Furnace installation for liquid metal, with electric heating and improved stirring

Abstract

Furnace installation for non-ferrous metals, comprising at least one chamber capable of containing liquid metal, and - at least two zones for liquid metal which are in fluid connection, as well as - heating means which are exclusively electrical and which comprise at least one immersion heater for heating the liquid metal and optionally at least one radiant heat source for preheating the furnace, - magnetic means for stirring the liquid metal, comprising at least one rotary permanent magnet, said magnetic stirring means being arranged in the chamber and / or below the chamber and / or on the side of the chamber.

Description

[0001] Installation of a furnace for liquid metal, with electric heating and improved stirring.

[0002] Technical field of the invention

[0003] The present invention relates to the field of non-ferrous metal casting, and more particularly to foundry equipment used in molding or recycling, which allows for the melting, homogenization, holding in molten form, and / or processing (i.e., most often, degassing, decanting, or filtering) of relatively small quantities of metal, with a molten metal capacity ranging from approximately 1 ton to approximately 10 tons, or even 15 tons. This equipment is significantly smaller than that used for the semi-continuous casting of rolling slabs or extrusion billets, which can reach a capacity of 100 tons, or even 130 or 150 tons.

[0004] Within the technical field thus delimited, the present invention relates to electric ovens.

[0005] State of the art

[0006] There is a strong trend towards decarbonizing industrial processes, in addition to the more general desire to save energy. For many processes, decarbonization requires replacing gas heating with electric heating. In non-ferrous metal foundries, melting and holding furnaces are usually gas-fired, although electric furnaces, particularly induction furnaces, are known. In the aluminum foundry sector, a fairly clear distinction exists between, on the one hand, furnace technologies for foundries attached to an electrolysis plant or a large semi-finished product plant, which generally produce large quantities of rolling plates and / or extrusion billets, or (especially for foundries attached to electrolysis plants) ingots or bars for remelting, and, on the other hand, furnace technologies for mold shops, which generally use smaller quantities of metal.There are also recycling melting furnaces which are generally relatively small in size.

[0007] In these furnaces, melting, which requires a very significant input of thermal energy, is often carried out using gas burners. Temperature maintenance can be achieved with electric immersion heaters; this also depends on the size of the furnace. Electric immersion heaters, on the other hand, are preferred in processing and filtration ladles, whose liquid metal capacity typically does not exceed one or two tons, as well as in chutes for transporting liquid metal by flow. A distinction is usually made between melting furnaces, in which solid metal is melted, and holding furnaces, in which the liquid metal (also called the "bath") is held in a liquid state until it is used. The transition from one to the other occurs through a chute, or at least, for a given furnace, a distinction is made between the melting phase and the holding phase.In the first case, the melting furnace is capable of delivering liquid metal to the holding furnace at the same time as solid metal is being introduced into the melting furnace for melting. In the second case, since the holding phase follows the melting phase, this is not possible: such a furnace necessarily operates in batch mode.

[0008] In the foundry industry, replacing gas heating systems with electric heating systems often results in energy savings for smelting, which is expressed in kWh per ton of metal. Among electric heating systems, immersion heaters are the most efficient because they direct the supplied electrical energy directly and solely onto the material to be kept molten. They also have the advantage, particularly compared to induction furnaces and radiant electric heating systems, of minimizing loss on ignition, that is, the fraction of metal lost in oxidized dross. This is why they are used in small holding furnaces and in ladles for processing molten metal.

[0009] Induction furnaces typically have a lower capacity than gas furnaces, ranging from approximately 2 to 30 tons. They cannot be used continuously, meaning they operate in batch mode and therefore cannot melt solid metal and remove liquid metal simultaneously.

[0010] In all these furnaces, the question of stirring the molten metal arises. Stirring is necessary to homogenize the temperature and chemical composition of the bath and to prevent the settling of intermetallic phases. During the metal melting process, stirring also improves heat exchange between the solid metal and the bath, shortening the melting phase, which reduces heat loss and loss on ignition. In large furnaces, stirring is done mechanically, for example, by a motorized device carrying a steel stirring tool on a long rod, which is immersed in the bath; to stir the molten metal, the device moves back and forth. In smaller furnaces, mechanical systems equipped with bladed rotors can be used. These mechanical systems are subject to significant wear, at least on the stirring tools, which incurs a cost.

[0011] Electromagnetic devices are also known for setting a non-ferrous metal bath in motion. These electromagnetic devices operate without moving mechanical parts. EP 2 206 998 and EP 2 381 201 (ZMAG) describe vortex liquid metal pump systems in which a magnetic field generated by a direct current sets the metal in motion, creating a pressure difference between an inlet and an outlet. This system is located outside a furnace, with the liquid metal being drawn from the furnace to an inlet of the vortex device and discharged from an outlet of the vortex device back into the furnace.

[0012] EP 2 375 206 (ZMAG) describes a system with moving mechanical parts, in which rotating permanent magnets create a flow of non-ferrous metal in a container equipped with spiral conduits. This system is installed within a furnace and allows molten metal from the furnace to be pumped out.

[0013] These non-ferrous liquid metal pumping systems have the disadvantage of requiring a spiral conduit or vortex system, which is difficult to manufacture from a refractory material resistant to the effects of the liquid metal. Furthermore, this spiral conduit or vortex system is subject to wear from contact with the liquid metal and must be replaced regularly. Other non-ferrous liquid metal pumping systems are described in documents WO 2022 / 24996 and JP 2021100765.

[0014] To simply create agitation within a bath of molten non-ferrous metal in a furnace, or in other words, to simply stir the molten metal in a furnace, a simpler and less expensive system would be desirable. A simpler system is described in WO 2024 / 048787 (ZMAG). It completely separates the magnetic system from the molten metal bath, with the magnetic system installed outside the furnace, without any connection or fluidic contact with the molten metal inside. This system comprises rotating permanent magnets that generate a rotating magnetic field acting on the molten metal bath through the furnace wall. This system effectively avoids the need for complexly shaped parts intended for contact with molten non-ferrous metal, which would otherwise have to be made of a refractory material.

[0015] However, in the system described in WO 2024 / 048787, the furnace wall (which is generally made of ferrous metal and has a ceramic refractory layer) significantly attenuates the magnetic field that must pass through it. To achieve satisfactory stirring, this attenuation must be compensated for by using large, high-induction permanent magnets. This means that while such a system avoids the use of expensive wear parts, this is offset by a very large initial investment in permanent magnets. For small furnaces, this investment can become prohibitive.

[0016] The present invention seeks to provide an electric furnace installation for non-ferrous liquid metal, with high energy efficiency and low loss on ignition, allowing good mixing of the liquid metal, which is suitable for relatively small quantities of metal, in particular between about half a ton and about fifteen tons, which does not require too high an investment cost, and which allows the integration of other functions such as the treatment of the liquid metal.

[0017] Objects of the invention

[0018] According to the invention, the problem is solved by a furnace installation having at least two fluidically connected zones, said furnace installation being equipped with purely electric heating means, including at least one electric immersion heater. Stirring of the molten metal is ensured by magnetic stirring. This provides highly efficient stirring, allowing the immersion heaters to be used with high electrical power, almost all of which is dissipated as heat in the molten metal bath.

[0019] A first object of the invention is a furnace installation for non-ferrous metals, in particular aluminium, magnesium, zinc, tin, lead, comprising at least one enclosure capable of containing liquid metal, and

[0020] - at least two zones for liquid metal in fluidic connection, as well as

[0021] - heating methods that are solely electric, and which include at least one immersion heater for heating the molten metal and possibly at least one radiant heat source for preheating the furnace,

[0022] - magnetic means for stirring the liquid metal, comprising at least one rotating permanent magnet, said magnetic stirring means being disposed in said enclosure, and / or below said enclosure, and / or on the side of said enclosure.

[0023] According to a first embodiment, the installation comprises a first zone for melting solid metal and a second zone for holding liquid metal. According to a second embodiment, which can be combined with the first embodiment, the installation comprises a first zone for melting solid metal and a second zone for processing liquid metal.

[0024] According to a third embodiment which can be combined with said first embodiment and / or with said second embodiment, said installation comprises a first zone for melting solid metal, a second zone for holding liquid metal, and a third zone for processing liquid metal.

[0025] According to a variant of this third embodiment, the said installation also includes a fourth zone for unloading the liquid metal.

