Brazing flux
Fluxes dissolve oxides and protect the filler metal during brazing to ensure defect-free wetting.
Physicochemical Mechanism of Action
Fluxes are chemical aids that dissolve oxides on the metal surface. They form a protective slag layer that keeps the filler metal away during heating and brazing. This prevents oxides from blocking the filler or impairing its fluidity.
Metallurgical Relevance & Risks in Welding
Without flux, oxides can contaminate the surface of the part to be brazed and dirty the filler metal. This leads to porosity, incomplete wetting, and poor brazing results. A missing or insufficient flux can also cause the filler to not flow well onto the surface, leading to uneven distortion of the part or even a failed joint.
Workshop Practice & Instructions
Use flux in the right amount before brazing. Usually a 1:10 ratio between flux and metal is used. Apply the flux with a brush or nozzle onto the surface to be brazed and let it sit for a few seconds before applying the filler. Make sure the surface is dry before letting the filler flow.