The invention relates to a levitation melting process and an apparatus for producing castings comprising a ring-shaped element of a conductive material for introducing the casting of a molten batch into a casting mould. In the process, the ring-shaped element is introduced into the region of the alternating electromagnetic field between the induction coils in order to cast the molten batch, thereby initiating a targeted run-off of the melt into the casting mould by influencing the induced magnetic field.

A method of cooling an electric induction furnace for melting and holding a reactive metal or alloy is provided where the electric induction furnace has an upper furnace vessel and an induction coil in a modular inductor furnace is positioned below the upper furnace vessel with a melt-containing vessel positioned inside the induction coil with a gap between the outside surface of the melt-containing vessel and the inside surface of the induction coil that is used to circulate a cooling fluid for cooling the melt-containing vessel to inhibit leakage of the reactive metal or alloy melt from the melt-containing vessel. The melt-containing vessel can be integrated with a cooling system for cooling the melt-containing vessel. Modularity of the melt-containing vessel, induction coil and cooling system facilitates servicing of the modular inductor furnace without disassembly of the entire electric induction furnace.

A method of cooling an electric induction furnace for melting and holding a reactive metal or alloy is provided where the electric induction furnace has an upper furnace vessel and an induction coil in a modular inductor furnace is positioned below the upper furnace vessel with a melt-containing vessel positioned inside the induction coil with a gap between the outside surface of the melt-containing vessel and the inside surface of the induction coil that is used to circulate a cooling fluid for cooling the melt-containing vessel to inhibit leakage of the reactive metal or alloy melt from the melt-containing vessel. The melt-containing vessel can be integrated with a cooling system for cooling the melt-containing vessel. Modularity of the melt-containing vessel, induction coil and cooling system facilitates servicing of the modular inductor furnace without disassembly of the entire electric induction furnace.

A feedthrough assembly may include a feedthrough conductor, a first insulator, and a first metal gasket forming a seal between the feedthrough conductor and the first insulator. The feedthrough assembly may additionally include a body, and a second metal gasket forming a seal between the body and the first insulator. Methods of manufacturing such feedthrough assemblies may include compressing the first metal gasket between the feedthrough conductor and the first metal gasket to form a seal therebetween. The methods may further include compressing the second metal gasket between the body and the first insulator to form a seal therebetween. Induction furnace systems may include one or more such feed assemblies.

A feedthrough assembly may include a feedthrough conductor, a first insulator, and a first metal gasket forming a seal between the feedthrough conductor and the first insulator. The feedthrough assembly may additionally include a body, and a second metal gasket forming a seal between the body and the first insulator. Methods of manufacturing such feedthrough assemblies may include compressing the first metal gasket between the feedthrough conductor and the first metal gasket to form a seal therebetween. The methods may further include compressing the second metal gasket between the body and the first insulator to form a seal therebetween. Induction furnace systems may include one or more such feed assemblies.

A silicon wafer is provided in which a dopant is phosphorus, resistivity is 1.2 mΩ.Math.cm or less, and carbon concentration is 3.5×10.sup.15 atoms/cm.sup.3 or more. The carbon concentration is decreased by 10% or more near a surface of the silicon wafer compared with a center-depth of the silicon wafer.

A silicon wafer is provided in which a dopant is phosphorus, resistivity is 1.2 mΩ.Math.cm or less, and carbon concentration is 3.5×10.sup.15 atoms/cm.sup.3 or more. The carbon concentration is decreased by 10% or more near a surface of the silicon wafer compared with a center-depth of the silicon wafer.

An electric induction furnace for melting and holding a reactive metal or alloy is provided with an upper furnace vessel, an induction coil positioned below the upper furnace vessel, and a melt-containing vessel positioned inside the induction coil with a gap between the outside surface of the melt-containing vessel and the inside surface of the induction coil that can be used to circulate a cooling fluid for cooling the wall of the melt-containing vessel to inhibit leakage of the reactive metal or alloy melt from the vessel. The melt-containing vessel can be integrated with a cooling system for cooling the melt-containing vessel. The melt-containing vessel, induction coil and cooling system can be provided as modular components to facilitate servicing of the melt-containing vessel, the induction coil and the cooling system.

An electric induction furnace for melting and holding a reactive metal or alloy is provided with an upper furnace vessel, an induction coil positioned below the upper furnace vessel, and a melt-containing vessel positioned inside the induction coil with a gap between the outside surface of the melt-containing vessel and the inside surface of the induction coil that can be used to circulate a cooling fluid for cooling the wall of the melt-containing vessel to inhibit leakage of the reactive metal or alloy melt from the vessel. The melt-containing vessel can be integrated with a cooling system for cooling the melt-containing vessel. The melt-containing vessel, induction coil and cooling system can be provided as modular components to facilitate servicing of the melt-containing vessel, the induction coil and the cooling system.

The invention relates to a levitation melting process and a device for producing castings with movable induction units. In this process, induction units are used in which the opposite ferrite poles with the induction coils are movable and move in opposite directions. In this way, the induction units for melting the batches can be arranged close together in order to increase the efficiency of the induced magnetic field. When casting the molten batch, the induced magnetic field is reduced by increasing the distance between the ferrite poles with the induction coils, thus preventing the melt from touching the ferrite poles or the induction coils.