[0026] According to a fourth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including with variants thereof, said installation includes at least one immersion heater located in said zone for melting solid metal.

[0027] According to a first variant of this fourth embodiment, the installation also includes at least one immersion heater in the holding zone. According to a second variant of this fourth embodiment, which can be combined with the first variant, the installation also includes at least one immersion heater in the zone for processing the molten metal.

[0028] According to a third variant of this fourth embodiment, which can be combined with its first and / or second variant, said installation includes a metal heating zone equipped with at least one immersion heater which is in direct fluidic connection with said zone for the treatment of liquid metal.

[0029] According to a fifth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including with a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or according to the second variant thereof, said magnetic stirring means are located in the melting zone.According to a sixth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including with a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or according to the second variant thereof, and / or with said fifth embodiment, said zones are delimited, within the same enclosure, by at least one wall comprising an opening, and / or correspond to two enclosures in fluidic connection.

[0030] According to a seventh embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including with a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or according to the second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, said installation comprises at least two enclosures in fluidic connection.According to an eighth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including with a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or according to the second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation comprises at least two enclosures in fluidic connection, and each zone corresponds to one enclosure.

[0031] According to a ninth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or according to the second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation, and / or with said eighth embodiment, said installation includes feeding means for supplying solid metal to said area for solid metal melting, said feeding means possibly including a conveyor.

[0032] According to a first variant of this ninth embodiment, said feeding means or said conveyor includes (includes) an electric preheating means for drying said solid metal.

[0033] According to a second variant of this ninth embodiment, which can be combined with said first variant and with all embodiments of the furnace installation, said feeding means comprise a vibrating funnel connected to a conveyor.

[0034] According to a third variant of this ninth embodiment, which can be combined with said first variant and / or with said second variant, and with all embodiments of the furnace installation, said feeding means comprise a presentation floor for the solid metal at the edge of the melting zone, optionally provided with a mechanical pushing means for transferring the solid metal presented on said floor into said melting zone.

[0035] According to a fourth variant of this ninth embodiment, which can be combined with said first variant and / or with said second variant and / or with said third variant, and with all embodiments of the furnace installation, said feeding means comprise a robot configured to depalletize a pallet of solid metal ingots.According to a tenth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation, and / or with said eighth embodiment, and / or with said ninth embodiment, said installation comprises a zone for melting solid metal provided with a magnetic stirring means designed to be capable of generating a vortex which keeps solid metal chips submerged during their melting.

[0036] According to an eleventh embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation, and / or with said eighth embodiment, and / or with said ninth embodiment, and / or with said tenth embodiment, said installation comprises at least one movable wall to delimit an area.

[0037] According to a twelfth embodiment, which may be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation, and / or with said eighth embodiment, and / or with said ninth embodiment, and / or with said tenth embodiment, and / or with said eleventh embodiment, at least one of said enclosures capable of containing liquid metal includes at least one closable opening to allow for the establishment, if necessary,a new fluidic connection with another enclosure capable of containing liquid metal or for releasing liquid metal from said enclosure.

[0038] According to a thirteenth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation, and / or with said eighth embodiment, and / or with said ninth embodiment, and / or with said tenth embodiment, and / or with said eleventh embodiment, and / or with said twelfth embodiment, said installation includes a metal outlet zone which includes at least one means for exiting liquid metal from said furnace installation.

[0039] In one variant, this means of removing liquid metal from said furnace installation is a means of withdrawing a determined quantity of liquid metal.

[0040] According to a fourteenth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, including a variant thereof, and / or with said fourth embodiment, possibly according to the first and / or second variant thereof, and / or with said fifth embodiment, and / or with said sixth embodiment, and / or with said seventh embodiment, said installation, and / or with said eighth embodiment, and / or with said ninth embodiment, and / or with said tenth embodiment, and / or with said eleventh embodiment, and / or with said twelfth embodiment, and / or with said thirteenth embodiment, said installation comprises a dosing zone, provided with a device for taking a controlled quantity of liquid metal.

[0041] A second object of the present invention is a process for melting non-ferrous metals in a furnace installation for ferrous metals according to the first object of the present invention, possibly according to its first and / or second and / or third and / or fourth and / or fifth and / or sixth and / or seventh and / or eighth and / or ninth and / or tenth and / or eleventh embodiment, in which process at least one of said immersion heaters in the melting zone is regulated so that said installation can supply liquid metal to an external consumer while said melting zone still contains solid metal.

[0042] According to a first embodiment, at least one of said immersion heaters is regulated in the melting zone so that said installation can supply liquid metal to an external consumer while said melting zone is supplied with solid metal.

[0043] According to a second embodiment which can be combined with the first embodiment, at least one of said immersion heaters is regulated in the melting zone so that the temperature of the liquid metal in the melting zone remains within an interval whose width does not exceed 40 °C, preferably does not exceed 25 °C, more preferably does not exceed 15 °C, and even more preferably does not exceed 10 °C.

[0044] According to a third embodiment, which can be combined with the first embodiment and / or with the second embodiment, the melting process is conducted such that the temperature of the liquid metal in the melting zone differs from that of the holding zone by more than 10 °C, and possibly by more than 20 °C. According to a first variant, the temperature of the liquid metal in the melting zone is at least 10 °C, and possibly at least 20 °C, higher than that of the holding zone.

[0045] According to a second variant, the temperature of the liquid metal in the melting zone is at least 10 °C lower than that of the holding zone, and possibly at least 20 °C lower.

[0046] According to a fourth embodiment, which can be combined with the first embodiment and / or with the second embodiment and / or with said third embodiment (and any variant thereof), at least one of said immersion heaters in the melting zone is regulated so that the temperature of the liquid metal in the melting zone remains within a range whose width does not exceed 40 °C, preferably not exceeding 25 °C, more preferably not exceeding 15 °C, and even more preferably not exceeding 10 °C. This regulation may, in particular, target the rotational speed and / or the direction of rotation of the rotating permanent magnet.

[0047] According to a fifth embodiment, which can be combined with the first embodiment and / or with the second embodiment and / or with said third embodiment (and any variant thereof) and / or with the fourth embodiment, the process is operated in such a way that the mass ratio between the quantity of solid metal introduced into the melting zone and the quantity of liquid metal present in the melting zone is less than 6, preferably less than 5, even more preferably between 2.5 and 4.5, and optimally between 2.7 and 4.0.

[0048] According to a sixth embodiment, which can be combined with the first embodiment and / or with the second embodiment and / or with said third embodiment (and any variant thereof) and / or with the fourth embodiment and / or with said fifth embodiment, said external consumer is a molding facility. According to an advantageous variant, this molding facility comprises a molding machine, preferably a die-casting machine, said molding machine comprising a permanent mold.

[0049] According to a seventh embodiment, which can be combined with the first embodiment and / or with the second embodiment and / or with said third embodiment (and any variant thereof) and / or with the fourth embodiment and / or with said fifth embodiment and / or with said sixth embodiment, at least one of said magnetic mixing means is also regulated.

[0050] A third object of the present invention is a foundry installation for the manufacture of molded parts using at least one mold, comprising a furnace installation for non-ferrous metals according to the first object of the invention, possibly according to its first and / or second and / or third and / or fourth and / or fifth and / or sixth and / or seventh and / or eighth and / or ninth and / or tenth and / or eleventh embodiment, and further comprising at least one molding installation which is fed by said furnace installation via a fluidic link.

[0051] According to a first embodiment, said fluidic link has a length of less than ten meters, and preferably less than five meters, more preferably less than three meters, and even more preferably less than two meters, this length being measured from the exit of the enclosure of said furnace installation to the entrance into said molding installation.

[0052] According to a second embodiment which can be combined with said first embodiment, said foundry installation has a means of controlling the supply of solid metal to the furnace installation which is controlled by a computer machine configured to use for this control information representing the consumption of liquid metal by said molding installation.

[0053] According to a third embodiment which can be combined with said first embodiment and / or with said second embodiment, said mold is a permanent mold.

[0054] According to a fourth embodiment which can be combined with said first embodiment and / or with said second embodiment and / or with said third embodiment, said molding installation is an injection molding installation.

[0055] A fourth object of the present invention is a method of operating a foundry installation according to the third object, wherein said molding installation is operated to manufacture castings while the melting zone of said furnace installation is fed with solid metal.

