hello everyone welcome to Hua Guang's brazing demo video
series in today's video we are going to show
you how to braze copper to copper with Hua Guang's
BCuP-2 brazing rods copper and phosphorus are the two main elements in
copper phosphorus brazing alloys it comes mostly in rod flat rod and ring
shapes this type of brazing alloy is widely
applied in the brazing of copper and copper alloys
especially in the HVACR industries they have good fluidity and an
economical price which contribute to their popularity
today we are going to focus on AWS BCuP-2
which is one of the most typical copper phosphorus brazing products
its phosphorus content is relatively high in the 7.0 to 7.5 percent range
because of this high phosphorus content their melting point is low
in the 710 to 793 ºC (1310 to 1459.4 ºF) range and their fluidity is quite good as you
may know this brazing alloy has self-fluxing
property which means that we don't need to add any flux during brazing
at Hua Guang we produce BCuP-2 in many different shapes
such as rod flat rod and ring the one you see here is a flat rod with the
diameters 1.3 by 3.2 by 451 millimeters
in today's demo our joint design include t-joint and socket joint
and we are going to use flame brazing to braze copper and copper
to ensure we have a high quality and strong braze we need to pay attention to
gap width of each kind of joints gap width needs to be in the 0.05 to
0.25 millimeter range when we design socket
joint we need to avoid the inclusion of any
blind holes before brazing we must clean the oxides
and grease from the surface of base metals and brazing alloy
we are going to use sandpaper to polish the surface first
then use acetone alcohol or carbon tetrachloride organic solvent to clean
them with the aid of ultrasound something to remember though is that
keeping a slight level of roughness on the surface of the base metals
is good for the flow of molten brazing alloy and it allows brazing alloy to
fill the gaps more efficiently then we move on to assemble the joints
and fix them in place so as to ensure that the gap width of
the joint is suitable and also uniform as we can see in the demo we choose
flame brazing as it is straightforward in terms of equipment selection
and also gives us a high level of flexibility
the flame we use here is acetylene and oxygen flame
we can classify the flame into neutral flame carbonized flame
and oxidized flame based on the ratio of oxygen and acetylene in the mixture
we don't recommend carbonized flame and oxidized flame
because if we choose carbonized flame soot will be released during the burning
process which will negatively affect brazing
performance whereas if we choose oxidized flame
oxidation of the base metals will speed up
which will in turn obstruct solder's flow and wetting process
therefore we use neutral flame and we use the outer flame to preheat and heat
the designated area BCuP-2 is a self-fluxing brazing
product the phosphorus content in the alloy
fulfills the role of a deoxidizer so we don't need to use any flux we
repeatedly point our brazing torch from side to side
on the heating area so that we won't overheat a particular spot
flame is to be kept at a 45 degree angle position with the length of the copper
part for most kinds of joints with the exception of socket joint where
flame is to be kept level with bell mouth of the tubing
when we see that the copper base metal is turning light red
it is an indicator that preheating is sufficient and we can add our
BCuP-2 brazing alloy on the opposite side of the flame
something to be noted when we braze tubings sometimes we need to switch the
heating position of the flame symmetrically to the opposite side of
the tube so that the brazing filler metal can
fill every spot of the gap in the brazing process flame is used to
melt BCuP-2 brazing alloy and the molten alloy
then wet the copper base metals under capillary action molten brazing
alloy fill the gap at the braze joint and it dissolves and diffuses with the
copper afterwards allow it to be air-cooled and
solidify for a while and joining of the base metals is now
completed we put it into the water bath after
taking it out we use a towel to wipe any slag on the joint
then we use an air blower to blow it using cool air
so that it won't be corroded afterwards for these brazed parts we need to run
some relevant testing to ensure that they meet our specific
application requirements some applicable tests for the joints include appearance
inspection and metallographic observation for
microstructure analysis a good joint should not have any defects
such as slag inclusion pinhole crack and insufficiency in
brazing and metallurgical bonding with the base
metal should be optimal for socket joint we will do penetration
inspection and if needed we'll also test its
tightness to recap we used the common BCuP-2
brazing alloy in flame brazing to braze copper and copper
using t-joint and socket joint the most important things to remember
are the brazing steps first clean the copper parts secondly
assemble and fix the parts in place thirdly preheat and heat the copper with
flame fourthly molten BCuP-2 then wet the
base metals and fill the joint lastly clean the brazed parts and run
the required testing thanks for watching Hua Guang supplies
thousands of specifications of brazing products worldwide
for more information please visit our website
huaguangwelding.com