Brazing

Brazing joins metal components by melting a filler metal above 450°C while keeping the base metals solid. The molten filler flows into the joint, usually by capillary action.

Capillary action: The movement of liquid through narrow spaces driven by surface tension and interactions with surrounding surfaces. It draws molten filler into the narrow clearance between brazed components.
Filler metal: A consumable metal or alloy that melts to join components without being the principal material of those components. Brazing relies on a filler whose melting temperature is below that of the base metals.
Soldering: A metal-joining process that melts filler at or below 450°C while keeping the base metals solid. The 450°C filler-temperature threshold separates soldering from brazing.
Vacuum brazing: A furnace brazing process performed under vacuum to limit oxidation and contamination. It produces clean joints in assemblies where flux residue would be undesirable.
Ancient Egyptian metalworking: The craft traditions used to shape, cast, and join metals in ancient Egypt. Archaeological evidence includes early metal objects assembled using brazing techniques.
Wetting: The ability of a liquid to maintain contact with a solid surface, determined by intermolecular forces. Filler must wet the base metals to spread across them and form a sound joint.
Base metal: The principal metal or alloy forming the components being joined or processed. The base metals remain solid while the brazing filler melts.
Welding: A group of processes that join materials by coalescing them, usually through melting the base material. Unlike brazing, fusion welding melts at least part of the base metal.
Aluminum brazing: Brazing of aluminum components using filler alloys and methods suited to aluminum's oxide layer and thermal properties. Aluminum heat exchangers are commonly assembled by controlled brazing.
Metallurgy: The science and technology of extracting metals, shaping them, and controlling their properties. Brazing developed within the broader history of working and joining metals.

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