[0056] According to a first embodiment, said molding installation is supplied with liquid metal from said furnace installation by a means selected from the group formed by:

[0057] (i) a scooping ladle,

[0058] (ii) an automatic dosing system, and in particular an automatic dosing system whose lower part is immersed in the bath and which allows a controlled quantity of liquid metal to be taken and introduced directly into the mold or into the injection chamber of the piston of the injection molding machine,

[0059] (iii) a dosing pump, part of which is permanently immersed in the bath and which allows a controlled quantity of liquid metal to be introduced directly into the injection chamber of the injection molding machine piston,

[0060] (iv) a liquid metal sampling system of the "dosing pipette" type connected to a mechanical arm for filling the piston chamber of the injection molding machine. According to a second embodiment, which can be combined with said first embodiment, the process is operated such that the mass ratio between the quantity of solid metal introduced into the melting zone and the quantity of liquid metal present in the melting zone is less than 6, preferably less than 5, even more preferably between 2.5 and 4.5, and optimally between 2.7 and 4.0.

[0061] Brief description of the figures

[0062] The figures are provided for illustrative purposes and to better explain certain technical features of the invention, so as to enable a person skilled in the art to carry out the invention. They are not intended to, nor do they have the effect of, limiting the scope of the invention.

[0063] [Fig. 1] schematically represents a top view of an installation according to a first embodiment of the invention.

[0064] [Fig. 2] schematically represents a side view of the furnace of [Fig. 1] in section along the section line A-A'.

[0065] [Fig. 3] schematically represents a top view of an installation according to a second embodiment of the invention.

[0066] [Fig. 4] schematically represents a side view of the oven of [Fig. 3] in section along the cutting line B-B'. [Fig. 5] schematically represents a cross-section of a magnetic stirring system usable for the implementation of the present invention.

[0067] [Fig. 6] refers to [Fig. 5] and schematically represents the plate with its permanent magnets.

[0068] [Fig. 7] schematically represents a side view of an oven usable for the realization of the present invention in section; it is a variant with a lid.

[0069] [Fig. 8] schematically represents a top view of an installation according to a variant of the invention.

[0070] [Fig. 9] schematically represents a top view of an installation according to a third embodiment of the invention.

[0071] [Fig. 10] schematically represents a perspective view of the installation according to the

[0072] [Fig. 9],

[0073] [Fig. 11] shows a schematic perspective view of an enclosure that can be used without an installation according to a fourth embodiment of the invention.

[0074] [Fig. 12] shows another schematic perspective view of the enclosure according to [Fig. 11], [Fig. 13] shows a schematic perspective view of an installation according to a fifth embodiment.

[0075] [Fig. 14] shows a schematic top view of the installation according to [Fig. 13],

[0076] [Fig. 15] shows a schematic perspective view with lid of a fusion chamber usable for implementing the invention.

[0077] [Fig. 16] shows a schematic perspective view of the fusion chamber according to [Fig. 15], without a lid.

[0078] [Fig. 17] shows a schematic perspective view of a cross-section of a furnace installation according to the invention which was used for the examples.

[0079] [Fig. 18] shows a schematic perspective view of a cross-section of the installation of [Fig. 17], at a preheating stage with radiant heating elements. [Fig. 19] refers to Example 1 and shows a temperature reading of the liquid metal bath during the introduction of batches of solid metal.

[0080] [Fig. 20] schematically shows a foundry installation for the manufacture of castings according to the invention.

[0081] The following reference numerals are used in the figures and in the description: 1, 100, 200, 300, 500, 700 - Furnace installation according to the invention; 2, 102, 202, 302, 402, 502, 602, 702 - Enclosure

[0082] 3,103,203; 4,104,204 - External wall (3,103,203 long; 4,104,204 short) 5,105,205,405,704 - Internal wall 6,106,406,606 - Opening in the internal wall 5,105,405,605

[0083] 7,107,307,407,507,607,707 - Immersion heater

[0084] 8,108,208,608,708 - Magnetic mixing system

[0085] 9, 109, 209, 409, 509 - Metal processing system

[0086] 11 - Base of 2.102

[0087] 12.112 - Injector of 9.109

[0088] 315,715 - Superstructure

[0089] 16,316,516 - Lid

[0090] 17, 217, 417, 517, 617 - Outlet (or inlet) chute

[0091] 218,718 - Radiant heating device (preheating of the enclosure)

[0092] 350, 450, 650, 750 - Lifting device

[0093] 460,560 - Liquid metal dosing device (pump)

[0094] 752 - Thermocouple

[0095] 670 - Scrap introduction zone

[0096] 671 - Ingot introduction zone

[0097] 572 - Melting Zone

[0098] 573 - Maintenance Zone

[0099] 574 - Liquid Metal Processing Area

[0100] 575 - Heating zone

[0101] 576 - Unloading area (dosing area)

[0102] 80 - Engine

[0103] 81 - Axis

[0104] 82 - Guidance System

[0105] 83 - Platinum

[0106] 84.85 - Permanent magnets (of opposite polarity)

[0107] 86 - Waterproof envelope

[0108] 590 - Vibrating conveyor

[0109] 591 - Heated Tunnel

[0110] 592 - Hopper

[0111] 594 - Skip loading and unloading facility (595: Skip)

[0112] 596 - Ingot loading facility in the smelting area 572

[0113] 1000 - Foundry installation for the manufacture of castings according to the invention

[0114] 1010 - Oven installation according to the invention

[0115] 1011 - Enclosure

[0116] 1012 - Inner wall

[0117] 1013 - Magnetic stirring system 1014 - Metal processing system

[0118] 1015 - Liquid metal dosing device (pump)

[0119] 1016 - Immersion heater

[0120] 1020 - Molding Installation

[0121] 1021 - Molding Machine

[0122] 1022 - Permanent Mold

[0123] 1030 - Fluidic connection between 1010 and 1020

[0124] Detailed description

[0125] The invention relates to a furnace installation for non-ferrous metals, in particular aluminum, magnesium, zinc, tin, and lead, where the term "metal" here always includes alloys based on that metal. This furnace installation comprises at least two liquid metal zones that are separated but connected by a fluidic system. In this installation, a zone may correspond to a chamber, and / or a chamber may contain several zones.

[0126] In one embodiment, the installation comprises at least one enclosure and at least one internal wall contained within at least one of these enclosures, said wall delimiting at least two zones that are separated but fluidically connected. In another embodiment, the installation comprises two fluidically connected enclosures. To increase the number of zones, if desired, one or both of these enclosures may have one or more internal walls. These two embodiments may be combined.

[0127] The installation may include more than two zones which are separate but are in fluidic connection, typically arranged in series; it may, for example, include three zones.

[0128] A first area can be set up as a melting zone. To supply the melting zone with solid metal to be melted, the installation may include means for introducing solid metal into the melting zone. These means may include a conveyor.

[0129] A second zone can be designated as a liquid metal holding zone. Optionally, or in addition, at least one zone can be designated as a liquid metal treatment zone. If this liquid metal treatment zone is neither the melting zone nor the holding zone, the liquid metal treatment zone(s) can be functionally located between the melting zone and the liquid metal holding zone. The liquid metal treatment zone can be designated as a gas treatment ladle. A gas treatment ladle aims to remove hydrogen, in particular, by injecting an inert gas (typically argon) or a reactive gas (typically chlorine, although this process is effective but outdated for environmental reasons) into the liquid metal. The treatment zone (or another treatment zone) can be designated as a liquid metal filtration ladle using a ceramic filter.These liquid metal processing technologies are known as such and will not be described in greater detail here.

[0130] The inner wall may extend from a level above the liquid metal level of the enclosure to the bottom of the enclosure, or it may stop above the bottom of the enclosure, leaving a space for the liquid metal to flow through. It may also allow the metal to pass through laterally. The wall may have one or more openings for the metal to flow through.

[0131] The enclosure may include one or more solid metal loading zones. It may include a liquid metal inlet. It may include a liquid metal outlet. It may include a liquid metal processing chamber, in particular a liquid metal degassing chamber. It may include a liquid metal filtration chamber.

