Abstract: The present invention relates to a multistage vertical graphitization furnace system including a feed part including a silo where raw materials are stored, a low-temperature treatment part having a low-temperature heat treatment furnace which receives the raw materials from the feed part, and heats the raw materials to remove impurities, a high-temperature treatment part having a high-temperature heat treatment furnace to produce synthetic graphite, a cooling part for water-cooling the synthetic graphite produced in the high-temperature treatment part, and a discharge part for taking out the synthetic graphite discharged from the cooling part.

Abstract: An induction heating tool that holds voltage or current supplied to the induction tank circuit constant and tracks changes in the other of voltage or current during each induction heating cycle. The disclosed induction heating tool exploits the fact that the resistance an attachment plate increases along with the temperature of the attachment plate. During an induction heating cycle, the attachment plate is magnetically coupled to a work coil and the resistance of the attachment plate is reflected to the circuit. Changes in the resistance of the attachment plate alter the pattern of energy delivery from the work coil to the attachment plate in a predictable way. Calculations accurately predict the temperature of the attachment plate over a wide variety of ambient conditions, including the presence of moisture at the membrane/attachment plate interface. The disclosed induction heating tool produces consistent results without calibration for ambient conditions.

Abstract: A channel type induction furnace with a furnace floor that is inclined downwards from an operative rear of the furnace hearth towards an opposing operative front of the hearth, with a wall at the front comprising a bottom section and a top section, with the bottom section extending further into the hearth than the top section, and the bottom section terminating in an upper edge in abutment with the top section, with a down-passage to an induction heater, located proximate the front wall, having an inlet in the floor at a location proximate the base of the front wall and up passage(s) having an outlet in the floor at a location in abutment with the base of the bottom section and with the bottom section being provided with a vertical slot extending upwards above the or each up-passage through it and opening onto the upper edge of the bottom section.

Abstract: A method is provided for joining a filler material to a substrate material. The method includes melting the filler material within a melting chamber of a crucible such that the filler material is molten. The crucible has an outlet fluidly connected to the melting chamber. The method also includes holding the filler material within the melting chamber of the crucible by applying a first pressure differential across the outlet of the crucible, and releasing the filler material from the melting chamber of the crucible by applying a second pressure differential across the outlet of the crucible to deliver the filler material to a target site of the substrate material. The second pressure differential has a different value than the first pressure differential.

Abstract: An induction furnace comprising a upper furnace vessel; an induction coil positioned below the upper furnace vessel; and a melt-containing vessel positioned inside the induction coil and communicably connected to the upper furnace vessel, wherein the positioning of the melt-containing vessel inside the induction coil defines a gap between an outside surface of the melt-containing vessel and an inside surface of the induction coil. A system for direct-chill casting comprising at least one an induction furnace; at least one in-line filter operable to remove impurities in molten metal; at least one gas source coupled to a feed port associated with the gas; and at least one device for solidifying metal by casting. A method of cooling an induction furnace comprising introducing a gas into a gap between an induction coil and a melt-containing vessel positioned inside the induction coil; and circulating the gas through the gap.

Abstract: A tapping device and method using induction heat for melt comprises melting furnace made of steel; heating unit disposed in the upper part in the melting furnace and made of graphite material; induction coil wound around the heating unit; insulator disposed adjacent to the bottom surface of the lower part of the melting furnace; supporter disposed outside the insulator; and firebricks disposed on the bottom surface of melting furnace and outside the supporter.

Abstract: Disclosed are embodiments of a vessel configured to contain a secondary magnetic induction field therein for melting materials, and methods of use thereof. The vessel can be used in an injection molding apparatus having an induction coil positioned along a horizontal axis and adjacent to the vessel. The vessel can have a tubular body configured to substantially surround and receive a plunger tip. At least one longitudinal slot extends through the thickness of the body to allow and/or direct eddy currents into the vessel during application of an RF induction field from the coil. The body also includes temperature regulating lines configured to flow a liquid within. The temperature regulating lines can be provided to run longitudinally within the wall(s) of the body between its inner bore and outer surface(s). A flange may be provided at one end of the body to secure the body within an injection molding apparatus.

Abstract: An integrated process control installation is provided for electric induction metal melting furnaces with variable furnace states. The integrated process control installation can include supporting charge delivery and slag removal installations, and furnace process operations for process control of melting metal in the furnaces. The variable furnace states, supporting installations, and furnace process operations are controlled by a supporting processing installation, while a robotic apparatus performs the furnace process operations.

