, then connect both of your hoses and finally the torch.
Now open up both tanks and adjust both regulators to around 5 psi.
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 quarter turn after the gauge reaches full pressure, this will 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 one trip to refill instead of two.
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 soot and smoke in the air, this is normal, just wait for both of them to clear up and slowly open up the oxygen side. There are three 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 three colors and lead’s 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 work piece which is unwanted. And lastly, a neutral flame. A neutral flame is what you’re looking for as it doesn’t carburized nor oxidize, it has a perfect mix of oxygen and acetylene and is typically a clear blue color like this. Before brazing make sure your pipes are well supported and make sure to have a fire extinguisher just as a precaution. The first part you wanna 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 in 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 want to 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 that 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 through. I always like to purge my hoses before saying I’m 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 is cooled down, get your wire brush and remove any scaling that occurred on the surface of the pipe.
You want to be able to inspect your work and make sure that 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.
Here’s an example of a purged line versus a non purged line. As you can see, there are enough contaminants that formed inside the pipe the clog a metering device or whatnot, the difference is obvious and should be taken into consideration when brazing on expensive equipment.
And that’s how to properly silver solder or braze a copper joint. If you’d like to see a great example on how to correctly solder a copper pipe I’ll put a link in the description box below that links to it In this article. You’ll learn all the necessary steps to correctly solder a copper joined with ease and with very basic tools.
I also have a ton of other informative plumbing articles to check out on my website so don’t miss out on them. If you found this article helpful, let me know in the comments below and as always if you like this type of article I invite you to subscribe to the website as I have more cool content on the way and until the next article, thanks for reading