[0132] According to a first essential feature of the invention, the furnace installation according to the invention comprises heating means that are exclusively electric. More specifically, it comprises at least one electric immersion heater, and typically a plurality of immersion heaters, located within at least one enclosure, or within at least one of the enclosures. An enclosure may comprise several electric immersion heaters. A zone may comprise one or more immersion heaters, but depending on its use, each zone does not need to include an immersion heater. The immersion heaters are used as the sole heat source of the installation, except, in one embodiment, for the use of radiant heat sources to preheat the furnace for dry starting.Electric immersion heaters allow for an energy efficiency of approximately 99%, meaning that almost all the electrical energy consumed is transformed into usable heat to heat the oven installation.

[0133] Preferably, an immersion heater with an external diameter of at least 50 mm, preferably at least 55 mm, even more preferably at least 60 mm, or even at least 65 mm or at least 70 mm, should be used. Such immersion heaters are commercially available. They advantageously include a ceramic sheath. SisIXL is preferred for this purpose as it is sufficiently inert in contact with liquid metal, particularly aluminum, zinc, lead, tin, and magnesium. Compared to other usable ceramic materials, it offers high resistance to thermal shock and good mechanical strength.

[0134] Preferably, immersion heaters are designed to be capable of delivering a thermal power of at least 25 watts per cm². 2 of external surface, preferably at least 30 W / cm² 2 , more preferably of at least 35 W / cm 2 and even more preferably at least 40 W / cm² 2 .

[0135] Advantageously, the furnace installation according to the invention is operated in a quasi-isothermal manner, meaning that the temperature of the liquid metal remains as constant as possible throughout the operation of the installation. In particular, the amount of energy supplied by the heating means, which are electric immersion heaters, is the same as the enthalpy of fusion required to melt the solid metal fed into the installation. This requires effective mixing of the bath. This mixing distributes the heat transmitted by the immersion heaters throughout the bath, thereby increasing the thermal power delivered by the heaters. This accelerates the melting process, shortens the holding time, and increases the furnace throughput (expressed as the quantity of metal per unit time). This allows for a reduction in the overall size of the installation, which in turn reduces heat loss.

[0136] These immersion heaters are advantageously straight. In specific situations, it may be advantageous to use an immersion heater that is not straight, and which may, for example, have an "L" shape. As an example, the "L" shape is advantageously used in a holding zone.

[0137] In a particular embodiment of the invention, the furnace installation includes radiant electric heating devices for preheating the chamber. Advantageously, modified immersion heaters, straight or not (for example, L-shaped), are used, which are equipped with a steel casing (advantageously made of steel with a high thermal emission coefficient). Their power is typically around 10 kW. These devices are advantageously retractable. The chamber is preheated by radiant and convective heating.

[0138] According to a second essential feature of the invention, the furnace installation comprises at least one magnetic stirring system. This magnetic stirring system includes a system of permanent magnets capable of being set in motion. This movement of the permanent magnets transmits a moving magnetic field to the molten metal. In a particularly advantageous embodiment, the magnetic stirring system comprises a rotating element designed to rotate about a central axis. A first magnet is fixed to this rotating element, its upper face being the N-pole, and a second magnet is fixed to this rotating element, its upper face being the S-pole. The rotation of this rotating element induces eddy currents within the liquid metal, which generate a mechanical motion of the liquid metal.

[0139] This magnetic stirring system is preferably installed inside the enclosure containing the liquid metal; alternatively, it can be installed below the enclosure containing the liquid metal. The enclosure equipped with a magnetic stirring system is advantageously one that includes an electric immersion heater. The area equipped with a magnetic stirring system is advantageously one that includes an electric immersion heater. The permanent magnet magnetic stirring system provides very efficient mixing of the bath, which is necessary to ensure temperature homogenization in the presence of significant localized heat input from the immersion heaters. The absence of mechanical stirring elements in contact with the bath reduces maintenance costs by eliminating mechanical parts subject to wear and prevents bath contamination from the gradual dissolution of these mechanical elements.

[0140] When the stirring system is installed inside an enclosure, the permanent magnets are housed in a liquid-metal-tight casing. This casing can be made of a non-metallic material, preferably ceramic. Its shape can be approximately cylindrical. Such a casing offers several advantages. A cylindrical ceramic component is easy to manufacture compared to the complex shapes of the vortex systems found in known magnetic stirring systems. This is a significant point, as it is a wear part. This refractory casing can be made with a relatively thin wall. A ceramic material, and especially a thin ceramic material, does not significantly attenuate the magnetic field of the permanent magnets, unlike the state-of-the-art systems mounted against the outer wall of the furnace.The system according to the invention can therefore use smaller permanent magnets than prior art systems, resulting in significant cost savings.

[0141] Compared to existing electromagnetic mixing systems, a magnetic mixing system with rotating permanent magnets is significantly more compact, easier to install, and consumes less electrical energy. The furnace installation according to the invention can be modular. For example, internal walls can be added within an enclosure to delimit a new zone. At least one enclosure can also be provided with at least one closable opening, allowing for the addition, if necessary, of a new fluid connection to another enclosure, whether already part of the furnace installation or added later.This modularity allows the furnace operator to meet new needs. For example, if a metal treatment zone was not initially planned, it is possible, if the size of the holding zone allows, to define a new zone by adding one or more walls within the holding zone; this new zone can then be configured as a treatment zone. Similarly, it is also possible to add an additional chamber to the furnace installation by establishing a fluid connection from a closable opening initially provided in one of the installation's chambers to an opening in the additional chamber. This fluid connection (which typically leads from the existing holding zone to the new treatment zone) can be made using known types of molten metal transfer chutes.The said closable opening in the enclosure can also be used to add, if needed, a liquid metal outlet.

[0142] The fluidic connections between two enclosures and / or between the furnace installation and the molding installation can be known type liquid metal transfer chutes.

[0143] The invention will now be explained in detail with reference to the figures.

[0144] Figure 1 shows a first embodiment of a furnace installation 1 according to the invention, viewed from above. This figure does not show the superstructure and covers that are normally present when the furnace is in operation. Figure 2 shows the same furnace installation in vertical section along line A-A' of Figure 1. The furnace installation 1 comprises a chamber 2. On Figure 2, a horizontal dashed line indicates the maximum level of the molten metal. The chamber 2 comprises a bottom 11, two long outer walls 3a, 3b that are opposite and substantially parallel, and two short outer walls 4a, 4b that are opposite and substantially parallel. The shape of the chamber is substantially rectangular in both the top and side views, but the chamber can be made in different shapes, in particular with slightly inclined and flared side walls, or with curved walls.

[0145] The enclosure 2 also includes an internal wall 5 that divides the internal volume of the enclosure into two zones I and II. In this embodiment, this wall does not extend to the bottom of the enclosure, so that the two zones I and II are fluidically connected by an opening 6 located at the bottom of the enclosure. In a variant, the wall may extend to the bottom and include a lateral opening or an opening positioned otherwise.

[0146] Another enclosure geometry is shown in [Fig. 3] in top view and in [Fig. 4] in section AA. [Fig. 3] also does not show the superstructure and covers that are normally present when the furnace is in operation. Compared to [Fig. 1] and [Fig. 2], the numerical references denoting the same aspect are increased by 100. In this embodiment, the external walls 104a, 104b are not vertical but slightly inclined. The internal wall extends to the bottom of the enclosure 102, and the fluidic connection between zones I and II is made through a lateral opening 106. The enclosure according to the invention comprises at least one immersion heater 7, 107, and preferably a plurality of immersion heaters. In [Fig. 1] and [Fig. 2], the external walls 104a, 104b are not vertical but slightly inclined. The internal wall extends to the bottom of the enclosure 102, and the fluidic connection between zones I and II is made through a lateral opening 106. The enclosure according to the invention comprises at least one immersion heater 7, 107, and preferably a plurality of immersion heaters. In [Fig. 1] and [Fig. 2], the internal walls 104a, 104b are shown in section AA. 2] These immersion heaters are all located in the same zone I of the enclosure, but they could be located in zone II, or both in zone I and in zone II as is the case in the variant shown in the [Fig.3] and [Fig. 4].

[0147] The enclosure advantageously includes a magnetic stirring system 8,108 located inside said enclosure, as shown in [Fig. 1] to [Fig. 4]. It will be explained in greater detail below. The enclosure as shown in [Fig. 1] to [Fig. 4] also includes at least one metal processing system 9,109. In [Fig. 1] to [Fig. 4], this system is a degassing system comprising a rotor equipped with an injector 12,112 for injecting an inert gas; these systems are known as such and will not be described in greater detail here.

