| Abstract: |
Removal behavior of oxide film, on the surface of Al-12Si filler of the gap filling specimen, by usual brazing flux was investigated using In-situ brazing observation furnace. Brazing was carried out under N2 gas atmosphere with low O2 concentration and dew point. Flux was painted only on the filler surface. Below the solidus temperature of Al-12Si filler, flux started to melt at its melting point and penetrate between oxide film and matrix from the crack of the film. At the solidus temperature, 577, oxide film was broken into pieces and floated over the liquid phase filler metal. However, the broken film remained on the liquid filler metal and seemed that it was not chemically dissolved by flux. At the same time, surface oxide film of the brazed material, 3003, was also broken by flux reached ahead of the liquid filler metal. Then filler progressed under the remained oxide film of 3003. Therefore, it was considered that flux did not chemically dissolve the surface oxide film itself, but electro-chemically attacked the matrix just beneath the film and released the film from the matrix as the main reaction, then led to successful brazing.
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