EP1055354A1 - Method and induction furnace for melting a metallic or metal-containing bulk material in the shape of small pieces - Google Patents

Method and induction furnace for melting a metallic or metal-containing bulk material in the shape of small pieces

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Publication number
EP1055354A1
EP1055354A1 EP99908749A EP99908749A EP1055354A1 EP 1055354 A1 EP1055354 A1 EP 1055354A1 EP 99908749 A EP99908749 A EP 99908749A EP 99908749 A EP99908749 A EP 99908749A EP 1055354 A1 EP1055354 A1 EP 1055354A1
Authority
EP
European Patent Office
Prior art keywords
furnace
melt
induction
siphon
coil
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP99908749A
Other languages
German (de)
French (fr)
Other versions
EP1055354B1 (en
Inventor
Hans Bebber
Juan FÄHNRICH
Günter PHILLIPPS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Induga Industrieofen und Giesserei-Anlagen & Co KG GmbH
Original Assignee
Induga Industrieofen und Giesserei-Anlagen & Co KG GmbH
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Publication of EP1055354A1 publication Critical patent/EP1055354A1/en
Application granted granted Critical
Publication of EP1055354B1 publication Critical patent/EP1055354B1/en
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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
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/16—Furnaces having endless cores
    • H05B6/20—Furnaces having endless cores having melting channel only
    • 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
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/34—Arrangements for circulation of melts
    • 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
    • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
    • H05B2213/02—Stirring of melted material in melting furnaces

Definitions

  • the invention relates to a method and an induction furnace for melting small-sized metal and metal-containing bulk material, in particular in the form of chips made of iron, copper, copper alloys and / or aluminum and their alloys by means of inductive heating.
  • the induction crucible furnace which is mainly used for melting metal chips, in particular brass chips, consists of a refractory crucible, around which a water-cooled copper coil is arranged. If an alternating current flows through this coil, an alternating electromagnetic field is induced in the crucible insert, which causes the insert to melt. The resulting alternating field causes an intensive melt movement, which promotes the stirring in of the metal pieces placed in from above. By quickly stirring the abandoned, often oil-containing metal chips into the melt, metal losses of all kinds can be minimized and the formation of toxic hydrocarbons prevented.
  • the thermal efficiency of the crucible furnace is relatively low, which is why there is a high specific energy consumption. Furthermore, the crucible furnace can only be used batchwise. Once the maximum filling level of the crucible furnace has been reached, the melt must be poured before the further melting of metal pieces can continue. This creates non-productive times that considerably restrict the availability of the system.
  • An alternative is the so-called channel furnace, in which the melting material is in a closed channel around the iron core of a low-frequency transformer.
  • the melt forms the short-circuited secondary winding, the heating effect being created by the high current flowing in the melting channel.
  • the bath movement is missing in the channel furnace design, which increases the risk of metal burn-off as long as the metal pieces lying on the liquid bath are exposed to the oxidizing atmosphere.
  • the metal erosion can be counteracted to a limited extent by using rammers or agitators, which however increase the technical outlay.
  • the channel furnace Like the crucible furnace, the channel furnace only works discontinuously. In addition, it also has the disadvantage of high idle times. It is therefore an object of the present invention to improve the method and the induction furnace of the type mentioned at the outset by eliminating the aforementioned disadvantages. In particular, a continuous efficient melting of lumpy metal bulk goods and a suitable induction furnace that works with low maintenance are to be created.
  • the solution is that the metal bulk material is fed from above onto the melt produced in a furnace container and the upper region of the melt is exposed to a stirring movement by means of a first magnetic coil (crucible coil, stirring coil) arranged around the furnace container, wherein the melt is simultaneously supplied in the lower region in a melting channel around the iron core of a low-frequency transformer as a short-circuited secondary winding.
  • a first magnetic coil crucible coil, stirring coil
  • the method described has the advantage that a strong stirring movement is generated as a function of the frequency of the alternating voltage applied by means of a current-carrying crucible coil in order to avoid a metal fire and to minimize the amount of dross.