[0148] The installation according to the invention may also include at least one metal treatment system, such as a filtration system. This system may be located in an area that does not have immersion heaters, as in [Fig. 1] and [Fig. 2], or it may be located in an area that has at least one immersion heater as in [Fig. 3] and [Fig. 4].

[0149] The magnetic stirring system 8,108 comprises at least one permanent magnet capable of movement. Preferably, this movement is rotational about an axis. If the magnetic stirring system is intended to be placed inside an enclosure, the permanent magnet is disposed within a liquid-metal-tight casing. This casing can be made of a non-metallic material, for example, a suitable ceramic material; the thickness of this casing can be quite small, on the order of 20 mm at most, and preferably not exceeding 15 mm. Figures 5 and 6 show two views of a magnetic stirring system 8,108 suitable for achieving the object of the invention. It comprises a plate 83, here substantially cylindrical in shape, which carries at least two permanent magnets of opposite polarity 84, 85. In this case, said plate 83 carries two pairs of permanent magnets 84a, 84b; 85a, 85b of opposite polarities.The plate 83 is configured to be able to perform a rotational movement around an axis 81 within a guide system 81. A motor 80 is configured to move said axis 81. The motor 80, the axis 82, the guide system 82, the plate 83 and the permanent magnets 84, 85 are housed in a sealed enclosure 86.

[0150] Preferably, the magnetic stirring system is located in an area that also contains at least one immersion heater 7,107, as shown in [Fig. 1] to [Fig. 4]. Stirring the molten metal bath near an immersion heater improves heat dissipation and thermal homogenization within the furnace area and, more generally, throughout the furnace. It also helps to homogenize the chemical composition of the bath and prevent the settling of intermetallic phases. Stirring the bath allows for greater electrical power dissipation in the immersion heater, thus shortening the heating time.

[0151] The enclosure 2 according to the invention advantageously comprises a superstructure (not shown in [Fig. 7] but in [Fig. 9], item 315), which can be designed to support the various systems mentioned above (not shown in Figure 7), namely, in particular, the immersion heaters 7 and the rotor of the metal treatment system 9. The superstructure includes movable or removable covers 16 that close the furnace. The furnace installation may also include a system for introducing solid metal, for example, a conveyor (not shown in this figure).

[0152] The enclosure may include a liquid metal outlet chute 17, as also shown in [Fig. 7]. This chute may be located in a metal outlet zone III, separated from another zone II located upstream by an internal wall 5b. The enclosure may have other geometries. It may include a plurality of walls 5 delimiting a plurality of zones; this is shown in [Fig. 7] and especially in [Fig. 8].

[0153] Figure 8 shows an advantageous embodiment of a furnace installation according to the invention. It comprises a chamber 202 having three internal walls 205a, 205b, 205c delimiting four zones: a melting zone I, a holding zone II, a liquid metal processing zone III, and a liquid metal outlet zone IV. The liquid metal can be discharged, in particular, by suction or (as in the figure) by pouring through a chute 217 provided in a wall 204b of the chamber 202. Optionally, the furnace may also include a ceramic filter (not shown in the figures). This ceramic filter can be located in the wall separating the metal processing zone III from the metal outlet zone IV. The four zones are fluidically connected; the openings in the internal walls 205 are not shown in Figure 8, but the metal flow is indicated by arrows.

[0154] This installation, as shown in [Fig. 8], includes a plurality of electric immersion heaters 207, notably in the melting zone I, the holding zone II, and the liquid metal treatment zone III. It also includes a magnetic stirring system 208 in the melting zone I; this is the zone where stirring is of greatest interest as it accelerates melting and thus increases the furnace throughput (or, in other words, the furnace's melting capacity expressed as the quantity of molten metal per unit time).

[0155] As can be seen in [Fig. 8], the furnace installation according to the invention may also include one or more devices 218 capable of preheating the internal walls of the chamber by radiation. These devices are preferably retractable. They are used when the furnace is started from a temperature significantly below the melting point of the metal, or even from a cold start. They can be arranged horizontally (as in [Fig. 8]) and / or vertically.

[0156] Figures 9 and 10 show a perspective view and a top view, respectively, of a furnace installation according to another embodiment of the invention. This installation consists of three chambers 302a, 302b, and 302c connected by a fluidic system. In this embodiment, two of the chambers (namely chamber I with the numerical designation 302a and chamber II with the numerical designation 302b) are configured as melting zones; they can be used simultaneously or alternately. Zone III with the numerical designation 302c is the holding zone.

[0157] These figures show a portion of the superstructure 315 that was omitted in [Fig. 2], [Fig. 4] and [Fig. 7]. In particular, [Fig. 9] shows a portion of the lifting devices 350 for lifting the covers 316a, 316b of the enclosures 302a and 302b, and for removing the immersion heaters 307. The cover 316c of the enclosure 302c comprises two parts 316c1 and 316c2 that can be opened separately, each being equipped with its own motor 351-1 and 315-2.

[0158] A furnace according to [Fig. 9] and [Fig. 10] can be made for example with a melting capacity of 2 x 750 kg / hour and a holding capacity of 3,500 kg, with a heating power of 2 x 30 kW for the melting zones and 60 kW for the holding zone; the energy consumption is about 30 to 40 kWh in holding mode, and 560 kWh in melting mode at a rate of 15,000 kg / hour.

[0159] In a variant not shown in the figures, the holding chamber is divided into two zones by adding a partition wall. One zone can act as a treatment zone, the other as a holding and drawing zone. This reconfiguration is facilitated by the two-part lid, which allows a gas treatment rotor to be inserted into one of the zones, while the other remains closed.

[0160] Figures 11 and 12 show, respectively, a perspective view and a top view of a chamber 402 that can be used in a furnace installation according to another embodiment of the invention. This chamber 402 is subdivided into three zones I, II, and III: a first zone I for holding the molten metal, a second II for processing the metal, and a third III for discharging the molten metal. It should be noted that in this chamber, the metal processing zone does not have immersion heaters. This can be advantageous when rotors are used to introduce inert gas into the molten metal, because the slight local overheating generated by immersion heaters can reduce the lifespan of the rotors. In this case, immersion heaters are provided in an adjacent zone connected to the processing zone.

[0161] In Figures 11 and 12, zone I shows an inlet chute 417a for the liquid metal coming from a melting chamber (i.e., a chamber with a melting zone), as well as four immersion heaters. The liquid metal is transferred through a passage 406 at the bottom of the chamber 402 to the processing zone II, which is equipped with a rotor, the motor 409 of which is shown in the figures. The discharge zone III (also called the "dosing zone") includes a liquid metal pump capable of drawing a predetermined quantity of liquid metal, which leaves the chamber 402 through an outlet chute 417b to a consuming device (not shown in the figures), which may be a casting machine. This discharge zone III is heated by three immersion heaters 407.

[0162] This enclosure may include a magnetic mixing device (not shown in the figures); its presence in the melting chamber is mandatory. The enclosure according to [Fig.

[0163] [Fig. 11] and [Fig. 12] could obviously represent a complete installation according to the invention if the immersion heaters in zone I are sized to have sufficient thermal capacity to melt a sufficient quantity of metal; in this case, zone II or zone III can be subdivided by adding at least one internal wall to create a holding zone. As shown in [Fig. 11] and [Fig. 12], this enclosure does not have a melting zone; it can be coupled to another melting enclosure. Such a melting enclosure will be shown below in relation to [Fig. 15] and [Fig. 16].

[0164] Figures 13 and 14 show, respectively, a perspective view and a top view of a furnace installation 500 according to another embodiment of the invention. This installation comprises two enclosures. The flow of liquid metal is indicated by three arrows. The first enclosure is a melting chamber 502a, with its magnetic stirring device (not shown in Figures 13 and 14) immersed in the liquid metal bath and with its immersion heaters (in this case, thirty immersion heaters). This melting chamber 502a has a melting zone 572 and is in fluidic connection with a second chamber 502b, which is subdivided into several zones by walls. A first zone 573 is a holding zone. A second zone is a liquid metal treatment zone 574 by inert gas injection. A third zone

[0165] 575 is a heating zone, equipped with immersion heaters, noting that the treatment zone does not include immersion heaters in this example. A fourth zone

[0166] 576 is a liquid metal discharge zone. The heating zone 575 is separated from the processing zone 574 and the discharge zone 576 by internal walls with openings (not shown in the figures) to maintain fluid connection with said zones. The discharge zone 576 includes a liquid metal dosing device 560, such as a pump.

