BRAZING FLUX POWDER FOR ALUMINUM-BASED MATERIAL AND PRODUCTION METHOD OF FLUX POWDER

摘要

It is aimed at providing a brazing flux powder, which exhibits an excellent spreadability in case of brazing of an Mg-containing aluminum-based material, which is non-corrosive and is thus excellent in safety, which is relatively inexpensive and is thus economically excellent, and which can be used in a wide and general manner. There is provided an improvement in a flux powder containing therein KAlF₄, K₂AlF₅, and K₂AlF₅·H₂O, usable for brazing of an aluminum-based material having an Mg content of 0.1 to 1.0 wt %, and the improving characteristic configuration resides in that the flux powder has a composition where a K/Al molar ratio is within a range of 1.00 to 1.20 and an F/Al molar ratio is within a range of 3.80 to 4.10, and the K₂AlF₅ and K₂AlF₅·H₂O have a sum content of 6.0 to 40.0 wt %, balance KAlF₄, and that part or the whole of the crystal structure of K₂AlF₅·H₂O is at least one of a K-defective type, F-defective type, and K-and-F-defective type crystal structure.