Abstract: An induction melting furnace having an asymmetrical sloping bottom. The melting furnace includes: an induction coil member provided on the melting furnace so as to melt waste contained in the furnace by vitrification; a bottom unit provided in a lower part of the melting furnace, the bottom unit asymmetrically sloping downward in a direction toward a glass discharge port that is formed through the bottom unit; and a cooling member integrated with the bottom unit. Due to the asymmetrical sloping bottom of the furnace, waste in the furnace can be completely melted and can be easily discharged to the outside and, accordingly, the time and cost required to treat the waste are reduced and this improves work efficiency when treating the waste. Further, due to the insulation material, the melting furnace can be protected from electric damage that may be caused by electric arc.

Abstract: Apparatus and method are provided for electric induction heating and melting of a transition material that is non-electrically conductive in the solid state and electrically conductive in the non-solid state in an electric induction heating and melting process wherein solid or semi-solid charge is periodically added to a heel of molten transition material initially placed in a refractory crucible. Induction power is sequentially supplied to a plurality of coils surrounding the exterior height of the crucible at high power level and high frequency with in-phase voltage until a crucible batch of transition material is in the crucible when the induction power is reduced in power level and frequency with voltage phase shifting to the induction coils along the height of the crucible to induce a unidirectional electromagnetic stir of the crucible batch of material.

Abstract: The invention comprises a double loop channel type induction furnace of which the floor has a base on a first side of its hearth and a ramp which rises from the base to terminate in a plateau above the passages at a location distal from the first side. The ramp and plateau extends at least partly between opposing end walls of the furnace, and the plateau includes a trench which extends at least partly between opposing ends of the plateau. The trench is in fluid communication with the passages and the bottom of the trench is located in a plane higher than the plane in which the furnace floor is located. The base of the furnace floor is in fluid communication with the central passage by means of a floor passage that extends from the base of the floor to the central passage through the ramp below the trench.

Abstract: Disclosed herein is a melting apparatus for melt-decontaminating radioactive metal waste. The melting apparatus includes a melting furnace, a high frequency generator, a ladle, a bogie, a cooling unit and a dust collector. The melting furnace includes a crucible into which the metal waste is input, and an induction coil which is wound around the crucible to melt the metal waste. The induction coil has a hollow hole in which cooling fluid flows. The high frequency generator applies high-frequency current to the induction coil. The ladle supplies molten metal, from which slag has been removed in the crucible, into molds. The bogie is disposed adjacent to the ladle and is provided with the molds, each of which forms an ingot using the molten metal supplied thereinto. The cooling unit cools the cooling fluid and circulates it along the induction coil. The dust collector filters out dust and purifies gas.

Abstract: An induction furnace includes a melting induction coil for inductively heating a pair of susceptors for melting particulate material falling freely in a free fall zone between the susceptors. A feeder having a rotatable hollow shaft with fingers extending therefrom breaks up the material, which falls onto a vibrating dispersion plate and then into the free fall zone. A preheating induction coil inductively heats a susceptor which radiates heat to particulate material moving over the dispersion plate. An adjustable gap between the feeder and dispersion plate controls material flow. A funnel collects falling molten material and directs it through a nozzle into a mold. Induction coils control melting within the funnel. One induction coil heats the nozzle and may be controlled to allow the nozzle to cool sufficiently to form a solid plug in the nozzle whereby molten material pools above the plug.

Abstract: An induction melting furnace having an asymmetrical sloping bottom. The melting furnace includes: an induction coil member provided on the melting furnace so as to melt waste contained in the furnace by vitrification; a bottom unit provided in a lower part of the melting furnace, the bottom unit asymmetrically sloping downward in a direction toward a glass discharge port that is formed through the bottom unit; and a cooling member integrated with the bottom unit. Due to the asymmetrical sloping bottom of the furnace, waste in the furnace can be completely melted and can be easily discharged to the outside and, accordingly, the time and cost required to treat the waste are reduced and this improves work efficiency when treating the waste. Further, due to the insulation material, the melting furnace can be protected from electric damage that may be caused by electric arc.

Abstract: A cold crucible induction melter includes an induction coil and a melting furnace. The induction coil serves as a water cooled segment to directly transmit an induced current to a molten material in the cold crucible induction melter (CCIM), improving energy efficiency. Simultaneously, the structure of the CCIM is simplified and enables a smooth discharge even when the molten material consists of a ceramic or a metal material with a high melting point. The cold crucible induction melter heats and melts waste using an induced current which is generated in a water cooled segment by a high frequency current that is applied to the induction coil. The water cooled segment and the induction coil are disposed in a vertical direction so that the induced current that is generated by the induction coil is directly transmitted to the molten material.

