Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B7/00—Heating by electric discharge
  • H05B7/005—Electrical diagrams
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/02—Details
  • H05B3/03—Electrodes

Definitions

• the present invention relates to a method for melting a solid material, in particular a metallic or ceramic charge, in an electric furnace, with the aim of forming an electrofused product, comprising at least two electrodes between the free ends of which an electric current can be created, for example in the form of an arc.
• One of the essential aims of the present invention is to propose a process allowing the manufacture, in a very simple and economically justified manner, of an electrofused product from very diverse solid materials electrically conductive or not.
• the charge of the solid material to be melted must preferably be electrically conductive. If the load is non-conductive, special precautions must be taken to start the fusion, such as the addition of carbon or graphite, to allow the creation of an electric current through the load.
• the invention aims to propose a method which makes it possible to remedy the drawbacks of known methods and which may also be suitable for an electrically conductive or non-conductive load without the latter, special precautions must be taken.
• said ends of the electrodes are brought into contact with said solid material to be melted, bringing them close enough to one another to be able to create between these electrodes a current electric, an electric arc is created between them so as to be able to melt the solid material located near the ends of the electrodes and the ends are then gradually moved apart from each other as the progress of the melting of the solid material, while maintaining them in contact with this material and ensuring the passage of electric current between the electrodes and through the molten part of the charge forming between them.
• the invention also relates to an electric furnace for the preparation of an electrofused product, in particular for the implementation of the above-mentioned process.
• This furnace is characterized by the fact that the electrodes are inclined with respect to each other and movable with respect to each other between a close position, where their free ends are possibly in contact with one another. other, and a spaced position, where these ends are at a certain distance from each other, means being provided to allow these ends to be moved in a substantially continuous manner between these two positions.
• the electrodes are each mounted on an electrically insulated support.
• the electrodes are mounted laterally in the crucible of the furnace so as to be able to undergo a translation between the two aforementioned positions.
• Figure 1 is a schematic view of a vertical section of an oven according to this particular embodiment.
• Figure 2 is a view along line II-II of Figure 1.
• FIG. 3 is a schematic representation of the electrode supply circuit.
• the same reference numbers relate to identical elements.
• the invention relates, in general, to a process for the melting of a solid material which can be of very varied nature, but which is more particularly formed by a charge of refractory products intended to be subjected to oxidation, in the purpose of forming an electrofused refractory product.
• the fusion takes place in an electric oven comprising at least two electrodes between the free ends of which can be created an electric current supplying the energy necessary for said fusion.
• the load to be melted is not electrically conductive or not very conductive, as is for example the case for solid ceramic materials
• the said ends of the electrodes are brought into contact with one another. other and with said solid matter to be melted.
• an electric arc is created between these electrodes so as to obtain the heating of the solid material located near the ends of the electrodes and thus be able to melt the latter.
• these ends are gradually moved apart from one another as the solid material progresses, while keeping these electrodes in contact with the solid material and ensuring that the electric current may remain between the electrodes and through the molten part of the charge forming between them.
• the heating is essentially due to the Joule effect of the resistance opposed by the load, in which the electrodes are partially immersed, to the passage of the electric current. It is, in fact, thus that a solid material which is not electrically conductive generally becomes electrically conductive when the latter is brought to the liquid state.
• the material to be melted is sufficiently electrically conductive and is, for example, formed of a metallic charge
• the heating obtained is thus due, in part to the heat of the arcs sprung up within the solid matter and, in part, to the Joule effect of the resistance opposed by the charge, in which the electrodes are partially immersed, in passing electric current.
• the close and apart positions may vary depending on the nature of the load to be melted.
• the electrodes practically touch or are very close to each other so as to be able to create an arc between their opposite ends, while this is not necessarily the case for a conductive load.
• a convection stirring is created in the latter before discharging it.
• This mixing is advantageously created by bringing together again the electrodes from each other for a while after all of the material is melted.
• the appended figures relate to an electric furnace for the manufacture of an electrofused product and in particular for the implementation of the method described above.
• This furnace comprises a crucible 1 closed at its upper part by a vault 2 in which an opening 3 is provided for introducing the charge to be melted into the crucible 1.
• Two electrodes 4 and 5, inclined with respect to each other, are each mounted on an electrically insulated support 6 and are located laterally with respect to the crucible 1, on either side of the latter, and this is in such a way as to be able to undergo a translation between a close position, where their free ends are possibly in contact with one another, and a separated position, where these ends are at a certain distance from each other .
• the electrodes freely penetrate into openings provided in the side walls 1 ′ of the crucible 1 and the cross section of which is such as to form an annular passage 19 allowing the entry of air into the furnace and the tilting of the electrodes.
• the angle ⁇ formed between the axes of the electrodes can vary between 15 ° and 165 °.
• the tilting advantageously takes place around a point 28 outside the oven and sufficiently spaced from the wall l 'of the latter, so as to obtain a rocking arm as large as possible of the electrodes 4 and 5 in the oven and thus a control perfect 1 evolution of the fusion regardless of the amount of material used.
• This tilting point 28 is located in practice on the support 6.
• each support 6 comprises a base 7 on which is fixed a column 8 to the upper end of which, forming the tilting point 28, is articulated a cradle 9 in which an electrode can be fixed in a removable manner by hoops 10.
• an adjustment flywheel 11 motorized or not is provided at cradle 9 making it possible to subject the electrodes to translation in the direction of the arrows 12 and thus to vary the spacing between the free ends 13 of the electrodes 4 and 5 inside the crucible 1. This spacing can also be adjusted by a tilting of the electrodes around point 28, as already indicated above.
• the bottom of the crucible 1 has a cylindrical outer wall 15 with which it rests, by means of rollers 16, on a base 14, these rollers being able to move in rails 17 provided on this cylindrical wall 15.
• a tap hole 18 is formed in the side wall of the crucible 1, substantially halfway up the latter.
• the electrodes are generally mounted in the walls of the latter and are suspended to tilt in relatively complex devices subjected to high temperatures for which, therefore, very important precautions must be taken, in particular for protection of the electrodes against these high temperatures.
• the presence of such devices is also often the reason why these known ovens can only work at temperatures of the order of 1600 ° C.
• FIG 3 which schematically shows the electrical supply circuit of the electrodes 4 and 5, is connected, at 29, to the network in a traditional way by means of a circuit breaker, not shown, and comprises a coil of self-induction 20 which can be connected in series with the electrodes 4 and 5 when the latter are in their above-mentioned close position.
• a switch 21 is provided for short-circuiting this coil 20 when the electrodes 4 and 5 are in their above-mentioned separated position.
• This circuit further comprises a transformer 27 for applying the voltage across the electrodes and ensuring the density of the current necessary to create the fusion. It can, more particularly, be a conventional transformer with fixed voltage ratio, e.g. 220V / 11000V. Finally, a main switch 22 makes it possible to close the electrical circuit and thus to energize the electrodes 4 and 5.
• the switch 22 is first closed, making sure that the switch 21 is in its open position and that the electrodes 4 and 5 are immersed by their free ends in the charge to melt or at least in contact with it, while in their close position.
• the electrodes 4 and 5 are advantageously brought closer to one another, preferably at a sufficiently large distance below the level of this molten material, and, if necessary, we open the switch
• a 1500 kg load was introduced into the oven which had the following composition: 33% zirconium oxide, 50% aluminum oxide, 14% silicon oxide and 3% alkali salt formed of bicarbonate sodium, while its average particle size varied from 0.5 mm to 15 cm (diameter).
• the free ends 13 of the two electrodes 4 and 5 were brought, which, for this particular case, were made of graphite, one near the other at the level of the solid mass previously introduced into the crucible 1 and the free ends 13 of the latter have been partially covered with a portion of the load, so that they are submerged.
• the energy at the electrodes was around 300k. After about 5 minutes, a quantity of the molten charge 24 was obtained around the ends 13 of the electrodes 4 and 5 sufficient to allow the self-induction coil 20 to be short-circuited and the switch 21 was therefore closed in at the same time gradually moving the electrodes away from each other.
• This liquid mass 24 being electrically conductive, the electric current therefore propagated between these electrodes 4 and 5 through the molten part 24 of the charge.
• the total duration of the fusion was around 45 minutes, while the temperature was around 2250 ° C. The heat thus produced was sufficient to allow the charge to gradually melt while the distance between the electrodes was continued to increase, until the complete charge was melted.
• Other types of fillers have been treated in this oven in a similar manner.
• this melting was carried out continuously by maintaining the crucible 1 in an inclined position in such a way that the molten vitreous mass could flow by overflowing through the tap hole 18 as the progression of melting while at the same time adding the charge to melt in the crucible through opening 3 in the roof of the furnace.
• the oven can work both in direct current as in single-phase current as in three-phase current.
• the mounting of the electrodes 4 and 5 relative to the crucible 1 is such that it is possible to adjust their angle of incidence ⁇ relative to the level of the charge to be melted. In this way, it is ensured that the electrodes can also undergo a certain tilting on the column 8 of the support 6 with a relatively large amplitude, especially thanks to the fact that the tilting point is distant from the wall of the furnace.
• the load to be melted not only its composition can be very variable, but also its particle size. It can in particular be both powder and blocks having diameters of several tens of centimeters.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Furnace Details (AREA)
• Vertical, Hearth, Or Arc Furnaces (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
• Continuous Casting (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Glass Melting And Manufacturing (AREA)

