Characteristics of CsF-AlF{sub}3 system non-corrosive flux for brazing of aluminum

摘要

To investigate the brazing characteristics of three CsF-AlF{sub}3 non-corrosive fluxes for aluminum, fillet formation test has been performed using magnesium containing base metal and zinc containing filler metals. The brazeability was evaluated by the length of formed fillet on tee-type joint and penetration depth of flux into magnesium containing base metals. The increase in magnesium content of base metal deteriorated the brazeability in all fluxes. The CsF-AlF{sub}3 fluxes showed inferior brazeability to KAlF{sub}4-K{sub}2AlF{sub}6 flux, however, one of the CsF-AlF{sub}3 flux with mole fraction of CsF/AlF{sub}3=1.2 (CA flux) gave similar brazeability and narrower flux penetration depth for magnesium containing base metal. Brazeability and flux penetration depth were closely related to fluorine content per unit mole of flux, the increase of fluorine content enhanced fillet formation, however, it enhanced penetration simultaneously. The CA flux offered excellent brazeahility for zinc containing filler metal, whereas KAlF{sub}4-K{sub}2AlF{sub}6 flux showed poor brazeability in filler metal more than 5Zn. The use of CA flux is recommended for brazing of magnesium containing base metals and zinc containing filler metals.