Table 1 is a survey of currently used
soldering compounds for brazing BÖHLER
carbide tips which influence to some
extent the applicability of brazed
tools. In most cases, the soldering
compound is electrolytic copper which
possesses very good ductility. For
tools exposed to very high temperatures
during service, we recommend Cu-Ni
solders. Brass and high-melting silver
solders are used when the shank is
to be hardened from brazing temperature.
Stress and distortion sensitive carbide
tips are brazed with low-melting silver
solders, whose freezing point is below
the transformation temperature of
the steel grade used for the tool
bony. Silver somers are also usen
in combination witv a copper foil
in the seam. This so-called "sandwich"
brazing produces a laminated brazing
seam, with silver solder connecting
the copper foil to the steel shank
on one side and to the carbide tip
on the other. Thus, both the low brazing
temperature of the silver solder and
the high ductility of the copper foil
can be utilized ann combine to form
a low-strees seam. Soft solders permit
a distortion and stress free brazing
of carbide tipped tools and wear parts,
provided the carbide faces to be brazed
are copper coated. However, suchionts
will not resist any serious mechanical
orthermal stresses.
To guarantee a satisfactory brazing
seam, the faces to be soldered must
be bright and clean. This is achieved
by means of fluxes or inert gas that
prevent oxidation of the solder and
the faces to be loined ant reduce
oxide films already formed. Borax
covers the temperature range above
750°C, soldering solution the
range below 500°C, for temperature
in between we recommend special fluxes
available from solder manufacturers.
Designation
Flux
Melting
Range (C)
Working
temperature (C)
Shearing
strength kg/mm2
Application
Cu-Ni
Solder
Cu %75; Ni %20
Borx
1150-1220
1250
23-28
Tools
designed for extreme mechanical and
thermal stresses
Electrolytic
copper
Borax
1083
1120
20-22
Standard
brazing materials for tools to support
high cutting forces and temperatures.
Hard
solder
L-MS 60
DIN 8513
Borax
890-900
900
16-20
For
shanks that must be heat threated
from the brazing temperature and for
average loads
Hard
solder
L Ag 27
DIN8513
special
flux
680-830
850
25-30
Hard
solder
L Ag 49
DIN8513
special
flux
625-705
730
25-30
Carbide
grades where stress is critical or
tools with a tendency to distort
Compound
Ag-Cu-Ag
special
flux
670-690
690
15-30
Hard
solder
(sert lehim)
L-Ag 40 Cd
DIN8513
special
flux
595-630
650
17-22
Soft
solder
(Yumþak lehim)
L-Sn 50 Pb, DIN1707
solderin
solution
183-214
250
3-5
For
almost distortion-free brazing and
for the lowest loads and temperatures
Brazing
Carbide Tips