  • the melting channel in the area of which no more stirring work has to be carried out, can thus be optimally used with regard to its thermal efficiency. Overall, the method according to the invention can achieve significant energy savings of approximately 20%.
  • the melt is continuously discharged via a siphon with an opening located below the crucible coil and opening into the furnace container, preferably to the extent that metal piece goods are fed to the melt.
  • a constant molten bath surface level can be generated, which means that the slag zone is always in the same furnace wall area, so that an overgrowth of the furnace inner wall as in the crucible furnace or the cleaning work required therewith can be avoided.
  • the melting process can be carried out continuously with a stabilized process control.
  • there are no idle times as in the case of methods for temperature measurements and settings known from the prior art, which include slagging, emptying and cleaning. According to the invention, this results in an increase in production in the order of magnitude of approximately 30% and a reduction in operating costs of approximately 10%. Plant availability for production is significantly improved.
  • the method according to the invention creates the possibility of supplying more than 50%, preferably 60 to 70%, of the total electrical heating power supplied to produce the melt to the melting channel and the rest via the crucible coil, which increases the thermal efficiency through energy transfer into the Gutter is used.
  • the siphon can be heated if necessary.
  • the melt in the siphon is preferably discharged at an acute angle to the vertical or vertically according to the principle of the communicating tubes via an outlet of the siphon.
  • the siphon opening is arranged with respect to the channel inductor so that its heating and stirring movement extends into the melt flowing into the siphon opening.
  • the aforementioned measures allow the heat generated in the furnace area to be transported via the melt into the siphon, so that a siphon heater can be omitted to a corresponding extent.
  • the melt pool level will be set at the same height level as the siphon outlet opening. To the extent that metallic piece goods are melted down, melt also flows through the siphon outlet opening, for example into a casting installation.
  • the melt pool diameter defined by the furnace container is preferably chosen to be so large that the convex dross-free melt pool surface produced by the stirring movement is larger in diameter than twice the width of the scraper ring resting on the furnace edge.
  • the diameter of the so-called "bald head" in relation to the width of the scraper ring can be influenced via the frequency of the alternating field and the power which is fed to the crucible coil. Low frequencies in the area of the mains frequency have an advantageous effect here, since they promote the stirring effect.
  • the metal bulk material is fed exclusively onto the convex dross-free melt pool surface, in particular via a funnel.
  • the crucible coil is fed with an alternating current with a frequency of 50 to 250 Hz, preferably 50 to 120 Hz, and the channel inductor with an alternating current with a frequency of 50 to 60 Hz.
  • the object described at the outset is achieved by the induction furnace according to claim 10, which is characterized in that the furnace is designed to form a single melting chamber in the upper region as an induction crucible furnace and in the lower region as an induction channel furnace.
  • the induction furnace has a siphon that opens below the crucible coil of the induction crucible furnace part.
  • the siphon outlet runs vertically or at an acute angle to the vertical and has an outlet opening above the crucible coil. This measure avoids long flow paths which the liquid melt would otherwise have to cover from the furnace to the outflow. In addition, this arrangement allows heat convection and heat transport to be exploited via the melt in the furnace. Possibly.
  • the siphon is thermally insulated and / or can be heated by means of induction or resistance heating.
  • the siphon outflow diameter is preferably at least 150 mm.
  • the ratio of the induction coil height (stirring coil height) to the coil diameter is selected to be approximately 1: 2, positive and negative deviations of 20% being permissible.
  • the trough of the trough furnace part is arranged perpendicular to the siphon and the trough inductor is arranged horizontally.
  • inclined arrangements of the channel inductor or the channel are also conceivable, for example in order to support the flow movement of the melt in the direction of the siphon outlet.
  • the channel can also be arranged rotated through 90 ° relative to the siphon.
  • the induction furnace according to the invention has a single melting chamber 10, the upper area of which is surrounded by a water-cooled crucible coil 11.
  • the furnace itself has a fireproof lining 12 which is known in principle from the prior art.
  • a channel 13 is formed which can be heated by means of the channel inductor 14.
