Braze and brazing alloys join metals or other materials without extensive fusion of the substrates. Brazes have a higher melting point (>800° F) than solders and cause little or no metal vaporization, gain growth, stress corrosion, or distortion. There are six basic types of brazing filler alloys: aluminum alloy brazes, copper alloy brazes, gold alloy brazes, nickel alloy brazes, palladium alloy brazes, and silver alloy brazes. Aluminum alloy brazes and aluminum brazing alloys contain aluminum-based compositions such as aluminum-silicon alloys. Copper alloy brazes and copper brazing alloys contain copper-based compositions along with phosphorous, zinc, manganese, or nickel and boron (Cu-Ni-B.) Braze and brazing alloys that are based on gold, nickel, palladium, or silver-alloy compositions are also commonly available. Vacuum grade brazes and vacuum grade brazing alloys are products with suitably low pressure or low volatility for processing in a vacuum furnace. Cadmium-free brazes and cadmium-free brazing alloys are free of cadmium additions. Cadmium, a toxic metallic element, is just one of the braze and brazing alloys prohibited under the European Union’s (EU) Restriction of Hazardous Substances (RoHS) directive. Specialized braze and brazing alloys that contain controlled amounts of copper and nickel may be suitable for brazing ceramics and other non-metallic materials.

Braze and brazing alloys are available as pastes, powders, preforms, strips, sheets, foil, solid wire or tubular wire. Melting range and conductivity are important parameters to consider. Approvals and conformance are also important considerations. Standards, approval, and conformance organizations for braze and brazing alloys include the American Bureau of Shipping (ABS), the American Society of Mechanical Engineers (ASME), the American Society for Testing and Materials (ASTM), the American Welding Society (AWS), the British Standards Institute (BSI), the Canadian Welding Bureau (CWD), Germany’s Deutsches Institut für Normung, Norway’s Det Norseke Veritas (DNV), the International Standards Organization (ISO). Japanese Industrial Standards (JIS), and the Resistance Welding Manufacturers Association (RWMA). Braze and brazing alloys that meet grade specifications from Lloyd’s Register of Shipping, or that comply with U.S. military specifications (MIL-SPEC) are also available. The Aerospace Materials Specifications (AMS) from the Society of Automotive Engineers (SAE) applies to aerospace and aviation applications.