Do you want to learn to braze copper? If so, then this article is for you! In the following paragraphs, we’ll go over the process of brazing copper by using a torch. We will also discuss how it’s done with flux and solder paste. You can use either method of brazing if you want – they both work just fine. Let’s get started!
What is brazing?
Brazing is a heat-sensitive bonding process where a filler metal can be used to join two metals together.
It’s often done as welding, but it only uses the flame’s heat without any liquid, gas, or electricity. For this to work successfully, brazing has to occur in a vacuum chamber (which we’ll go over how you can set up) because residual air molecules will interfere with the process, weakening how strong a bond occurs between metals joining by brazing. Filler metal is molten and brushed onto one surface and then melted on another until alloy plating forms on both surfaces and causes them to become similar materials bonded together.
Why would you want to braze copper?
Brazing copper is how you can connect copper pipes, typically for plumbing. You would need to be a licensed plumber to use this method, though, and the opportunity to braze a pipe usually doesn’t come up.
While it’s not a frequently used technique, brazing copper is how you can connect two pieces of copper pipe. If this opportunity came up for you and you’re licensed to do plumbing work, then feel free to use your newfound knowledge by braze welding the pipes together! I should note that if residual air molecules are present, the brazing process will be less successful.
Do you need flux to braze copper?
To braze copper, you need flux just so that solder can run freely and is heated by the torch. The rod is then pushed into place without being forced, which would mix up the heat bath and create an unreliable connection between two pieces of copper.
The simplest method for brazing copper is using a flux brush on one surface and then molten metal being brushed onto it – this will also involve water-soluble paste. The two pieces of metal should have a sanded surface for this process to work efficiently because otherwise, it won’t form an advantageous bond between them. This technique is often how plumbing pipe joints are done because no one wants toxic fumes from soldering around inside their home.
How to braze copper
Brazing is done by heating the copper, then running a layer of constantan (a type of metal with high thermal conductivity and low electrical resistivity) on top. If you line up the two pieces correctly, they will fuse when heated to 250°C. The flux ensures that any small air bubbles don’t get in there and ruin it all – these will bubble to the surface as it’s heating and can be pierced with a brazing needle before heating starts.
Once they’re heated, apply some braze solder paste – this will melt when heated again to complete the joint! If constantan doesn’t provide enough thermal conductivity, or you want to make sure both pieces are at roughly the same temperature before applying heat for the first time, you can also use a flux-covered brazing rod.
What exactly happens when the filler metal melts?
When the filler metal melts, it will usually form a bright orange glob. This is how you can know that you’ve reached the correct temperature to proceed with the brazing process. You should apply the flux and water-soluble paste, then you should heat the rod and copper pipe for about five minutes before adding solder paste onto the rod.
If you’re wondering how you could do this in construction, it’s typically how plumbing pipes are connected. With plumbing pipes, there are two methods commonly used: brazing copper and soldering copper.
The flux will help the solder flow freely and should be applied to both surfaces for a successful brazing process. The rod is then pushed into place without being forced, which would mix up the heat bath and create an unreliable connection between two pieces of copper.
How it’s done with flux and solder paste
If constantan doesn’t provide enough thermal conductivity, you can use a flux-covered brazing rod to join copper together. Applying paste ensures that the joints are strong and durable. If you choose to use flux and solder paste, the process is as follows:
- Apply a layer of brazing solder paste on copper pieces.
- Place both sides together.
- Heat with an oxyacetylene torch until joints are fused – this will take about two minutes per inch or so. If it’s not hot enough for solder, it will just absorb the solder into the flux, and you’ll have to start again.
- Apply to braze heat with an oxyacetylene torch.
- When heated enough, apply braze paste until the joint is complete!
Can I braze copper with a propane torch?
Yep. The torch heats the edges of the copper and cools them in water. All excess water is blown away with a light stream of air from the torch before welding starts.
“Welding” means joining two pieces of metal by melting and blending their surfaces to form a strong connection that will not break easily up to 800 degrees F (426 degrees C). When you start brazing, first heat one end for 1-2 minutes. Brazing has several advantages over other methods: it’s relatively easy and inexpensive to get started with. It doesn’t require large amounts of electricity or gas as some other brazing methods do. Techniques are easily acquired through practice without formal training. Braze joints have low strength until cooled but are stronger than solder joints.
The torch heats the edges of the copper and cools them in water. All excess water is blown away with a light stream of air from the torch before welding starts.”
Brazing has several advantages over other methods: it’s relatively easy and inexpensive to get started with. It doesn’t require large amounts of electricity or gas as some other brazing methods do. Techniques are easily acquired through practice without formal training. Braze joints have low strength until cooled but are stronger than solder joints.
What about brazing copper tube or copper pipe?
Copper tubing is a great metal to use for water pipes because it’s resistant to corrosion and rust. When you’re soldering, there are some things you can pay attention to that will help the brazing process go more smoothly.
- Ensure that the pipe is clean and free of any debris before applying flux. If there’s any dirt or grease on the copper pipe, if risks, how much solder will be absorbed into the joint. Clean the pipe with soap and water or with a wire brush before starting.
- Put flux on both sides of the copper tube (the flux should always contact metal surfaces) and heat one end for 2-3 minutes. Once heated, apply solder paste to the heated surface and apply heat again. Allow it to cool for a few minutes before applying more solder paste on either side of the joint, reheating until both pieces are hot enough that when you touch them with your finger, they don’t feel cold or tingly; if not, then repeat heating.
- Allow brazing material to cool before running water through it.
- A pipe that has already been brazed and is in use should be flushed with a non-toxic cleaning solution every year or two to remove any mineral deposits which may cause leaks, corrosion, and build-up of bacteria.
No matter how you do it, though, the process for joining copper pipe using solder or braze is the same:
- Apply flux to both pieces of copper.
- Heat one side until it feels hot for about two minutes and applies solder paste, reheating with the oxyacetylene torch if necessary.
- Allow brazing material to cool before running water through it.
How to clean up after brazing
After the brazing process is completed, you will need to clean the dirty flux off of your project. To do this, wash it with some soapy water and then rinse it with clear water a second time. Be sure to wipe away all of the excess water before beginning your next step.
How to avoid any potential problems when brazing
It’s worth looking for any signs of leaks – tiny beads of molten metal and smoke. If you see them, quickly cover the hole with a wet rag or baking soda to prevent sparks from igniting the gas; then add some more flux (if your rope brazing process includes it) and continue brazing.
Can copper and stainless steel be welded together?
Yes, copper and stainless steel can be welded together. This type of welding is known as brazing, and it’s how the copper plumber joins the pipes in the plumbing system. Brazing uses a filler metal that melts at a much lower temperature (about 700 degrees F/356 degrees C) than ordinary welding does (between 2,000-2,700 degrees F).
The heat needs to be high enough to melt metal on both parts where they connect. A brazer then squeezes how flux onto one part or the other – whichever surface doesn’t have solder on it already – before heating it with an oxyacetylene torch until molten pools fill up all of the little gaps between the two surfaces.
What’s the difference between flux coated and uncoated?
Flux coated copper brazing rod is just a trade name for galvanized rods that have been dipped in flux. If you’re thinking about how to braze copper and how long before I should use the rod, this coating will only last so long before it needs to be reapplied. Personally, I find flux uncoated rods easier to clean up – no holds barred – whereas with coated, sometimes all of the pulverized solder slag gets stuck on the surface, and it takes more elbow grease to get it off.