Abstract: A method for repairing and joining aluminum alloy articles and structures, such as heat exchangers for use in automotive applications. The method utilizes a flux-coated soldering rod (10) that is used to deliver a solder alloy (12) and a flux compound to a region to be repaired. The flux compound has a higher melting temperature than the solder alloy (12), and is present as a coating (14) that sufficiently thermally insulates the alloy (12) to cause the flux compound and the solder alloy (12) to melt nearly simultaneously during the soldering operation. The solder alloy (12) is preferably a zinc-aluminum alloy, while the flux coating (14) preferably contains a cesium-aluminum flux compound such as potassium cesium tetrafluoroaluminate, dispersed in an adhesive binder that will readily volatilize or cleanly burn off during the soldering operation.

Abstract: A method for repairing and joining aluminum alloy articles and structures, such as heat exchangers for use in automotive applications. The method utilizes a flux-coated soldering rod (10) that is used to deliver a solder alloy (12) and a flux compound to a region to be repaired. The flux compound has a higher melting temperature than the solder alloy (12), and is present as a coating (14) that sufficiently thermally insulates the alloy (12) to cause the flux compound and the solder alloy (12) to melt nearly simultaneously during the soldering operation. The solder alloy (12) is preferably a zinc-aluminum alloy, while the flux coating (14) preferably contains a cesium-aluminum flux compound such as potassium cesium tetrafluoroaluminate, dispersed in an adhesive binder that will readily volatilize or cleanly burn off during the soldering operation.

Abstract: An improved flux composition is provided which is formulated for use in the brazing of aluminum alloy components, such as in the assembly of brazed heat exchanger units used in automotive applications. The flux composition is in a concentrated form, permitting its selective application to the joint surfaces of a heat exchanger's subcomponents, and contains a flux material which consists essentially of potassium tetrafluoroaluminate, a carrier system such as a glycerol-ethylene glycol system, a binder, and a liquid medium such as water. Most preferably, the potassium tetrafluoroaluminate constitutes at least about 96 percent of the flux material, and the binder is xanthan which substantially prevents the flux composition from separating during storage. The flux composition does not contain potassium aluminum fluoride.

Abstract: The present invention utilizes a novel flux-coated alloy member that is particularly adapted to be selectively positioned at the braze joints of a tube-and-center type heat exchanger. The flux-coated alloy member is suitably sized and shaped to place a predetermined quantity of flux compound and brazing alloy at the braze joints, so as to avoid the presence of excess flux compound and brazing alloy which may otherwise have a detrimental effect on the quality of the braze joints subsequently formed during a brazing operation. The flux coating of this invention is hard and durable, and is composed of potassium tetrafluoroaluminate particles which are dispersed in either a natural resin or a water soluble epoxy resin.

Abstract: An improved method of making high quality potassium tetrafluoroaluminate. Hydrofluoric acid is added to high purity aluminum metal powder to form aluminum fluoride in solution. Nitric acid is added to this solution whereby impurities in the solution dissolve into the nitric acid. Water is then added to the solution to precipitate from the solution solid aluminum fluoride with impurities removed therefrom. The aluminum fluoride is then milled in the presence of hydrofluoric acid and potassium hydroxide whereby the exposure thereto produces the high quality potassium tetrafluoroaluminate which may then be washed and dried.

Abstract: A brazing paste for aluminum or aluminum alloy parts. The paste consists essentially of, by weight, between about 8 and 72 percent potassium tetrafluoroaluminate having a purity of at least about 96 percent, between about 15 and 75 percent aluminum-silicon alloy, and between about 2.5 and 50 percent organic carrier having a vaporization temperature which is below the melting temperature of the aluminum-silicon alloy, and the melting temperature of the potassium tetrafluoroaluminate being below the melting temperature of the aluminum-silicon alloy. The high purity potassium tetrafluoroaluminate has a lower melting temperature so that a greater number of aluminum-silicon alloys may be used therewith and does not have corrosive substances so that the braze can be of high quality and not require additional steps of washing and drying the brazed part for overall cost savings.