[0167] The furnace installation 500 further includes, upstream of the melting chamber, a skip loading and unloading facility 594. This area comprises a skip yard, typically containing solid metal waste (e.g., molding scrap or compacted stamping skeletons), which is emptied into a hopper 592 connected to a solid metal conveying and preheating area. The hopper empties onto a vibrating conveyor 590 (typically a conveyor) located in a tunnel 591 heated by an electric heater. This conveyor empties the solid metal into the loading area of ​​the melting chamber. The installation also includes a second loading facility 595 near the melting chamber 502a, which can be used for ingots.

[0168] Figures 15 and 16 respectively show a representation with a lid (Fig. 15) and without a lid (Fig. 16) of a melting chamber 602 comprising a zone 670 specifically adapted for melting chips, allowing chips to be introduced in compacted form or even in bulk. The problem with introducing chips into a molten metal bath is that the chips must remain immersed in the liquid metal, whereas they tend to float; due to their small size or thinness, they are susceptible to oxidation in the air, leading to the formation of oxide dross. This oxide dross is lost in the metal balance; those skilled in the art refer to it as "loss on ignition."

[0169] As can be seen in [Fig. 16], the semicircular introduction zone of the scrap 670 is located outside the main enclosure, to which it is fluidically connected via two openings 606a, 606b. These openings allow the passage of a vortex of liquid metal generated by a magnetic soldering unit 608 located inside the main enclosure. A plurality of immersion heaters 607 heat the liquid metal bath. The liquid metal can leave the melting enclosure 602 via a suitable fluidic connection 617 (for example, a chute) towards a holding enclosure (not shown in this figure). This holding enclosure can, for example, be that of [Fig. 11] and [Fig. 12]. In this embodiment, the magnetic soldering unit 608 is located near the immersion heaters 607.

[0170] Alternatively, the magnetic stirring unit 608 can be located in the area of ​​the melting chamber 670 specially adapted for melting chips, or below this area of ​​the melting chamber 670 specially adapted for melting chips; this latter embodiment is visible in [Fig. 21]. The vortex of liquid metal created in this melting chamber 670 specially adapted for melting chips can be sufficient to ensure effective stirring of the metal around the immersion heaters 607 located in the main chamber.

[0171] The enclosure 602 of [Fig. 15] and [Fig. 16] also includes an ingot introduction zone 671, in the form of an inclined plate acting as a slide; a conveyor can be connected to this zone, as in the previous example of [Fig. 13] and [Fig. 14],

[0172] The melting chamber of this embodiment represents a modular unit that can be added to a furnace installation according to the invention which does not yet have a melting zone (such as that of [Fig. 11] and [Fig. 12]), in order to make it more versatile, or it can replace an ingot melting unit.

[0173] Figures 17 and 18 present yet another embodiment of the invention. This furnace installation 700 was used to generate the examples described below. It comprises an enclosure 702 subdivided by an internal wall 704 into two zones 1 and 11, namely a melting zone I and a holding zone II. These two zones are fluidically connected by two openings in the internal wall. The installation is modular and its internal layout can be modified by adding and rearranging the internal walls and by adding devices. The lifting device 750 is identified as being able to move the superstructure elements 715, which include the immersion heaters 707, the radiant heating elements 718 for preheating the furnace (see Figure 18), and the magnetic stirring system 708 installed when the furnace is loaded (see Figure 19).

[17] The holding zone here includes a series of 752 thermocouples which are necessary to conduct the experiments described below. During preheating, the furnace may be empty or may contain a small load of solid metal.

[0174] The installation according to the invention offers numerous advantages. It uses only electrical energy. It exhibits high energy efficiency, thanks to effective stirring. It can be started dry, without a bath base. Oxidation of the molten metal (and therefore loss on ignition) is minimized because heating occurs only within the bath, and the air temperature above the bath remains lower than the bath temperature. Furthermore, the melting process by adding solid metal to the bath can be rapid due to the high heat input from the immersion heaters, coupled with the rapid dissipation of this heat through effective stirring. Thanks to this rapid dissipation of heat from the immersion heater, the heater's power can be increased without fear of localized overheating of the metal or the heater itself.The combination of electric immersion heating (immersion heater) and magnetic stirring allows for high temperature homogeneity and stability. At a fixed point in the furnace, the bath temperature can be stabilized within a range of 4°C, or even 3°C or 2°C, in the absence of solid metal in the bath. In a continuous feed process (i.e., a process where solid metal is introduced into the furnace installation simultaneously with the removal of liquid metal, or where the bath still contains solid metal), the range depends on the rate of solid metal introduction. In the preferred case of constant feed, a range of less than 15°C, less than 10°C, less than 5°C, or even less than 3°C can be achieved.This constant feed can be achieved, in particular, by regularly introducing pieces of solid metal, such as ingots or scrap metal, into the melting zone. This introduction can be done in batches or, preferably, individually, for example, using a conveyor. In a batch process, the temperature range depends on the quantity of solid / liquid and can be less than 20°C, even reaching 15°C, but rarely lower.

[0175] For a given metal flow rate, the installation according to the invention can be more compact because the dilution ratio during the melting of solid metal (i.e. the amount of bath required to melt 1 tonne of solid metal per hour) can be reduced to a value less than 3.5, whereas in electric remelting furnaces according to the prior art this ratio is in the order of about 6 to about 8.

[0176] Another advantage is that the furnace refractory lifespan is improved compared to a gas furnace because, in the installation according to the invention, the air temperature is lower than that of the bath. The quality of the liquid metal is preserved because the stirring process does not introduce impurities, and because the temperature is more homogeneous within the bath. The installation allows for the melting of ingots, production waste, and compacted scrap (such as chips, cutting offcuts, and stamping skeletons), and the feeding of solid metal can be automated.

[0177] Another advantage of the furnace installation according to the invention is its modularity. As shown in [Fig. 9] and [Fig. 10], such an installation can comprise a plurality of individual chambers connected by a fluidic system. It can, in particular, include one or more metal processing zones. The size of the installation can be optimized for a given application, for example, alongside an injection molding press dedicated to a specific type of part. The modularity facilitates the use of standard components, such as standard-sized chambers.

[0178] The furnace installation according to the invention can be implemented in numerous variations, which can be combined to the extent that this is technologically feasible and relevant. In particular, and as already mentioned, it can have different geometries. Viewed from above, the enclosure can, for example, be rectangular or square, or it can be a shape other than a parallelepiped, or it can be L-shaped, H-shaped, or any other shape, for example, curved or semicircular.

[0179] The furnace installation according to the invention has numerous applications in the field of non-ferrous metal casting. It is particularly applicable to the casting of aluminum and its alloys. One specific use is in a melting zone. A melting zone is an area containing a liquid bath into which solid metal is loaded to melt it. This process can be quite slow. The electrical power dissipated in the immersion heater is limited by the heat transfer between the heater and the metal bath; this transfer is all the more efficient when the bath is vigorously stirred. This cannot be easily achieved with mechanical stirring methods if the bath is clogged with solid metal in the form of ingots, chips, or compacted stamping skeletons.The use of a magnetic stirring system located inside the chamber facilitates this stirring, even when the bath height is low, i.e., in the initial phase of melting. Thus, the furnace installation according to the invention makes it possible, in certain cases, to improve heat transfer and to melt solid metal more quickly in a bath of liquid metal.

[0180] A particular application is that of a melting process using at least one electric immersion heater in which melting is initiated without a bath, that is, without liquid metal, solely with a charge of solid metal (which may include ingots and / or solid products to be recycled). This process is the only known method for starting an electric melting furnace dry, without a liquid bath and without the input of heat generated by combustion.

[0181] In this process, the internal walls of the enclosure (or the area of ​​the enclosure in which this melting will take place) are advantageously preheated using devices emitting radiation, typically infrared radiation. These devices are advantageously electrical devices; they are advantageously retractable, as described in relation to [Fig. 8].

[0182] The solid charge in the furnace is heated using one or more immersion heaters, for example, according to the process described in WO 2013 / 199257 on behalf of the applicant. In this process, the immersion heater is preferably placed in physical contact with solid metal to enhance heat transfer through a strong conduction component, in addition to convection and radiation. The electrical power supplied to the immersion heater should be low, representing a fraction of the rated power, for example, less than 10% of the rated power; this power can then be gradually increased. When the metal begins to melt, it flows to the lowest point of the chamber, which may no longer be in contact with the immersion heater. When the bath level is very low, mechanical stirring is ineffective, while magnetic stirring works well.