Priority Applications (8)

Applications Claiming Priority (2)

Publications (1)

Family

ID=3888220

Family Applications (1)

Country Status (14)

Cited By (1)

Citations (4)

• 1994
  • 1994-06-24 BE BE9400604A patent/BE1008485A3/fr not_active IP Right Cessation
• 1995
  • 1995-06-19 EP EP95922361A patent/EP0768017B1/fr not_active Expired - Lifetime
  • 1995-06-19 AU AU27087/95A patent/AU705587B2/en not_active Ceased
  • 1995-06-19 SK SK1654-96A patent/SK283103B6/sk not_active IP Right Cessation
  • 1995-06-19 DE DE69504350T patent/DE69504350T2/de not_active Expired - Fee Related
  • 1995-06-19 CZ CZ19963760A patent/CZ289969B6/cs not_active IP Right Cessation
  • 1995-06-19 WO PCT/BE1995/000057 patent/WO1996000489A1/fr active IP Right Grant
  • 1995-06-19 CA CA002192068A patent/CA2192068A1/fr not_active Abandoned
  • 1995-06-19 AT AT95922361T patent/ATE170356T1/de not_active IP Right Cessation
  • 1995-06-19 RU RU97101116A patent/RU2144285C1/ru not_active IP Right Cessation
  • 1995-06-19 PL PL95317937A patent/PL176908B1/pl not_active IP Right Cessation
  • 1995-06-19 ES ES95922361T patent/ES2124557T3/es not_active Expired - Lifetime
  • 1995-06-19 HU HU9603424A patent/HU220470B1/hu not_active IP Right Cessation
• 1996
  • 1996-12-20 BG BG101072A patent/BG62150B1/bg unknown

Patent Citations (4)

Non-Patent Citations (1)

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