Flux (metallurgy)

In metallurgy Flux is an aid to melting; a material which by its chemical action facilitates soldering or brazing of metals. Such a flux applied to a metallic surface cleans it and renders it receptive to amalgamation with the solder or brazing metal. Some fluxes are ammonium chloride or rosin, for soldering tin; hydrochloric acid ans Zinc chloride for galvanized iron and other zinc surfaces; and borax, for brazing.

A related use of the term flux is to designate the material added to the contents of a smelting furnace or a cupola for the purpose of purging the metal of impurities, and of rendering the slag more liquid. The flux most commonly used in iron and steel furnaces is limestone, which is charged in the proper proportions with the iron and fuel. The slag is a liquid mixture of ash, flux, and other impurities.