[0183] Another advantage of the non-ferrous metal furnace according to the invention is its compact size. Indeed, for a given metal output, this furnace can be smaller than those of the prior art. This is due to the fact that isothermal melting allows liquid metal to be drawn off simultaneously with the addition of solid metal to be melted. The melting process can be operated in such a way that the mass ratio between the quantity of solid metal introduced into the melting zone and the quantity of liquid metal present in the melting zone is less than 6, preferably less than 5, even more preferably between 2.5 and 4.5, and optimally between 2.7 and 4.0.

[0184] This ratio is known as the "dilution ratio." For example, this means that to melt 1 tonne of aluminum per hour, the melting zone must contain between approximately 2.7 tonnes and approximately 4.0 tonnes of liquid aluminum. Also for aluminum, the installation can be sized and operated, for example, to melt 0.5 t / h of solid metal in 1.51 tonnes of liquid metal in the melting zone, or 1 t / h of solid metal in 31 tonnes of liquid metal, or 2 t / h of solid metal in 61 tonnes of liquid metal.

[0185] The compact design of the furnace installation according to the invention, and the absence of gas supply lines, allows it to be installed in the immediate vicinity of casting machines for the production of molded parts, for example, by die-casting processes. The furnace installation according to the invention can thus be operated within a foundry installation for the production of molded parts using at least one mold, in which said furnace installation supplies a molding installation (comprising a casting machine) with liquid metal. This supply is achieved via a fluid connection that can be very short. Its length, measured from the outlet of said furnace installation to the inlet of said molding installation, is typically less than ten meters, and preferably less than five meters, more preferably less than three meters, and even more preferably less than two meters.

[0186] Figure 20 schematically illustrates a foundry installation 1000 for manufacturing castings according to the invention. It comprises a furnace installation 1010 according to the invention, which supplies, via a fluidic connection 1030, a molding installation 1020. This molding installation includes a molding machine 1021 and possibly peripheral equipment necessary and useful for operating a molding machine, such as robots for handling the castings and cooling systems. The molding machine 1021 includes at least one permanent mold 1022. It may be an injection molding machine. The furnace installation 1010 may be an installation according to any of the described embodiments, or it may differ from these embodiments. It must have at least one enclosure 1011 and include at least two zones.In particular, it includes means of electric heating, and advantageously at least one immersion heater 1016 disposed in the melting zone, as well as a magnetic stirring system 1013, preferably disposed inside an enclosure 1011 of the furnace installation, and even more preferably in the melting zone.

[0187] The said furnace installation 1010 may also include a liquid metal processing system 1014. Advantageously it includes a liquid metal dosing device 1015 such as a liquid metal pump, capable of delivering a determined quantity of liquid metal to the molding installation.

[0188] In the example of [Fig. 10] the furnace installation 1010 includes a melting zone I equipped with immersion heaters 1016 and a magnetic stirring system 1013, a holding zone II, a metal treatment zone III equipped with a metal treatment system 1014, and a metal unloading zone IV equipped with the liquid metal dosing system 1015.

[0189] Advantageously, the fluidic connection 1033 between the furnace installation 1010 and the molding installation 1020 is short. Positioning the furnace installation 1010 in close proximity to the molding installation 1020, which consumes the liquid metal supplied by said furnace installation 1010, avoids the transport of liquid metal through a molding plant.

[0190] For example, if, according to the prior art, a large-capacity furnace supplies multiple molding machines, this necessitates the installation of a network of chutes to convey the molten metal from the furnace to each molding unit. This poses a safety problem and reduces the overall flexibility of the plant. In comparison, a foundry plant including a furnace installation according to the invention can be very easily adapted to a change in production volume or production schedule, by reducing the isothermal melting rate if the plant's flow rate needs to be decreased, by shutting down one of the furnace installations, or by using a furnace installation with a different alloy.

[0191] In such a foundry installation 1000 for the manufacture of molded parts according to the invention, the same furnace installation can supply a plurality of molding machines 1021.

[0192] A means of controlling the supply of solid metal to the furnace installation can be provided, which is controlled by a computer machine configured to use for this control information representing the consumption of liquid metal by said molding installation.

[0193] This foundry installation can be equipped with a conveyor that transports rejected castings from the molding unit to the furnace. These rejected castings are transported within range of the feeding means to supply solid metal to the solid metal melting zone, enabling the remelting of said rejected castings. In one embodiment, said conveyor can be a robot, which can be configured to grasp a rejected casting from the molding unit (possibly from a reject storage area located near the foundry machine) and place it onto the conveyor forming part of the furnace feeding means. Direct remelting of rejects from the molding unit in the furnace is possible because the rejected casting has the same alloy composition as the liquid metal contained in the furnace.

[0194] The furnace installation according to the invention can be manufactured in different sizes to suit a wide range of needs. Based on a dilution ratio of approximately 3, the following formats can be considered, for example:

[0195] (i) Furnace capacity of approximately 750 kg (corresponding to a melting capacity of approximately 250 kg / hour) for small molded parts production units, (ii) Furnace capacity of approximately 1,500 kg (melting capacity of approximately 500 kg / hour) for medium-sized molded parts production units, (iii) Furnace capacity of approximately 3,000 kg (melting capacity of approximately 500 kg / hour) for molded parts production units for the automotive sector, (iv) Furnace capacity of approximately 4,500 kg (melting capacity of approximately 1,500 kg / hour) for molded parts production units for the automotive sector, for casting raw shapes for processing or recycling, (v) Furnace capacity of approximately 9,000 kg (melting capacity of approximately 1,500 kg / hour) for large molded parts production units for the sector automotive, for casting raw forms for transformation or recycling,(vi) Furnace capacity of approximately 15,000 kg (melting capacity of approximately 5,000 kg / hour) for very large production units of molded parts for the automotive sector, for casting raw shapes for processing or recycling. Examples,

[0196] The applicant carried out several tests in a furnace installation according to the invention, which is shown schematically in [Fig. 17] and [Fig. 18]. Aluminum was used as the non-ferrous metal. This furnace installation has a holding capacity of approximately 1.3 tonnes of aluminum. As shown in [Fig. 18], the furnace melting zone was initially preheated using three radiant heating elements arranged horizontally near the furnace floor. In an adjacent area, three thermocouples were installed for the purposes of this example ([Fig. 18] shows only one thermocouple): thermocouple TC1Z1 at 50 mm from the bottom of the melting zone, thermocouple TC2Z1 at 100 mm from the bottom of the melting zone, and thermocouple TC3Z1 at 150 mm from the bottom of the melting zone.

[0197] Next, the superstructure containing the radiant heating elements was removed and replaced with immersion heaters and a magnetic stirring system in the melting zone, and a mechanical circulation pump in the adjacent zone; this can be seen in [Fig. 17]. The tests were carried out with a bath of approximately 750 kg to 800 kg of liquid metal in the enclosure (of which approximately 500 kg was in the melting zone).

[0198] Example 1:

[0199] Aluminum ingots (99.8%) were melted in the melting zone, following a procedure similar to that described in WO 2023 / 199257 A1. Batches of aluminum ingots, each with a unit mass of 5.2 kg, were then added, and the temperature of the metal in the melting zone was monitored using thermocouples. The temperature was recorded over time; this recording is shown in [Fig. 19], which shows three periods, labeled A, B, and C.

[0200] During period A, ten batches of a single ingot were added one after the other, for a total of 52 kg. During period B, two batches of four ingots each were added one after the other, for a total of 2 x 4 x 5.2 kg = 41.6 kg. During period C, five batches of three ingots each were added one after the other, for a total of 5 x 3 x 5.2 kg = 78 kg. This corresponded to a total addition of 33 ingots in approximately 61 minutes. It can be observed that for the introduction of a batch of one ingot, the temperature in the melting zone is within a range of approximately 3 °C.

