At present, aluminum alloy fluxes are mainly divided into two systems: NaCl-KCl system and KCl-MgCl2 system. The former contains Na and equimolar NaCl-KCl forms a low melting point eutectic at 665°C, which has a strong wetting effect on Al2O3. Generally used in alloys that are not sensitive to Na elements, it is the basis of most fluxes; the latter, as Na-free flux, is the basis of aluminum alloy fluxes with high Mg content. KCl-MgCl2 forms a low melting point at 424~465℃.
In order to increase the separation effect of slag and aluminum, improve the surface tension of the flux and improve the purification ability of the flux, additives such as Na3AlF6 or K3AlF6, CaF are added on the basis of the flux. The addition of these additives is generally divided into mechanical mixing and remelting mixing, and the uniformity of the remelting mixed flux composition is far better than that of mechanical mixing and can obtain low-melting eutectic, but the cost is correspondingly higher. Used for the preparation of high-performance flux. The basic premise of the remelting mixing method is to master the thermodynamic properties of the mixture, and then to ensure the melting point of the flux. Generally, the melting temperature of the flux must be lower than the melt temperature during aluminum smelting by more than 50℃. The molten flux is used to achieve the adsorption and melting of impurities. To remove the slag ability, if the melting point cannot meet the requirements, a heating agent needs to be added to promote the rapid temperature rise of the flux, which will complicate the composition of the aluminum alloy fluxes.
The simplification of aluminum alloy refining flux composition is one of the current development trends in flux preparation, and efficient purification is achieved through the simplest physical and dynamic characteristics. Therefore, to evaluate the quality of flux, we must first examine the simplicity of flux composition.