Furnace for direct induction melting of dielectric substances - esp. glass or vitreous enamel, where solid periphery of substance functions as crucible surrounded by induction coils

摘要

The substances are insulators when cold, but becomes conducting when near their m.pt. The furnace has a wall formed by one or more coaxial, helical induction coils with a vertical axis. The coils are made from tubes through which a coolant flows, so the coils form a cooler as well as an induction heater. The coils cool the periphery (P) of a charge (C) in the furnace, so the solid charge (C) forms a crucible contg. the molten part of the charge. The turns of the induction coils are pref. located close together so their cooling action keeps the periphery (P) of the charge (C) in a solid state. A graphite susceptor is pref. used to start melting. Used e.g. to melt 0.3-0.5 tonnes of glass or inorganic vitreous enamel using a medium frequency below 50 kHz, i.e. to obtain deep penetration.