Brochure

PH: 513-754-2000
THE HARRIS PRODUCTS GROUP
www.harrisproductsgroup.com
12
PH: 513-754-2000
THE HARRIS PRODUCTS GROUP
www.harrisproductsgroup.com
13
The outside of the joint is hot, but the inside
is not up to brazing temperature.
Review correct heating procedure on page
9. Remember to heat the tube first to
conduct heat inside the fitting.
There is a flux breakdown due to excessive
heat. If overheated, the flux can become
saturated with oxides and the brazing alloy
won’t flow. Try using a softer flame and/or
applying a heavier coating of flux. On thick
sections where heating is prolonged, or on
stainless steel, Harris Stay-Silv
®
black flux
is recommended.
Review heating techniques:
(a) The base metals are not up to brazing
temperature, and the alloy has been melted
by the torch flame.
(b) The joint has been overheated and the
flux is no longer active.
Base metals have not been properly cleaned.
Make sure fitting is up to temperature and
the flame is directed towards the fitting.
When brazing dissimilar metals,
the different coefficient of
expansion may put the filler metal
in tension just below the liquidus
temperature during cooling. This
sometimes occurs in a copper-to-
steel joint. The copper expands
and contracts at a greater rate
than the steel. Brazing alloys are
stronger in compression, so a
steel-to-copper assembly would
help alleviate the problem.
Brazing steel (or other ferrous
metals) with an alloy containing
phosphorus can lead to formation
of a brittle phosphide, that is
prone to cracking. Braze ferrous
metals with non-phosphorus
content alloys.
Excessive joint clearance can
lead to filler metals cracking
under stress or vibration. Make
sure clearances are held to .002”
- .006” at brazing temperature
(depending on alloy).
Too rapid quenching can
sometimes cause cracking. Let
joint cool more before washing off
flux residue.
90% of “leakers” in service
are due to incorrect brazing
techniques. The most common
causes are:
Improper or uneven heating
of joint. The effect of this is
inadequate or incomplete
penetration by the filler metal.
Review proper techniques on
page 9.
Overheating, causing volatilization of
elements (phosphorus, zinc, etc.).
Incorrect torch flame adjustment,
leading to deposition of carbon or
causing excessive oxidation.
Pinhole leaks in copper-to-copper
joints brazed with phosphorus/
copper or phosphorus/copper/silver
filler metals can often be repaired
using Blockade
®
. If care is taken, you
can re-braze the joint with Blockade
®
without re-melting the original braze.
Clean thoroughly before brazing.
We DO NOT recommend brazing
over joints previously soldered with
tin/lead solders. The low melting
elements in the solder may prevent
proper filler metal / base metal
alloying.
Pinhole leaks in joints brazed with
either the phosphorus or high silver
alloys can usually be repaired with
Stay-Brite
®
solder. Clean the joint
thoroughly before soldering and use
Stay-Clean
®
liquid flux.
TROUBLESHOOTING
12
1
2
1
2
1
2
3
4
TROUBLESHOOTING FOR
BRAZING PIPE AND TUBING
TROUBLESHOOTING FOR
BRAZING PIPE AND TUBING
1
2
3
The art of brazing is relatively simple, and the rules of common sense apply.
Occasionally, however, things do go wrong, and the brazing process fails to
do its job satisfactorily. The check lists below have been prepared to assist
in such instances. They are intended to provide practical tips on what to
what to look for and steps to correct them.
IF BRAZING ALLOY DOES NOT FLOW INTO THE
JOINT, EVEN THOUGH IT MELTS AND FORMS A
FILLET
IF BRAZING ALLOY DOES NOT WET SURFACES BUT
BALLS UP INSTEAD OF RUNNING INTO THE JOINT
1
IF BRAZING ALLOY FLOWS AWAY FROM INSTEAD
OF INTO THE JOINT
IF THE FILLER METAL CRACKS AFTER
IT SOLIDIFIES
IF JOINT LEAKS IN SERVICE
REPAIR OF LEAKS