— Soldering and Brazing processes differ from welding in the sense that there is no direct melting of the base metal (s) being joined.
— Rather, the brazing or soldering filler alloy flows between the two closely adjacent surfaces of the workpieces by capillary action.
— Both soldering and brazing processes are particularly useful for joining two dissimilar metals.
— Both, the brazing alloy or the solder have lower melting points than the metals to be joined.
— In order to obtain a satisfactory brazed or soldered joint, it is necessary for the filler alloy to
(i) wet the base metal,
(ii) spread and make contact with the joint opening,
(iii) be drawn into the joint by capillary action
— Brazing and soldering processes differ in the following way:
(i) Filler metal used in soldering has a melting point below 800°F (427°C) whereas that in brazing has a melting point above 800°F (427°C).
(ii) The extent of diffusion. In brazing process, bonding conditions are set up so that a large amount of diffusion will take place in order to strengthen and improve the bond, whereas in soldering, diffusion is secondary in importance.
(iii) Brazing produces joints stronger than those made by soldering and they can be used in service at higher temperatures.