Join us as our technical team outlines the main elements used in brazing filler metals, along with the most important features of each element. The more you understand about these elements, the better equipped you are to choose and use the correct products for your brazing operation.
Braze Joint Repair: Aluminum Heat Exchangers
Having clean base materials is one of the Six Fundamentals of Brazing that ensure quality braze joints:
1. Good fit and proper clearance
2. Clean base materials
3. Proper flux/atmosphere
4. Proper fixturing
5. Proper heating
6. Final cleaning
You want brazing solutions designed for your needs – whether you are manufacturing air conditioning systems for automobiles or highly sensitive jet turbine blades or even components for satellites. Find out which brazing alloys and consumables meet your specific needs.
The most common brazing processes include torch, induction, furnace and resistance brazing. Of these methods, resistance brazing is the least common heating method. Why? Compared to the others, it is a fast and relatively inexpensive process, but limitations in assembly geometry have restricted its practicality. However, today’s technology has expanded resistance-brazing applications to more complex assembly styles.
Resistance brazing is very similar to spot welding. Both processes heat the base materials by sending direct current through the joint interface. While welding melts the base materials together, resistance brazing only melts the brazing filler metal.
Carbide inserts can provide superior wear resistance and prolonged life in cutting and wear processes. These mechanical properties make carbides useful for mining tools, cutting tools, wear parts and other applications. Let's look at the joining process used to attach carbides to their holders. For this discussion, we will focus on tungsten carbides containing a cobalt binder.
The most common brazing processes include torch, induction, resistance and furnace brazing. In furnace brazing, filler metal in the form of pre-forms or paste is placed onto an assembly to be joined. This type of brazing includes either a protective atmosphere or the evacuation of the surrounding atmosphere-called vacuum brazing.
Because of tolerances, aesthetics or joint design, you sometimes need the flow of braze alloy to be restricted-to stop its flow or keep it off a surface. Capillary dams are often designed into these parts to limit braze alloy flow. A capillary dam is when the clearance is increased to a point where capillary action no longer exists. Ideal clearances for the best capillary strengths are .000"-.002" in furnace, and .002"-.005" in open air. Anything over .012" is preferred as a capillary dam. When the assembly cannot be designed to naturally prevent braze alloy flow, a brazing aid called Stop-Off can help you prevent or guide the flow of braze allow on your assembly.
Depending on your brazing process, you may need to perform post-braze joint cleaning to remove residual flux. This step can be crucial since most fluxes are corrosive. Post-braze cleaning is one of the Six Fundamentals of Brazing*.