In arc welding, fluxes are formulations that, when subjected to the arc, act as a cleaning agent by dissolving oxides, releasing trapped gases and slag and generally cleaning the weld metal by floating the impurities to the surface where they solidify in the slag covering. The flux also serves to reduce spatter and contributes to weld bead shape. The flux may be the coating on the electrode, inside the electrode as in flux cored types, or in a granular form as used in submerged arc welding.

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