Brazing is a heat treating process in which melted metallic filler is used to bond two base pieces creating an extremely strong and often hermetic joint. Unlike many heat treatments, brazing does not alter the internal structure of materials in order to effect change. Instead, brazing uses a technique similar to welding and soldering in order to create strong and lasting joints between two components.
This particular heat treating process involves heating two adjacent metal parts to just below their melting points. The brazing material, or filler is then melted along the heated seam between components. This filler blocks in the entirety of the gap and creates a strong seal when cooled. Industries such as aerospace, agriculture, semiconductor manufacturing, plumbing and others rely on the use of brazing to join panels, pipes, tubes, rods or any additional components which are not, but should be adjoined. Metals such as copper, bronze, steel, aluminum, iron and stainless steel can be joined to similar elements or to any other metal without the distortion, deformation or chemical amalgamation encountered by other heat treatments. Ceramics and other non-metal materials can be joined via brazing with specialized materials and attention, though this is far less frequent. No matter the materials, safety precautions are essential to workplace and employee safety in facilities where brazing is performed. Tinted goggles and heat resistant gloves are most commonly used, though a welding mask and full suit may also be required in some applications.
There are several different types of brazing. Categories based on the technique used to build the joint include furnace brazing, torch brazing, dip brazing and vacuum brazing. Torch brazing is by far the most common. An acetylene or hydrogen fueled torch is used to heat the base metals near the joint. These substrates should be heated but not melted. The filler, however, is placed along the seam of the joint and melted. For convenience fillers are available in rod, ribbon, powder, paste, cream and wire form. Furnace brazing is another popular option and is better suited to mass production. Parts or panels are clamped together and then placed in the oven or on a conveyor belt that will run them through the furnace. The filler is already in place so that when the assembly encounters heat, it melts into the crevice. Vacuum heat treating often uses the method of brazing. Vacuum brazing is very similar only the parts are heated in a vacuum environment thereby eliminating the possibility of contamination. Dip brazing also excludes air, making it and vacuum techniques popular for use with metals such as aluminum which might otherwise form oxides. Dip methods are just as they sound, the parts are joined and the filler applied before the entire unit is dunked into a bath of molten salt. In addition to categories based in method, other groupings are classified by the material used as the filler. Silver, copper, nickel, palladium, gold and aluminum brazing are widely available and appropriate for most brazing applications.