Brazing, not to be confused with Braising, is a joining process whereby a non-ferrous filler metal and an alloy are heated to melting temperature (above 450°C) and distributed between two or more close-fitting parts by capillary action. At its liquidus temperature, the molten filler metal interacts with a thin layer of the base metal, cooling to form an exceptionally strong, sealed joint due to grain structure interaction. The brazed joint becomes a sandwich of different layers, each metallurgically linked to each other. If silver alloy is used, brazing can be referred to as Silver Brazing. Colloquially, the inaccurate terms "Silver Soldering" or "Hard Soldering" are used.

In the more common, more specific usage, brazing is the use of a bronze or brass filler rod coated with flux, together with an oxyacetylene torch, to join pieces of steel. The American Welding Society prefers to use the term "Braze Welding" for this process, as capillary attraction is not involved.

A variety of alloys of metals, including Silver, Tin, Zinc, Copper and others are used as filler for both processes. There are specific brazing alloys and fluxes recommended, depending on which metals are to be joined.

In order to work properly, the base metals must be exceptionally clean and free of oxides. In most cases, flux is required to prevent oxides from forming. Some metals, such as Titanium cannot be brazed.

Brazing is similar to soldering but higher temperatures are used and the filler metal has a significantly different composition and higher melting point than solder.

Brazing is different from welding, where even higher temperatures are used, the base material melts and the filler material (if used at all) has the same composition as the base material.

The "welding" of cast iron is usually a brazing operation, with a filler rod made chiefly of nickel being used although true welding with cast iron rods is also available.

With all things being equal, brazed joints are stronger than soldered joints but weaker than welding.

Brazing processes

• Block Brazing
• Diffusion Brazing
• Dip Brazing
• Exothermic Brazing
• Flow Brazing
• Furnace Brazing
• Induction Brazing
• Infrared Brazing
• Resistance Brazing
• Torch Brazing
• Twin Carbon Arc Brazing