60
12.7.10 Checking of brazing (insert) points
1. No impurity on the brazing point
If dirt or oil is attached on the brazing point, the
brazing filler metal does not reach to junction, and
it may cause poor welding.
2. Adequate gap space in the brazing point
The advantage of capillary current situation is
used in brazing. If the gap space is too large, this
phenomenon may not occur and it may cause
poor welding because brazing filler metal does not
flow to join the front part.
3. Appropriate size for insertion
The guideline for pipe insertion dimensions is to
three times the diameter of the base material, but
you need to decide the insertion size in
consideration of the clogging of the brazing
material. Generally, for thin pipes, you need to
increase the insert size, and for thick pipe vice
versa.
4. Brazing material to flow from top to bottom
Brazing filler metal will easily flow to the
connecting portion by capillary action.
Further, by bending the brazing portion of [dryer
side] of the capillary tube at 15 mm from the tube
top to the angle of about 120°, you can prevent
the damage of dryer inside and the clogging of
brazing material caused by the excessive insertion
of capillary tube.
Gap 0.025 ~ 0.05 mm
Insert diameter 10 ~ 25 mm
Inner diameter ø6.45
Outer diameter ø6.35
Brazing material
(Runny)
Brazing material
(Hard to flow)
Dryer
15 mm
120°
Filter
(Wire mesh)
Capillary
tube
12.7.11 Brazing and heating
1. Place the flame to a pipe which has more heat
capacity in order to let the brazing material melt by
the pipe heat. Heat the pipe up to the melting
temperature of the brazing material, but when it is
overheating, assess the temperature by pipe color
in order not to melt the pipe.
Burner
Burner
Brazing
material
Brazing
material
The pre-heating is to heat the base material until the melting temperature, and requires certain training to distinguish
the color of the heated base material in order not to melt the material.
The color and temperature of copper tube
Becoming red color • • • • • • • 480°C
Dull red • • • • • • • 650°C
Cherish red • • • • • • • 760°C
Brightening cherish red • • • • • • • 870°C
