100c User Manual
48
ch.7
Palladium can be welded using the Orion welder, however, cracking can occur.
Palladium cracking is an especially difficult phenomenon to overcome with laser or pulse arc
welding. If only one weld spot is made, cracking will typically not occur unless the weld joint
is stressed by hammering, etc. is means that welding over porosity in a (Pd) piece can be
accomplished with the Orion to help clean up the metal during the finishing process. However,
welding more than one overlapping weld will inevitably lead to cracking (laser or pulse arc welder).
Palladium cracking can be thought of as a combination of hot cracking and new weld puddle
crystal structure problems. After a weld, the molten (Pd) re-crystallizes, typically forming a large
and weak metal grain structure. When welds overlap, the new crystal structure in the last weld
puddle is weak compared to the original metal. e result - a crack will start at the edge of the
new weld where it overlaps with the old weld joint as the new weld cools and is stressed. e
crack will then run along the middle of the weld puddle in the direction of the overlapping joints.
is cracking is due to the stresses created during the weld puddle cooling process as described
above with hot cracking. However, this time instead of geometry causing the cracking, a rip starts
in the old crystal structure and propagates during the cooling process, much like ripping a piece of
paper. e result – (Pd) is difficult to weld successfully without breakage. Typically, single spots
of porosity can be welded and fixed but overlapping welds will crack.
ere is a welding solution that can stop this cracking process. e addition of gold fill wire to
the weld joint creates a new alloy and stronger crystal structure. e gold can discolor the weld
joint. However, by welding over the joint several times the gold will diffuse into the (Pd). Another
possible solution is to use a high gold content white-gold (Pd) alloy laser wire.
Silver (Ag)
Silver is an interesting metal with several properties that must be considered during the welding
process. First, silver is highly reflective over a large range of light wavelengths. is metal
characteristic makes welding silver difficult for a laser, but poses no problems for a Pulse Arc
welder. Second, silver is a very mobile metal when in a liquid state and has low surface tension
when compared to other metals. Because of these properties, how the weld energy is applied to
silver is important.
When welding silver it is important to understand the concentration of your weld energy relative
to the size of the silver being welded. For very small welds, a sharp electrode poses no problem.
is means that in the Orion’s arc mode, silver will typically behave well even with a concentrated,
focused beam of energy (i.e. a very sharp electrode tip point). However, as the desired spot size
gets larger (bigger arc mode welds and almost all pulse arc mode welds) the liquid silver is easily
pushed around by the welding pulse. is will lead to large blobs of material being displaced
from the weld site resulting in a noticeable hole. To avoid this problem, simply un-focus the weld
energy by creating a truncated electrode tip flat. e size of the flat depends on the size of the
weld. For relatively small welds a small flat is all that is required. For very high energy welds the
electrode may be completely flat (1mm diameter).
Resistance welding silver in tack mode is very difficult because of silver’s high electrical
conductivity. Sterling silver has a high electrical conductivity very similar to that of copper.
However, Argentium silver is approximately 30% less conductive. is means that more heat
can be generated during the spot welding process due to the additional material resistance. Use
Argentium silver if your application requires spot welding as opposed to pulse arc welding. Even
while pulse arc welding it may be desirable to use Argentium silver because of its superior tarnish
resistance. in Argentium silver parts can be welded directly using copper electrodes. icker
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