Brazing is the joining of like or unlike metals wherein the base metal doesn’t melt along with the filler metal. Instead, only the filler material melts.
This process involves filler metal, also known as brazing metal. Although the brazing metal has a melting point of 840°F, it’s still below the adjoining piece’s melting threshold.
Brazing is particularly useful in fusing similar or dissimilar pieces of considerable strength.
You can do brazing when you want to join different metals with varying melting points. It’s a simple process that doesn’t usually require post-processing heat treatment.
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What is Brazing?
Brazing is another metal-joining process similar to welding and soldering. These three may all seem alike, but these processes differ in specific ways.
Welding differs from brazing because it doesn’t melt the workpieces. It uses a higher temperature than soldering and brazing to apply the filler metal.
While brazing can easily fuse dissimilar metals, it can be difficult to weld the wrong metals together as it may create a weak link.
Aside from that, the brazing temperature is lower when compared to the welding temperature. Although welding creates stronger welded joints.
Now, what about soldering? Soldering also unites metals together but with the help of a solder. This is a metal alloy made of tin and lead.
The alloy used in soldering melts with a hot iron at 600°F, which cools to create a solid electrical bond. This temperature is lower than what brazing requires. That’s because the alloy has a lower critical temperature than the adjoining piece.
Soldering is particularly useful in fusing electrical metal parts. That’s to form an electrical bond which is widely used in the electronics industry.
How To Braze Metal?
If you’re still learning how to braze metal, it’ll help to start with mild steel. It’s an easy piece to work with.
The following are steps on how to braze mild steel using an oxygen-acetylene torch:
- Prepare the oxygen-acetylene torch. Open the acetylene knob and light the torch.
- If you notice a black soot, add more acetylene to get rid of it.
- Gradually add more acetylene until you get the “acetylene feather” in the flame.
- Turn the oxygen knob to begin introducing oxygen to the acetylene flame.
- The goal is to get a neutral flame by adding more oxygen.
- You’d know it’s a neutral flame once you see a small blue cone nearest the torch tip.
- Prepare your mild steel pieces.
- If the two pieces are of the same diameter, say a quarter of an inch, heat them evenly.
- Target the torch flame over both pieces uniformly so they both get evenly hot.
- Place the brazing metal between the torch flame and the metal to be brazed.
- Cool down the brazed joint and clean it with a wire brush.
- You have to heat the metal pieces to red hot, or they won’t hold together.
- If you overdo the heating, wherein the steel begins to melt, you’ll have an uneven brazed joint.
- It’s essential to adjust the flame depending on the metals you want to fuse.
- Rotating the torch is helpful when brazing lighter materials with heavier materials.
Once you master the skill, you can start working on other metals. You can braze copper to steel or lighter material to heavier material.
Methods of Brazing
There are various types of brazing available, with each type having a specific application.
1. Torch or Manual Brazing
The most common type is torch brazing. Manual torch brazing uses a hand-held torch similar to the one used in gas welding.
Note that the fuels used in torch brazing vary based on the type of workpiece and filler. Acetylene is for a workpiece that has extremely high-temperature tolerance.
This brazing method is tedious due to the manual process. However, it’s highly adaptable when working with challenging pieces.
Your skill in performing this is crucial as you need to be engaged to control the flame, manipulate the hand-held torch, and judge the flame’s temperature. All these measures ensure a proper joint.
Torch brazing is helpful for small productions.
Steps In Torch Brazing
- In torch brazing, a flux is applied first to the surface.
- Direct the low-oxygen flame against the workpiece and towards the joint using the torch.
- Once the two metal areas reach a suitable temperature, add the filler wire.
- Due to the high temperature, the filler wire melts and creates a joint.
2. Furnace Brazing
In this type of brazing, you use a furnace to supply heat. While torch brazing is excellent for small productions, this method is great for mass-producing parts. It suits medium to high production rates of components.
Steps In Furnace Brazing
- Place parts and brazing metal into the furnace.
- Heat the parts and brazing metal to the brazing temperature, which is 840°F.
- The high temperature melts the brazing metal fusing the joints.
- Cool and remove the workpiece.
3. Induction Brazing
One thing that sets induction brazing apart from other types is how it joins two or more pieces using a filler metal through induction heating.
You can join various metals in induction brazing, even ferrous to non-ferrous metals. These materials include nickel, steel, titanium, cobalt, copper. Other examples are non-metals like ceramics, glass, and graphite.
Induction brazing is an excellent way to safely fuse dissimilar metals and alloys. That’s because it uses an electromagnetic field instead of an actual flame. The heat is confined where it needs to be and joins the metals without melting them.
4. Dip Brazing
This method involves aluminum as the filler material and salt or metal bath as its heat source. What happens is that you have to immerse the workpiece and the brazing metal in the salt bath that contains a mixture of fluxing ingredients.
The dip serves as a heat medium and a flux for the joint. With the help of the flux, the filler adheres to the metal surface. This results in a clean and tight seal between the adjoined parts.
The equipment you need for brazing would depend on what workpiece you have and what method you’re trying to employ.
If you’re going to do torch or manual brazing, you should use an oxygen-acetylene torch. While if you’re doing furnace or induction brazing, you should have a furnace or an induction heating system.
Advantages and Disadvantages of Brazing
While brazing may have its pros, such as being used in mass production processes, it also has its cons. Here are some points to consider when understanding the brazing method.
The following are some advantages of brazing:
- You can braze various metals and non-metals.
- You can braze similar and dissimilar metals quickly, which is difficult in welding.
- Brazing produces a neat permanent joint.
- Brazed joints are more substantial than soldered ones.
- Brazing involves less heat and power compared to welding.
Brazing also has disadvantages, so it’s better to implement other metal-joining methods sometimes.
- Brazing doesn’t produce a joint as strong as a welded one.
- Filler metals used in the process can be costly.
- The resulting joint color may appear different from the base metal.
- Brazing is an inefficient method when trying to join large parts of metal.
You can also do tack welding if you want to join large parts temporarily. It fuses thin metal pieces before the final welding.
By now, it’ll be easy to answer the question: What is brazing? It’s a metal-fusing process involving brazing or filler metal to create a joint.
There are many uses for brazing. It’s applicable for different industrial purposes to produce other materials. It’s also a neater and safer way to join similar and dissimilar materials.