In a Vacuum Metallurgy (Casting), a mold needs to be heated (500 to 700 degrees) to reduce thermal shock on the metal surface. Normally, a gas fired oven is employed for such job, but in a vacuum environment how do you achieve the same?
Ok, After Some Wandering on Google, I came to know the process,
One Idea is to heat mold by radiation, A ceramic heater could be suitable for it.
But the way it is actually done is,
First preheat the mold in a gas fired oven, and in parallel start vacuum induction furnace to melt the material in different chamber,
once mold and material is ready to be pour, put mold in a vacuum chamber for casting, close the chamber and starts molding.
this video gives nice explanation of the process.
A second idea for added control, if needed:
If your molders can accomplish it, you could also bury a heating coil in the mold before you harden it. The heating cable would need to be able to withstand the liquid metal temperatures, so something like tungsten would be required. This would also allow some control of the process after pouring - if you needed to get to a different metallurgical state, for example. The heater near the edges would keep the edges hot while the inside cools.