The present invention relates to a fluxing agent for soldering or brazing aluminum components as well as to a method for formulating fluxes.
Assemblies of parts of aluminum or aluminum alloys or in combination with parts of suitable other materials, such as copper, brass, iron or stainless steel can be produced by brazing these parts. Techniques for brazing these components are known. The components are connected with one another by heating with the help of a brazing metal and a flux. Moreover, either the brazing metal can be used separately or components, plated with brazing metal, can be used. Advantageously, fluxes based on complex fluorometallates, such as complex alkali metal fluorides, which free the surface of the components, which are to be brazed to one another, from oxide built-ups, are used. In this connection, the flux is applied either dry or as a paste or as an aqueous suspension on the components, which are to be connected, or the components are dipped in the suspension.
As used herein, the term “flux” refers to ready-for-use compositions, which, aside from the flux, optionally contain additives. However, the flux may consist only of the fluxing agent. Examples of suitable additives which may be contained in the flux preparation include materials such as binders, dispersants, brazing metal, brazing metal precursors, solder-forming materials and/or stabilizers.
Alkali metal fluoroaluminates, alkali metal fluorosilicates and alkali metal fluorozincates are examples of fluxes based on complex fluorometallates, other known fluxes also being suitable. The fluorine compounds may be used as pure compounds or as a mixture of fluorine compounds.
As already stated, the flux or flux preparation is applied dry, as a paste or in the form of aqueous suspensions on the components, which are to be connected. To prepare the suspension, the components of the mixture are suspended in water. Because of the nature of the components, the preparation of the suspension may lead to the formation of dust or to dosing errors.
In order to prepare a paste, the flux is mixed with the additives and carrier substances, such as organic compounds. The viscosity of the preparation can be controlled by the amount of carrier substance.