  • This channel inductor 14 consists of magnetic coils 15 above an iron core 16.
  • This structure results in an upper region 17, which corresponds to an induction crucible furnace, and a lower region 18, which corresponds to an induction channel furnace.
  • Below the crucible coil 11 but above the channel 13, the induction furnace has an outlet, namely the opening 19 of a siphon 20 opening into the furnace container, the longitudinal axis of which is inclined at an acute angle to the vertical.
  • the Siphon overflow opening 21 is located above crucible coil 11. From there, melt that flows away reaches a casting container 22 or the like.
  • the power supply lines for the crucible coil 11 and the channel inductor 14 are designated by 23.
  • the induction furnace according to the invention and the method according to the invention work as follows:
  • the metal shavings fed in via a funnel 24 or another pouring device reach the so-called bald head 25, which is the dross-free convex melt bath surface around which the so-called scraper ring 26 is located.
  • the metal chips task is directed such that metal chips fall on the bald head 25 without exception.
  • the crucible coil which is fed at a frequency between 50 Hz and 120 Hz, sets the melt in a stirring movement, by means of which the chips or pieces of metal lying on the bald head 25 are carried along and drawn into the melt. The melting of the small-sized metal particles thus takes place essentially in the melt, whereby metal burn-off can be prevented.
  • the heating power supplied to the entire induction furnace is supplied via the crucible coil 11, two thirds of this heating power is emitted via the channel inductor 14.
  • a melt column corresponding to the melt bath surface 25 is formed in the siphon 20. If the induction furnace is "filled” as shown, any further melt inflow produced by adding metal chips leads to an outflow of relevant quantities via the overflow 21.
  • the control of the process is designed so that the heating power is large enough to completely melt the introduced metal chips.
  • Processable chips consist in particular of iron, copper, aluminum and their alloys.
  • the method according to the invention can also be applied to metal-containing bulk goods that occur during the recycling of residues such as ashes, filter dusts, etc.
  • the induction furnace had an output of 2 MW, 1100 kW being emitted via the channel and 900 kW via the crucible coil 11. With appropriate furnace dimensions, 8 t / h brass chips could be melted down. The energy saved compared to a crucible furnace was about 20%.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Furnace Details (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • General Induction Heating (AREA)

Abstract

The present invention relates to a method as well as to an induction furnace for continuously melting a metallic or metal-containing bulk material in the shape of small pieces. The metallic bulk material is supplied from the top onto the melt located in the vessel of the furnace. An stirring movement is applied to the melt located in the upper area using an alternating field produced by a first magnetic coil (induction coil 11) which is arranged around the furnace vessel. Heat is simultaneously supplied to the melt, used as a short-circuited secondary winding, in the lower region of the induction-furnace crucible (13) about the iron core (16) of a low-frequency transformer.

Description

Beschreibung description
Verfahren und Induktionsofen zum Schmelzen von kleinstückigem Metall- und/oder metallhaltigem SchüttgutProcess and induction furnace for melting small-sized metal and / or metal-containing bulk goods
Die Erfindung betrifft ein Verfahren und einen Induktionsofen zum Schmelzen von kleinstückigem Metall- und metallhaltigem Schüttgut, insbesondere in Form von Spänen aus Eisen, Kupfer, Kupferlegierungen und/oder Aluminium und dessen Legierungen mittels induktiver Erwärmung.The invention relates to a method and an induction furnace for melting small-sized metal and metal-containing bulk material, in particular in the form of chips made of iron, copper, copper alloys and / or aluminum and their alloys by means of inductive heating.
Zum Schmelzen von kleinstückigem Metall- und/oder metallhaltigem Schüttgut, insbesondere von Spänen, wie sie bei der Metall- Zerspanung anfallen, sind nach dem Stand der Technik zwei unterschiedliche Induktionsofen-Typen bekannt. Beide Ofentypen basieren auf der Ausnutzung der magnetischen Induktion.Two different types of induction furnace are known in the prior art for melting small-sized metal and / or metal-containing bulk material, in particular chips, such as are produced in metal cutting. Both types of furnace are based on the use of magnetic induction.
