16
MELTING AND CASTING PROCESS
MELTING AND CASTING OF CHROME -COBALT MOLYBDENUM WITH HIGHLY
RESISTING SILICON NITRIDE CERAMIC CRUCIBLE REF. A100.481 OR WITH
CERAMIC CRUCIBLE A100.425 CAP. 100 GR.
Chrome-Cobalt Molybdenum alloys melt differently from precious alloys. Precious alloys must be heated slowly
and remain in the crucible to heat-soak whereas Chrome-Cobalt Alloys must be melted quickly to ensure
unchanged properties of the alloys and as soon as the complete fluidity has been reached they must be cast. We
recommend to turn heating power potentiometer on a value between 80-100.
♦ Place the flask and the crucible on the centrifugal arm. Put CCM in the crucible (min.quantity 15-20 grs, max.
quantity 100 grs) taking care to put the metal on the crucible bottom and against the crucible walls. Start
melting process turning heating power switch to the highest position. Once the melting process has started do
not open the cover otherwise the heating power will be interrupted. If necessary collect the metal on the
crucible bottom using the steel rod which will be introduced through the mesh of the machine cover. Operate
very quickly to prevent the steel from melting. When CCM has reached the complete fluidity it is ready to be
cast.
♦ Melting must be checked by eye or by the temperature controller using the blue screen placed under the
machine cover. Move the screen by rotating the black knob on the cover. DO NOT SET THE SET POINT.
♦ After casting, Chrome-Cobalt alloys leave a thin trace of metal on the side of the crucible which spontaneously
gets detached from the crucible and must be removed by means of a small tongs. If the trace of metal is thick
and does not come out of the crucible it indicates that the alloy was not completely molten. Do not remove it
from the crucible to avoid damaging it.
♦ After the first casting, check the crucible for cracks:
–
if it shows large cracks do not use it for another melt
–
if it shows small cracks it is a normal settling of material which will not bring any technical problem
♦ The crucible is working under severe conditions. It reaches the temperature of 1500°C in 30/60 seconds, it
then cools down during spinning and is then subjected to the next cycle. The contractions are detrimental to the
crucible.
♦ The crucible life will be longer if castings are made successively one after the other: overage life 15-20
castings. If castings are made in interrupted sequences i.e. with long interval between one and the following
melting, crucible will cool down continuously and its life will be shorter: average life 8-10 castings.
A100.425A100.481
MODULAR 6
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