Abstract: Apparatus and method are provided for heating and melting of materials by electric induction heating of susceptor components in a crucible of the furnace. The susceptor components comprise at least an array of susceptor rods arranged around the inner perimeter of the crucible. A susceptor base may also be provided in the crucible with connection to one end of the susceptor rods. One or more susceptor tubes may also be used within the interior volume of the crucible. Alternating current flow through one or more induction coils surrounding the exterior of the crucible generate magnetic flux fields that couple with the susceptor components to inductively heat the susceptor components. Heat from the susceptor components transfers to the material in the crucible to heat and melt the material.

Abstract: The introduction of spray formed metals into critical applications in the aircraft engine and power generation industries has been hampered by the possibility of erosion of oxide particles from a crucible lining or pouring nozzle in conventional spray forming equipment. These oxide particles may become inclusions that limit low-cycle fatigue life of parts. Use of a cold-walled induction guide (CIG) with an electrical insulation layer between copper CIG elements and the liquid metal offers a means of delivering ceramic-free alloys to a spray system with improved efficiency. CIG design options facilitated by a new oven-brazed fabrication technique resolve induction coil environmental isolation issues, correct thermal strain tolerance problems, facilitate dual frequency induction designs, allow improved electrical coupling efficiency and thermal efficiency, result in improved melt flow initiation, and facilitate disassembly without damage from the solidified melt.

Abstract: The invention relates to a method and device for supersonically injecting oxygen into a furnace, in particular a cupola furnace, in which the total oxygen required for the furnace operation is injected with the aid of two distinct circuits, i.e., the first circuit comprising at least one supersonic oxygen injecting nozzle and a second circuit which comprises additionally oxygen injecting means and is connected to the first circuit by pressure-sensitive means, such as a discharging device (or upstream pressure adjuster), in such a way that a stable pressure is obtained in the first circuit upon the attainment of the maximum flowrate thereof, wherein the first circuit can consists of several supersonic nozzle groups.

Abstract: The present invention relates to an apparatus and a method for manufacturing a thermoelectric conversion element. The present invention provides an apparatus for manufacturing a thermoelectric conversion element that can easily realize a high-density array of thermoelectric conversion elements and secure connection reliability. This is an apparatus for manufacturing a thermoelectric conversion element that sucks a p-type or n-type thermoelectric conversion material into heat-resisting insulating tube 102 and includes preheating apparatus 205 that can heat tube 102 to a predetermined temperature before sucking the melted thermoelectric conversion element. Tube 102 whose temperature condition is adjusted by being heated by preheating apparatus 205 is inserted into crucible 204 and the molten thermoelectric conversion material is sucked into tube 102 by decompression apparatus 201.

Abstract: An open bottom electric induction cold crucible with a slotted wall extending below one or more induction coils surrounding the partial exterior height of the crucible is used in an electromagnetic casting process for the production of ingots. A bottom magnetic shield is provided around the outer perimeter of the crucible's slotted wall in the vicinity of the bottom opening and the bottom termination of the wall slots and the bottom connecting member.

Abstract: An electric induction gas-sealed tunnel furnace and process are provided. The exterior of the furnace's enclosure that forms a closed tunnel region is surrounded at least along its longitudinal length by a gas-tight barrier chamber that can be filled with a barrier gas to a different pressure than the pressure of the process gas in the closed tunnel region of the furnace. The inductors used to induction heat strips or plates in the closed tunnel region can be positioned within or outside of the gas-tight barrier chamber around the longitudinal length of the closed tunnel region.

Abstract: A method for the continuous production of products from a melt is provided. The method includes heating the melt to a predetermined temperature in a skull crucible, the bottom of which is formed from electrically non-conductive, but thermally conductive material.

Abstract: An induction heated furnace assembly for producing a directionally solidified casting includes a susceptor that tailors strength of the magnetic field within the chamber to provide a desired grain structure in a completed cast part. The susceptor proportionally blocks portions of the magnetic field to provide different levels of magnetic stirring within the molten material at different locations within the furnace assembly stirring induced by the magnetic field is controlled and varied throughout the furnace assembly to create the desired grain structures in the completed cast article.

Abstract: A cold crucible induction furnace has a slotted-wall with a slotted inner annular protrusion that is disposed around the base of the crucible's melting chamber. The protrusions may be separated from the base by a gap that can be filled with an electrical insulating material. Slots may also be provided in the protrusions and/or the outer perimeter of the base.

Abstract: A stacked induction furnace system includes a first furnace having an induction coil to heat and melt a substantially non-conductive material contained in an upper crucible. The upper crucible contains an opening in a bottom surface thereof to drain molten material therefrom. A second furnace is positioned below the first furnace and includes a lower crucible to receive the molten material drained from the opening and is arranged to maintain the molten state of the material in the lower crucible. One or more power sources are provided to power the first furnace and the second furnace.

