No single flux works well for all aluminum alloys. Variables which demand different fluxes include differences on oxidation rate, melting and casting temperatures, alloy end use and type of furnace, e.g., induction, reverberatory, etc.
Probably the single most important flux function is the separation of oxides and other dross materials from metallic aluminum. Because aluminum and it's alloying elements are chemically active, oxides, nitrides, carbides and sulfides are readily formed. These oxides and other impurities are carried into the metal during the melting of ingot and scrap. Turbulent transfer, excessive stirring and ladling promote further inclusion of such dross in the cast alloy. Alloys with substantial magnesium content are especially prone to high dross production. Other strong oxide contributors include moisture on charge metal and high proportion of small scrap. Improperly adjusted furnace flames can also result in an atmosphere that will rapidly oxidize molten metal.
Since oxides of aluminum have a higher density than molten aluminum, the oxides would be expected to settle to the bottom of the melt. However, the oxides will frequently contain occluded or trapped gas, thus lowering their density so that oxides remain suspended throughout the body of the melt.
The ready formulation of oxides and other dross impurities and their difficulty of removal make a function of fluxes essential to good aluminum casting. Below is a listing of different types of fluxes.
Asbury Fluxmaster provides a wide range of flux products to the non-ferrous metal processing industry. Metal treatment fluxes are proprietary formulations of primarily inorganic chemicals utilized as consumable products to facilitate and improve molten metal processing. In broad terms, there are four main categories of flux functionality, Drossing Fluxes, Furnace Cleaning Fluxes, Metal Treatment Fluxes, and Specialty Fluxes.
Practically speaking, most fluxes perform in more than one specific application a fact that sometimes tends to blur the boundaries between the broad categories. Asbury Fluxmasters goal is to provide our customers with the flux that is best suited for their specific operations. Our extensive product line includes fluxes designed for calcium removal, magnesium removal, sodium free versions, as well as fluxes designed for the main categories that are tailored to operate most effectively within any given temperature range. Asbury Fluxmaster has the ability to assist the customer in taking advantage of the multifunctional nature of the fluxes to enable the customer to maximize the effectiveness and net value of this often overlooked metal treatment additive.