What is the purpose of flux in the silver brazing process?

Flux plays a critical role in the silver brazing process, primarily aimed at preventing oxidation. When metals are heated during brazing, they can easily react with oxygen in the air, forming oxides that can interfere with the joining process. The presence of these oxides can compromise the integrity of the bond between the base metals and the filler material, potentially leading to weak joints.

By applying flux, a protective layer is created on the surface of the metal being joined. This layer effectively shields the surface from oxygen and contaminants at high temperatures, ensuring that the metal surfaces remain clean and enabling effective capillary action of the liquid filler metal into the joint. This results in a stronger, more reliable bond as the filler material can wet the surfaces it needs to bond to without being hindered by oxidation.

While lubrication may help in certain applications, it is not the main function of flux in this context. Additionally, removing air from the joint and enhancing the color of the metal are not relevant purposes of flux during the silver brazing process.