INTRODUCTION
Soldering and brazing are the processes of joining metal pieces, making use of heat, and a filler metal whose melting point is lower than the melting points of metals to be joined. In soldering, the melting point of solder (or filler metal) is usually less than 427°C, whereas in brazing and braze welding, the melting point of filler metal is higher than 350°C. In soldering and brazing, there is no direct melting of the base metal of workpieces being joined, rather the solder or filler metal flows between the surfaces to be joined through the capillary action. The most common use of soldering and brazing is in joining two dissimilar metals. Differences between soldering and brazing are given in the following:
(a) The melting point of solder or filler metal used in soldering is lower than 427°C, whereas in brazing, the melting point of filler metal is higher than 427°C.
SOLDERING
BRAZING
Brazing is a technique of joining two similar or dissimilar metal pieces together by heating the surfaces and by using a non-ferrous filler metal having its melting point above 427°C but below the melting points of metals to be brazed. The molten filler metal is distributed between the joint surfaces by the capillary action, which on cooling results in a sound joint. The main advantage of brazing process is the joining of dissimilar metals and thin sections. The process i is mostly used for joining pipes and other fittings, carbide tipping on tool shanks, electrical parts, radiator, repair of cast iron parts and heat exchangers.
In brazing, bond is produced by the formation of either solid-state solution (diffusion bonding) or intermetallic compounds of the parent metal (job) and one of the metals in the filler material (brazing alloy). The strength of the brazed joint is provided by metallic bonding.
