Similar to resistance welding, resistance brazing employs heat to bond materials with high electrical conductivity. As indicated by its name, the process uses the principle of resistance to generate the heat necessary for its operations; as electrical current flows through a circuit that includes a workpiece, the circuit’s resistance produces heat.
Like resistance welding and other welding methods, resistance brazing requires specialized equipment—typically a transformer, electrodes, and a pressure source. Its key distinction is that it involves the use of additional brazing material to join parts together.
A resistance brazing operation typically includes the following stages:
1. Preparing all components, including electrodes, to remove surface contaminants.
2. Fixturing all components in the assembly.
3. Establishing the circuit that includes the workpiece.
4. Placing filler material (usually in pre-formed or foil) between the surfaces of the joint.
5. Running current through the circuit to generate the heat necessary to melt the filler material and develop a metallurgical bond between substrates.
6. Turning the electrical current off and maintaining pressure to allow the braze material to solidify and form a solid connection between the two components.
7. Removing the finished joint from the fixture and taking off any remaining flux.
8. Inspecting the finished joint.
Compared to other welding methods, resistance brazing offers several advantages. For example, in contrast to traditional spot welding, resistance brazing provides the following:
● Higher temperatures to bond conductive metals, such as copper or brass, that could not otherwise be joined.
● Easier operations as resistance brazing need only to bring the filler material to its melting point, not the workpiece itself.
● More localized heating, ensuring other parts of the workpiece remain protected and retain their strength.
● Lower investment cost as the necessary equipment is fairly inexpensive.
● Greater portability is useful for processing large equipment that cannot easily be transported.
While resistance brazing offers many advantages, it may not be the right choice for every application. Due to the use of localized heating, workpieces are susceptible to distortion. Brazing materials also need to have low melting points, as the workpiece is made of highly conductive materials. Additionally, the process is not ideal for large joint areas; it is more practical for use on smaller joints.
While not ideal in every scenario, resistance brazing does benefit many manufacturing applications due to its:
● Ability to form permanent bonds between base materials.
● Economical cost for both simple and complex assemblies.
● Lower temperatures and more even heat distribution when compared to welding.
● Effectiveness in joining thin and thick metals.
● Capacity to maintain tight dimensional tolerances.