Patent ID: 7011136

Claim:
A furnace apparatus for melting metal comprising: a microwave chamber; at least one tuned microwave generator and a power supply for generating microwave energy within the microwave chamber; a one-piece crucible disposed in the microwave chamber and formed from a composition of material that is configured and composed to hold both solid and molten metal and that is refractory to a molten metal and that includes susceptors of microwaves, said one-piece crucible comprising a single stratum that partially absorbs and partially transmits the microwave energy; metal disposed in the one-piece crucible, the metal being disposed for (1) absorbing heat from the one-piece crucible when the metal is in a solid state and is not coupled to the microwave energy and (2) absorbing heat from the one-piece crucible and absorbing energy from the microwaves to produce heat when the metal is heated by the one-piece crucible to a temperature at which the metal will couple to the microwave energy; a thermal insulation casket enclosing the one-piece crucible, where the casket is formed from a material that does not couple substantially with microwave energy; and the one-piece crucible being composed and configured to absorb microwaves, generate heat due to the absorption of microwaves, and transfer heat to the metal at least until the one-piece crucible temperature approaches the melting temperature of the metal, the one-piece crucible being further composed to transmit microwaves through the one-piece crucible such that some of the microwave energy couples with the metal when the metal approaches its melting temperature and accelerates the rate of temperature increase of the metal to thereby melt the metal within the one-piece crucible.