Der vorwiegend zum Einschmelzen von Metallspänen, insbesondere Messingspänen, eingesetzte Induktionstiegelofen besteht aus einem feuerfesten Tiegel, um den eine wassergekühlte Kupferspule angeordnet ist. Wird diese Spule von einem Wechselstrom durchflössen, so wird in dem Tiegeleinsatz ein elektromagnetisches Wechselfeld induziert, das den Einsatz zum Schmelzen bringt. Das hierbei entstehende Wechselfeld bewirkt eine intensive Schmelzebewegung, welche das Einrühren der von oben aufgegebenen Metallstücke fördert. Dadurch, daß die aufgegebenen, oft ölhaltigen Metallspäne rasch in die Schmelze eingerührt werden, lassen sich Metallverluste jeder Art minimieren und die Bildung von toxischen Kohlenwasserstoffen verhindern.The induction crucible furnace, which is mainly used for melting metal chips, in particular brass chips, consists of a refractory crucible, around which a water-cooled copper coil is arranged. If an alternating current flows through this coil, an alternating electromagnetic field is induced in the crucible insert, which causes the insert to melt. The resulting alternating field causes an intensive melt movement, which promotes the stirring in of the metal pieces placed in from above. By quickly stirring the abandoned, often oil-containing metal chips into the melt, metal losses of all kinds can be minimized and the formation of toxic hydrocarbons prevented.
Die Ströme in der Magnetspule und im Schmelzgut erzeugen zusammen mit dem Magnetfeld Kräfte in Richtung auf die Zylinderachse, wodurch sich eine konvexe Schmelzbadoberfläche ausbildet. Ringförmig um die Schmelzbadoberfläche setzt sich am Ofeninnenmantel Krätze ab, wobei die Breite des Krätze-Ringes um so geringer ist, je heftiger die Badbewegung ist. Der geschilderte Tiegelofen hat verfahrensbedingt folgende Nachteile:The currents in the magnetic coil and in the melting material, together with the magnetic field, generate forces in the direction of the cylinder axis, as a result of which a convex molten pool surface is formed. Scabies are deposited in a ring around the surface of the molten bath on the furnace inner jacket, the width of the scabies ring being smaller the more violent the bath movement is. The crucible furnace described has the following disadvantages due to the process:
Zunächst ist der thermische Wirkungsgrad des Tiegelofens relativ gering, weshalb sich ein hoher spezifischer Energieverbrauch ergibt. Des weiteren kann mit dem Tiegelofen nur diskontinuierlich gearbeitet werden. Ist der maximale Füllgrad des Tiegelofens erreicht, muß die Schmelze vergossen werden, bevor mit dem weiteren Einschmelzen von Metallstücken fortgefahren werden kann. Hierdurch entstehen Nebenzeiten, die die Anlagenverfügbarkeit erheblich einschränken.First of all, the thermal efficiency of the crucible furnace is relatively low, which is why there is a high specific energy consumption. Furthermore, the crucible furnace can only be used batchwise. Once the maximum filling level of the crucible furnace has been reached, the melt must be poured before the further melting of metal pieces can continue. This creates non-productive times that considerably restrict the availability of the system.
Durch Ablagerungen an der Tiegelwand ergibt sich ein hoher Reinigungsaufwand. Schließlich führen Schlackenanhaftungen an der Tiegelwand zu nicht unerheblichen Leistungsverlusten.Deposits on the crucible wall result in a high level of cleaning effort. Finally, slag build-up on the crucible wall leads to considerable performance losses.
