アルミニウムブレージングにおける母材酸化膜の除去過程と溶融フラックスによる反応ろう接について
1973 年 37 巻 1 号 p. 94-99
詳細
1973 年 37 巻 1 号 p. 94-99
It is indispensable for the aluminium joint by soldering or brazing to remove the oxide film from base metal with a caustic flux. The process of oxide removal in aluminium brazing has been studied in terms of changes in the electrochemical potential of a cell set up between the oxide-coated aluminium plate and platinum in molten brazing flux. Measurements of the potential of the oxide-coated aluminium during the course of the fluxing action show that the rate of potential change is related to the flux efficiency. In this experiment the effects of fluoride addition to the LiCl-KCl system brazing flux on the fluxing action were examined.
Joining aluminium by reaction soldering also has been carried out to apply a replacement reaction between aluminium base metal and metal chlorides such as zinc-, cadmium- stanous- and lead-chlorides in molten flux. The results obtained are as follows:
(1) The flux efficiency was affected by kinds and contents of fluoride added to the LiCl-KCl base flux. Additions of alkaline and alkaline earth metal fluorides to the LiCl-KCl base flux make the flux efficiency higher than aluminium fluoride and cryorite.
(2) The oxide films are nearly completely removed from the aluminium base metal by dipping for 4 sec in the flux containing 3% sodium fluoride.
(3) The metal deposition on the aluminium base metal from the molten flux containing metal chloride is influenced by the reaction temperature and the concentration of metal chlorides. The metals deposited on the aluminium base metal flow rapidly as the filler metal to form fillets when the reaction temperature is higher than the melting points of deposited metals.
(4) The molten deposited metals of high flowability are zinc and tin, and flow factors of these metals indicating brazability, the ratio of the volume of the deposited metal to the volume of formed fillets, are larger than 1.0 at higher temperature. In case cadmium and lead which can hardly be alloyed with aluminium as the deposited metals, however, the flow factors are smaller than 1.0 usually.
