Brazing is one of the joining method wherein coalescence is produced by heating in
a suitable temperature and by additional using a filler metal and having a liquidus
temperature above 4270C and bellow the solidus temperature of base metals.
In braze process the metallic parts are joined by a non-ferrous filler metal or alloys.
The filler metals are distributed through the closely fitted mating parts and joint
by the capillary action force. Brazing is the semi-permanent joint, whereas welding
is permanent joint.
Principle of brazing operation:
There are not necessary to melt the base metal. In brazing process comparatively
the low melting point filler metals are used against the base metal. The joint operation
will be success while the base metal pieces are cleaned and free from oxides, oils,
The braze filler metal wets the base metal surfaces and spreads along the consecutive
joint surface with the capillary action. Here the capillary action force is plying
major part of rolls to producing good quality of brazing joint.
For the brazing process doing smoothly the fluxes are used additionally, which is
cleaned the metal surfaces and provided the wet properties to the base metal surface.
Due to the capillary attraction between the base metal and filler metal is much times
higher than that between the fluxand brazing base metal. In the brazing process
the fluxes are thrown away and filler metals are flows into the very tiny gap of
mating parts or by the capillary attraction the joint is produced. While the gap
of mating parts are too small, the capillary attraction flow will be better.
Remember this— the high fluidity of molten filler metal is the important factor in
obtaining successful brazing joint.
How to braze:
In brazing operation following the steps -
Prepare the braze work piece and clean the joint portion and cleaned also filler
Provide the flux to the both base metal joint portion and filler metal surfaces.
Fitting or aligning the base metal parts to be make joint.
Pre-heat the hole base metal, when the material has high heat conduction rate.
Heating up the joint portion of base metals.
Applying the filler metal on to the joint and flux may be applied if needed.
Cooled the brazing joint in room temperature.
Cleaning or removing the flux residue from the brazing joint.
Brazing filler metal properties:
It has to ability wet the base metal and make the strong, sound bond joint.
Maintain the proper melting point temperature and flow properties which allow the
filler spread through the joints and prepared capillary action smoothly.
It must desirable mechanical and physical properties of joints, like strength, ductility,
Advantages of brazing joints:
Gas entrapment is very less, because the filler metal melt properly and spread through
out surface and make pressure tight joint.
Brazing joint can be carried in large number of dissimilar material.
Varieties thickness of material can be joint easily.
Complex and multi-component assemblies are joint together in very economically.
Brazing can maintain close tolerance for precision joint.
Smooth surface or scale less surface can be obtained.
The joints posses good strength at the increased temperature.
Thin walled sheets or light gauge sheets easily joint by brazing, which can not
joint by welding.