Soldering

Soldering and brazing

The secret to soldering, brazing and braze welding is to keep the joint opening small. The smaller the amount of filler metal, the stronger the joint. Soldering and brazing have been widely used for centuries, but the differences between soldering, brazing and braze welding may be less well known.



In soldering, metals are joined with the help of a filler metal with a low melting point, below 450° C, and below the melting point of the metals to be joined. In brazing, the filler metal has a melting temperature of more than 450° and up to 1000° C, and the brazing tool is often a flame. The filler metal is distributed between the close-fitting surfaces of the joint by capillary action. Soldering is used for copper and its alloys, zinc, steel and aluminium and its alloys. The most common filler metal is based on tin, though special filler metals are required for aluminium. Compared to brazing, soldering results in weaker joints. If the filler metal is alloyed with silver, the resulting strength is considerably better. Braze welding is the process of joining metals whereby the melting temperature of the filler metal is above 450° C but below the melting point of the metals to be joined. The filler metal is not distributed by capillary action, but is applied to the joining metals from a welding rod. Braze welding is still used extensively to repair casted parts. Both soldering and brazing can be easily automated. An oxy-fuel flame is often used for soldering and brazing applications, with a fuel gas adapted to the requirements of the process. Working with fuel gases and oxygen can be a risk if the person using the equipment does not have sufficient knowledge of the equipment and its installation.