Induction brazing has emerged as a leading method for joining copper in various HVAC, automotive, and electrical industries. It offers numerous benefits, including precision, speed, and repeatability, making it a preferred choice for many applications. However, it requires specialized equipment and knowledge to achieve optimal results.
In this article, we will guide you through the induction brazing process of copper, covering everything from surface preparation to filler material selection.
Read on to discover how to leverage induction brazing to create strong and reliable copper joints for your specific needs.
Induction Brazing Copper: The Complete Process
A brief knowledge of induction heating and brazing is required to understand copper brazing.
Induction heating is melting metal workpieces by passing high-frequency AC through them. While brazing is a simple metal joining process in which two metals are joined by infusing a filler metal between them.
Brazing has many types based on the heat source employed. However, when an induction heater is used as a heat source for brazing, that is known as induction brazing.
The process of copper brazing involves multiple steps, which are outlined below:
Step 1: Cleaning the Copper Piping
To prepare the pipes for brazing, they are thoroughly cleaned inside out with a wire or rubbed with sandpaper to eliminate all contaminants. This step is necessary for a clean and robust induction brazed joint.
Step 2: Preparation of an Overlap/Socket Joint
Next, an overlap joint is formed to braze the copper pipes. This is a critical step since the strength of the joint will ultimately depend upon the overlap depth of pipes. As per the American Welding Society (AWS), the depth should be at least three times the thickness of copper pipes being brazed. Normally, industries go with much higher values to be on the safe side.
Step 3: Clamping the Pipe Setup
Clamping of the setup is also necessary to keep the joint in place before brazing. The pipes are temporarily clamped inside an induction coil or outside of it.
Since the induction coil is the heat source in this brazing technique, the whole need setup needs to be surrounded by it.
If a portable induction heater is used, the induction coil is usually placed over the clamped pipes setup. However, in some cases, the whole setup is placed inside the heavy-duty induction machine.
Step 4: Application of Filler Metal
The induction heater is turned on, and a filler metal, usually a rod, is applied to the joint. Based on the power rating, the heater remains turned on for 5 to 10 seconds. The higher the power rating, the less time it takes to braze the copper pipes.
Step 5: Cooling
After the brazing process has been performed, the copper joint is allowed to cool for an hour before it is ready for use.
Filler Metals and Flux used in Induction Brazing of Copper
Since we discussed fillers in the previous section, it is important to mention the common ones used. For induction brazing copper, two series of filler metals are employed:
- BCuP alloy series
- BAg alloy series
BCuP series alloys are rich in phosphorus, which acts as a flux during induction brazing. From this series, BCuP-2 is quite common for plumbing and HVAC applications. While for general piping applications, BCuP-3,4 or 5 are used as they are cheaper. The BAg alloy fillers are used when joining copper with dissimilar metals.
One of the pertinent points to note here is that the strength of an induction brazed doesn’t depend on the filler metals used. Instead, it is a function of clearance and overlapping depth between the two joined pipes.