Knowledge

Put simply, brazing is the process in which two or more metal items are joined together by pouring a filler metal into the joint. The filler metal fills the gap between the close-fitting parts via capillary action. The filler is brought just above its melting temperature and is typically protected by a flux, such as borax. This flows over the base metal in a process called wetting, and is cooled to join the pieces together. Flux can be applied as a paste, liquid, or powder, and can also be applied via brazing rods. Brazing sheets can play a critical role in this process, serving as a very convenient method for pre-placing filler metal.

Variables such as temperature, vacuum level, and cycle time are strictly controlled during brazing based on the specific materials being used. There are several types of brazing available, including flux brazing and vacuum brazing - two very popular methods.

During flux brazing, flux pours into the joint, which then is dislodged by the liquid filler to remove oxides on the part, completing the braze. Manual and automatic torch brazing, induction brazing, dip brazing, and controlled atmosphere brazing are common types of flux brazing.

Vacuum aluminum brazing, on the other hand, occurs in a vacuum furnace, or can be performed using inert gas atmospheres. With this method, flux is not needed to create joints due to the vacuum’s clean environment. Magnesium is used as an additive - also known as a “getter” - during the vacuum aluminum brazing process.