Industrial equipment and welding societies throughout the world recognize flux as a mixture of chemical compounds that aid in preventing oxide formation and unwanted substances on metal surfaces or molten metal. Flux prevents these from occurring as well as having to remove them. Most importantly, flux has a critical role to play when it comes to silver solder. Industrial equipment and welding societies throughout the world recognize flux as a mixture of chemical compounds that aid in preventing oxide formation and unwanted substances on metal surfaces or molten metal. Flux prevents these from occurring as well as having to remove them. Most importantly, flux has a critical role to play when it comes to silver solder.
Flux is usually applied to joints before they are brazed. When the joint is heated for malleability, the chemical compounds in flux are activated. When the components of flux are activated, there are three main functions.
1. Dissolve and absorb any leftover oxides on the filler or metal surface
2. Prevent metal surfaces from oxidizing throughout the heating process by eliminating oxygen from the surface
3. Increase the flow of the molten metal as it creates a smooth and clean surface
Flux Applications
One of the main applications that flux is used for is silver brazing. These types of fluxes are made from fluorides and potassium salts dissolved in water. As there are many types and combinations of fluxes, the metal for the filler and surface needs to be identified before choosing the proper flux.
Flux For Base Metals
Depending on the type of metal in question, the kind of flux will change. Not all metals oxidize the same way, so some may not need the same strength of flux. When it comes to silver brazing, a standard flux to use is FB3-A flux. As silver solder and other metals like brass and copper have a high thermal conductivity, there will be less of a chance of oxides forming.
Considering The Filler
When choosing a filler, the flow and melt temperatures must be considered. As the flux will also be melting, you want to make sure you choose the right one. You may have to select a flux that has a range of temperatures that is active like FB3-A or FB3-D. By determining the right kind of flux, you can eliminate the chances of oxidation occurring, especially when it comes to silver solder.
If you are going to be silver brazing for longer at higher temperatures, you will have to choose a flux that can handle this. Some of the high temp fluxes that are most commonly used are FB3-D and FB3-C.
As there are many options to choose from when considering flux, you want to make sure you pick something right for the temperature and kind of metals involved.