[0201] Example 2:

[0202] Aluminum ingots, each weighing 5.2 kg, were introduced into the molten metal bath over a period of approximately 60 minutes. The total mass of aluminum varied between 147 kg and 177 kg. The electrical power was 58 kW, and the energy consumption was between approximately 327 and 340 kWh per ton of metal. Different operating methods were compared. Without stirring, a temperature difference of approximately 20 °C was observed in the melting zone, with a thermocouple deviation of approximately 10 °C. With stirring by a mechanical circulation pump installed in the holding zone, a temperature difference of approximately 7 °C was observed in the melting zone, with a thermocouple deviation of approximately 0.5 °C to 3 °C. With a magnetic stirring system installed at the bottom of the melting zone, a temperature difference of approximately 3°C was observed in the melting zone, with a difference per thermocouple of less than 1°C.This test demonstrates that the installation according to the invention, with a magnetic stirring system and a plurality of immersion heaters in the melting zone, is capable of maintaining isothermal conditions when batches of solid metal are regularly introduced into the melting zone. This makes the installation according to the invention suitable for continuous use to supply an external consumer also operating continuously.

Claims

DEMANDS 1. Furnace installation (1, 100, 200, 300, 500, 700, 1000) for non-ferrous metals, in particular aluminium, magnesium, zinc, tin, lead, comprising at least one enclosure (201, 202, 302, 42, 502, 602, 702, 1011) capable of containing liquid metal, and - at least two zones for liquid metal in fluidic connection, as well as - heating means which are solely electric, and which include at least one immersion heater (7,107,307,407,507,607,707,1016) for heating the molten metal and possibly at least one radiant heat source (2018,718) for preheating the furnace, - magnetic means for stirring (8,108,208,608,708,1013) the liquid metal, comprising at least one rotating permanent magnet (84,85), said magnetic stirring means being disposed in said enclosure and / or below said enclosure and / or on the side of said enclosure.

2. Non-ferrous metal furnace installation according to claim 1, characterized in that it comprises a first zone (572) for melting solid metal and a second zone (573) for holding liquid metal, or a first zone (572) for melting solid metal and a second zone (574) for processing liquid metal.

3. Furnace installation for non-ferrous metals according to claim 1 or 2, characterized in that it comprises a first zone (572) for melting solid metal, a second zone (573) for holding liquid metal, and a third zone (574) for processing liquid metal, and possibly a fourth zone (576) for unloading liquid metal.

4. Furnace installation for non-ferrous metals according to any one of claims 2 to 3, characterized in that it comprises at least one immersion heater (7,107,307,407,507,607,707,1016) located in said zone (572) for the melting of solid metal, and possibly at least one immersion heater in said holding zone (573) and / or in said zone (574) for the processing of liquid metal.

5. Furnace installation for non-ferrous metals according to any one of claims 2 to 4, characterized in that said magnetic stirring means (8,108,208,608,708,1013) are located in the melting zone (572).

6. Furnace installation for non-ferrous metals according to any one of claims 1 to 5, characterized in that said zones are delimited, within the same enclosure, by at least one wall comprising an opening (6,106,406,606), and / or correspond to two enclosures in fluidic connection.

7. Furnace installation for non-ferrous metals according to any one of claims 1 to 6, characterized in that it comprises at least two chambers in fluidic connection.

8. Furnace installation for non-ferrous metals according to any one of claims 1 to 7, characterized in that it comprises at least two enclosures in fluidic connection, and in that each zone corresponds to one enclosure.

9. Non-ferrous metal furnace installation according to any one of claims 1 to 8, characterized in that it comprises feeding means for supplying solid metal to said solid metal melting zone, said feeding means being able to comprise a conveyor and / or a vibrating hopper connected to a conveyor.

10. Furnace installation for non-ferrous metals according to claim 9, characterized in that said feeding means comprise an electric preheating means for drying said solid metal.

11. Furnace installation for non-ferrous metals according to claim 9 or 10, characterized in that said feeding means comprise a floor for presenting the solid metal at the edge of the melting zone, optionally provided with a mechanical pushing means for transferring the solid metal presented on said floor into said melting zone.

12. Furnace installation for non-ferrous metals according to any one of claims 9 to 11, characterized in that said feeding means comprise a robot configured to depalletize a pallet of solid metal ingots.

13. Furnace installation for non-ferrous metals according to any one of claims 1 to 12, characterized in that it comprises a zone for the melting of solid metal provided with a magnetic stirring means (8,108,208,608,708,1013) designed to be capable of generating a vortex which keeps solid metal chips submerged during their melting.

14. Furnace installation for non-ferrous metals according to any one of claims 1 to 13, characterized in that said installation comprises at least one movable wall to delimit an area.

15. Furnace installation for non-ferrous metals according to any one of claims 1 to 14, characterized in that at least one of said chambers capable of containing liquid metal includes at least one closable opening to be able to establish, if necessary, a new fluidic connection with another chamber capable of containing liquid metal or to remove liquid metal from said chamber.

16. Non-ferrous metal furnace installation according to any one of claims 1 to 15, characterized in that said installation comprises a metal outlet zone which includes at least one means for exiting liquid metal from said furnace installation.

17. Furnace installation for non-ferrous metals according to any one of claims 1 to 16, characterized in that said installation comprises a so-called dosing zone, provided with a device for taking a controlled quantity of liquid metal.

18. A method for melting non-ferrous metals in a furnace installation for ferrous metals according to any one of claims 1 to 17, wherein at least one of said immersion heaters (7, 107, 307, 407, 507, 607, 707, 1016) is regulated in the melting zone so that said installation can supply liquid metal to an external consumer while said melting zone is being fed with solid metal, and preferably at least one of said immersion heaters in the melting zone (572) is regulated so that the temperature of the liquid metal in the melting zone remains within a range whose width does not exceed 40 °C, preferably not exceed 25 °C, more preferably not exceed 15 °C, and even more preferably not exceed 10 °C.

19. A process according to claim 18, wherein the melting process is conducted so that the temperature of the liquid metal in the melting zone differs from that of the holding zone by more than 10 °C, and possibly by more than 20 °C.

20. Method according to claim 18 or 19, wherein at least one of said magnetic stirring means is also regulated.

21. Melting process according to any one of claims 18 to 20, characterized in that the melting process is operated in such a way that the mass ratio between the quantity of solid metal introduced into the melting zone and the quantity of liquid metal present in the melting zone is less than 6, preferably less than 5, even more preferably between 2.5 and 4.5, and optimally between 2.7 and 4.

0.

22. A melting process according to any one of claims 18 to 21, characterized in that said external consumer is a molding machine, preferably a die-casting machine comprising a permanent mold.

23. Foundry installation (1000) for the manufacture of castings using at least one mold, comprising a furnace installation for non-ferrous metals (1, 100, 200, 300, 500, 700, 1010) according to any one of claims 1 to 17, and further comprising at least one molding installation (1020) which is supplied by said furnace installation via a fluidic link (1030), said fluidic link preferably having a length of less than ten meters, more preferably less than five meters, even more preferably less than three meters, and even more preferably less than two meters, this length being measured from the outlet of the enclosure of said furnace installation to the inlet of said molding installation.

24. Foundry installation according to claim 23, comprising a means of transport, such as a robot, configured to transport rejected castings from the molding installation to the furnace installation, preferably within the range of said feeding means to supply solid metal to the solid metal melting zone, to enable the remelting of said rejected castings.

25. A method of operating a foundry installation according to claim 23 or 24, wherein said molding installation (1020) is operated to manufacture castings while the melting zone of said furnace installation (1010) is fed with solid metal, and preferably by operating a melting process according to any one of claims 18 to 22.

26. A method of operation according to claim 25, wherein said molding installation is supplied with liquid metal from said furnace installation by a means selected from the group consisting of: (i) a scooping ladle, (ii) an automatic dosing system, and in particular an automatic dosing system whose lower part is immersed in the bath and which allows a controlled quantity of liquid metal to be taken and introduced directly into the mold or into the injection chamber of the piston of the injection molding machine, (iii) a dosing pump, part of which is permanently immersed in the bath and which allows a controlled quantity of liquid metal to be introduced directly into the injection chamber of the injection molding machine piston, (iv) a liquid metal sampling system of the "dosing pipette" type connected to a mechanical arm enabling the filling of the piston chamber of the injection press.

27. A method of operation according to claim 25 or 26, wherein the method is operated in such a way that the mass ratio between the quantity of solid metal introduced into the melting zone and the quantity of liquid metal present in the melting zone is less than 6, preferably less than 5, even more preferably between 2.5 and 4.5, and optimally between 2.7 and 4.0.

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