Abstract: Apparatus and methods of operation are provided for a cold-crucible-induction melter for vitrifying waste wherein a single induction power supply may be used to effect a selected thermal distribution by independently energizing at least two inductors. Also, a bottom drain assembly may be heated by an inductor and may include an electrically resistive heater. The bottom drain assembly may be cooled to solidify molten material passing therethrough to prevent discharge of molten material therefrom. Configurations are provided wherein the induction flux skin depth substantially corresponds with the central longitudinal axis of the crucible. Further, the drain tube may be positioned within the induction flux skin depth in relation to material within the crucible or may be substantially aligned with a direction of flow of molten material within the crucible. An improved head design including four shells forming thermal radiation shields and at least two gas-cooled plenums is also disclosed.

Abstract: Apparatus for producing a semi-solid metal alloy from a molten charge includes vertically aligned treatment zones which are provided by vertically aligned passages defined by a plurality of spirally wound flow pipes which are interspersed between spirally wound induction coils. A container is mounted on a charging arrangement which displaces a first charge upwardly into the first treatment zone. Successive charges are introduced in a similar fashion thereby urging the previously introduced charge upwardly along the train of zones and until the leading charge is ejected from the top of the apparatus. The charge in each zone is subjected to controlled cooling and an induced electromagnetic field. The strength of the field and the rate of cooling are controlled to impede dendritic crystallisation and to promote globular primary crystal formation.

Abstract: A molten material can be heated, melted and directly solidified in a single vessel. Induction heating and melting of the molten material is achieved by magnetically coupling the field produced by current flow in a plurality of induction coils surrounding the vessel with either the molten material in the vessel, or a susceptor surrounding molten material in the vessel. Current flow is selectively removed from the plurality of induction coils, and a cooling medium surrounding the vessel, such as water flowing through hollow induction coils, solidifies the molten metal into a highly purified crystalline solid.

Abstract: Apparatus and methods of operation are provided for a cold-crucible-induction melter for vitrifying waste wherein a single induction power supply may be used to effect a selected thermal distribution by independently energizing at least two inductors. Also, a bottom drain assembly may be heated by an inductor and may include an electrically resistive heater. The bottom drain assembly may be cooled to solidify molten material passing therethrough to prevent discharge of molten material therefrom. Configurations are provided wherein the induction flux skin depth substantially corresponds with the central longitudinal axis of the crucible. Further, the drain tube may be positioned within the induction flux skin depth in relation to material within the crucible or may be substantially aligned with a direction of flow of molten material within the crucible. An improved head design including four shells forming thermal radiation shields and at least two gas-cooled plenums is also disclosed.

Abstract: A method of operating an induction furnace so as to receive electric arc furnace (EAF) dust, basic oxygen furnace (BOF) sludge/dust and/or other iron and volatile metals containing materials as a feed stream on a batch, continuous or semi-continuous basis together with a iron-containing material feed, and therefrom produce an iron-containing hot metal or pig iron product while recovering iron value from the feed materials and recovering volatile metal components contained in the feed materials.

Abstract: An induction melting furnace comprises a melt chamber for heating a melt either directly by magnetic induction, or indirectly by magnetic induction heating of the melt chamber, or a combination of the two, and a meter chamber connected to the melt chamber for providing a metered discharge of the melt from the furnace. A gas can be injected into the furnace to provide a blanket over the surface of the melt in the melt chamber and a pressurized flush of the metered discharge of the melt from the meter chamber.

Abstract: An induction melting furnace comprises a melt chamber for heating a melt either directly by magnetic induction, or indirectly by magnetic induction heating of the melt chamber, or a combination of the two, and a meter chamber connected to the melt chamber for providing a metered discharge of the melt from the furnace. A gas can be injected into the furnace to provide a blanket over the surface of the melt in the melt chamber and a pressurized flush of the metered discharge of the melt from the meter chamber.

Abstract: In a metallurgical vessel (1) having a tapping apparatus (5) for the slag-free withdrawal of liquid metal (3) from a molten metal bath (3) which is disposed in the vessel (1), a first leg (11) of a discharge duct (10) passes through the refractory vessel wall (15) and an overflow edge (14) in the connecting region of the two legs (11, 12) of the discharge duct (10) is higher than the upper edge (18) of the inlet opening (17) of the discharge duct. The molten metal (3) in the discharge duct is preferably inductively heatable.

