Vacuum Casting or not?


i’m Ivan from 'spain. can you help me, please? in this moment i
bought a induction overpressure machine, i cast palladium white gold
and i use special investment fot this porpuse. i melt the metal
cover with nitrogen and when it melts i reduced the temperature 30c,
(i melt at 1200c and i pour it at 1170c) i try with vacuum the
crucible chamber but in this moment i not vacuum in the crucible
chamber i only melt it with protective gas. What you recomend vacuum
the metal or not?. i always vacuum the flask and after this the
overpressure. my problem is that i have micro gas porosity i this
that is a reaction between the investment breakdown and the temper of
the metal. i take the flask at 482c.

please tell me something about this. what you recomend?. thanks for