The definition of brazing is to join two or more pieces of metal by means of flowing a filler metal between the joint interfaces at a temperature below the melting point of the base metal but above 840°F.
The filler metal, upon cooling to the solid state, forms a strong metallic bond throughout the joined area.
What Is Aluminum Dip Brazing Made Of?
In aluminum dip brazing the filler metal is basically 88% aluminum and 12% silicon.
What Does Assembly Look Like?
The parts to be brazed after being chemically cleaned, are assembled with the filler metal pre-placed in or as near the joints as possible. Capillary action will cause the filler metal to flow into the joint (gap) between the assembled pieces.
The assembly is then preheated in an air furnace to insure uniform temperature of dissimilar masses in the assembly. The assemble is then immersed in (the brazing flux) a molten salt bath.
The bath is maintained at 1,095°F±5°F in the dip braze pot or what is called a salt bath furnace. As the assembly is immersed or dipped, the molten flux encounters all surfaces removing oxides and providing heat transfer for braze metal melting. This liquid heat (brazing flux) is extremely fast and uniform. The time of immersion is determined by the mass to be heated but is seldom over two minutes in duration.
Upon removal from the bath, the brazed assembly is placed in a flux drainage area and allowed to cool.
Since the bath is a flux, complete bonding on oxide-free surfaces assures unusually high-quality joints. After brazing the assembly will need cleaned and may need hardened or tempered depending upon the material and specifications.
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