Abstract: The vacuum induction melting system is designed to be operated in a continuous or semi-continuous manner for extended periods of time for increased efficiency, and makes it possible to easily and quickly remove the induction furnace from the melt chamber when it becomes necessary to replace and rebuild the furnace. The melting system includes a melt chamber which forms an airtight enclosure, with an induction furnace located within the melt chamber. A charging chamber is communicatively connected to the melt chamber adjacent its upper end. The charging chamber includes a door providing access to the interior of the charging chamber so that a charge of raw materials can be placed therein. An isolation valve is located between the melt chamber and the charging chamber and is movable between open and closed positions.

Abstract: An induction melting furnace comprises a melt chamber for heating a melt either directly by magnetic induction, or indirectly by magnetic induction heating of the melt chamber, or a combination of the two, and a meter chamber connected to the melt chamber for providing a metered discharge of the melt from the furnace. A gas can be injected into the furnace to provide a blanket over the surface of the melt in the melt chamber and a pressurized flush of the metered discharge of the melt from the meter chamber.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: A melt guide includes a base plate having internal cooling channels and a center aperture extending vertically therethrough. A unitary drain bushing is removably mounted in the aperture and is readily replaceable after wear thereof.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: A metallothermy method includes continuously withdrawing an ingot of a metal product such as uranium or a uranium alloy as it is formed from an oxide or salt of the metal. The method employs upper and lower communicating crucibles. The upper crucible contains a layer of reducing medium floating on a solvent medium. The metal oxide or metal salt is reduced as it is introduced into the layer reducing medium to form metal particles and slag. The settling metal is melted by further induction heating, collected in the lower crucible and withdrawn. The slag is absorbed by the solvent medium which is regenerated with the use of electrolysis.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: A vacuum induction melting system includes a melt chamber which forms an airtight enclosure, with an induction furnace located within the melt chamber. A mold tunnel is connected to the melt chamber adjacent its lower end, with the mold tunnel including a pour opening which communicates with the melt chamber and through which molten metal poured from the furnace can enter the mold tunnel. A mold carriage is positioned within the mold tunnel for receiving and carrying one or more molds adapted for receiving molten metal. An isolation valve is located between the melt chamber and the mold tunnel for isolating the mold tunnel from the melt chamber to allow for removing the mold carriage from the mold tunnel for loading or unloading of molds thereon. A mold transport assembly is provided for moving the mold carriage from a pouring position within the mold tunnel to a loading position located outside of the mold tunnel.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: An induction heating furnace includes a furnace body having a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other, a first induction heating coil arranged at an outer periphery of the side wall for subjecting a to-be-heated material accommodated in the furnace body to induction heating and a melt-use power source for supplying AC power to the first induction heating coil.

Abstract: An assembly includes a tapping device for flow therethrough of molten material and a cooled inductor to be connected to an electrical source and mounted with respect to the tapping device to be inductively coupled to one of the tapping device and the molten material flowing therethrough. The inductor includes an electrically conductive induction coil having therethrough at least one cooling passage. Each cooling passage has connected thereto at least one supply line for supply thereto of cooling fluid and at least one discharge line for discharge therefrom of the cooling fluids.

Abstract: An apparatus and a method for melting solid metals, including iron, are provided. The apparatus includes a vertical shaft furnace through which the metal is fed. The shaft furnace is mounted on a horizontal induction furnace containing a molten pool of metal. Metal solids are charged at the top of the vertical shaft furnace down onto a refractory pedestal in the molten metal pool or suspended magnetically in the vertical shaft above gas burners. The metal is melted by contact with the molten metal pool. The combination of oxygen fuel burner preheating and induction melting creates an extremely efficient melting unit that can process metal at a much lower cost than conventional systems while preventing the oxidation problems incurred by apparatuses which melt metal using combustion only.

Abstract: A guide tube structure for flux concentration is provided. The discharge guide tube comprises a central orifice that extends from a source of metal to an outlet in the discharge guide tube for directing a stream of melt therethrough; a structure that generates an electromagnetic field in the discharge guide tube; and an interior discharge guide tube flux concentration configuration that is capable of concentrating at least one of heat, electromagnetic field, and electromagnetic flux onto the stream of melt that flows through the central orifice. The electromagnetic field is applied at a substantially constant level.

Abstract: A melting furnace for insulating materials is provided with a cooled crucible (10) having continuous metal side malls, a partitioned and cooled bottom (12) and at least one induction coil (28) placed under the bottom which serves as the sole heating means. The depth of the melting bath contained in the crucible and the excitation frequency of the induction coil are selected so that the depth and half of the inside radius of the crucible are less than the skin thickness of the bath.