Eine Alternative bietet der sogenannte Rinnenofen, bei dem sich das Schmelzgut in einer geschlossenen Rinne um den Eisenkern eines Niederfrequenztransformators befindet. Die Schmelze bildet die kurzgeschlossene Sekundärwicklung, wobei die Heizwirkung durch den hohen, in der Schmelzrinne fließenden Strom entsteht. Allerdings fehlt bei der Rinnenofen-Ausführung die Badbewegung, wodurch die Gefahr des Metallabbrandes erhöht ist, soweit die auf dem flüssigen Bad liegenden Metallstücke der oxidierenden Atmosphäre ausgesetzt sind. Bedingt kann dem Metallabbrand durch Einsatz von Stampfern oder Rührwerken entgegengewirkt werden, die jedoch den technischen Aufwand erhöhen. Obwohl der thermische Wirkungsgrad des Rinnenofens groß ist, können nur kleine Schmelzleistungen erzielt werden, da das mechanische Einrühren zeitintensiv ist. Im Regelfall werden nur 30 % Metallspan-Anteile zum stückigen Schrott zugesetzt, um befriedigende Schmelzleistungen zu erzielen. Ebenso wie der Tiegelofen arbeitet der Rinnenofen nur diskontinuierlich. Außerdem ist auch er mit dem Nachteil hoher Nebenzeiten behaftet. Es ist daher Aufgabe der vorliegenden Erfindung, das Verfahren und den Induktionsofen der eingangs genannten Art zu verbessern, indem die vorgenannten Nachteile beseitigt werden. Insbesondere soll ein kontinuierliches effizientes Einschmelzen von stückigem Metall-Schüttgut und ein hierzu geeigneter Induktionsofen geschaffen werden, der wartungsarm arbeitet.An alternative is the so-called channel furnace, in which the melting material is in a closed channel around the iron core of a low-frequency transformer. The melt forms the short-circuited secondary winding, the heating effect being created by the high current flowing in the melting channel. However, the bath movement is missing in the channel furnace design, which increases the risk of metal burn-off as long as the metal pieces lying on the liquid bath are exposed to the oxidizing atmosphere. The metal erosion can be counteracted to a limited extent by using rammers or agitators, which however increase the technical outlay. Even though the thermal efficiency of the channel furnace is high, only low melting rates can be achieved because the mechanical stirring is time-consuming. As a rule, only 30% metal chips are added to the lumpy scrap in order to achieve satisfactory melting performance. Like the crucible furnace, the channel furnace only works discontinuously. In addition, it also has the disadvantage of high idle times. It is therefore an object of the present invention to improve the method and the induction furnace of the type mentioned at the outset by eliminating the aforementioned disadvantages. In particular, a continuous efficient melting of lumpy metal bulk goods and a suitable induction furnace that works with low maintenance are to be created.
Verfahrenstechnisch besteht die Lösung darin, daß auf die in einem Ofenbehälter erzeugte Schmelze das Metall-Schüttgut von oben zugeführt wird und die Schmelze im oberen Bereich durch ein mittels einer ersten um den Ofenbehälter angeordneten Magnetspule (Tiegelspule, Rührspule) erzeugtes Wechselfeld einer Rührbewegung ausgesetzt wird, wobei der Schmelze gleichzeitig im unteren Bereich in einer Schmelzrinne um den Eisenkern eines Niederfrequenztransformators als kurzgeschlossene Sekundärwicklung Wärme zugeführt wird. Das beschriebene Verfahren hat den Vorteil, daß mittels einer stromdurchflossenen Tiegelspule in Abhängigkeit der Frequenz der aufgegebenen Wechselspannung eine starke Rührbewegung zur Vermeidung eines Metallbrandes und zur Minimierung der Krätzemenge erzeugt wird. Die Schmelzrinne, in deren Bereich keine Rührarbeit mehr geleistet werden muß, läßt sich so hinsichtlich ihres thermischen Wirkungsgrades optimal ausnutzen. Insgesamt läßt sich durch das erfindungsgemäße Verfahren eine deutliche Energieersparnis von ca. 20 % erzielen.In terms of process technology, the solution is that the metal bulk material is fed from above onto the melt produced in a furnace container and the upper region of the melt is exposed to a stirring movement by means of a first magnetic coil (crucible coil, stirring coil) arranged around the furnace container, wherein the melt is simultaneously supplied in the lower region in a melting channel around the iron core of a low-frequency transformer as a short-circuited secondary winding. The method described has the advantage that a strong stirring movement is generated as a function of the frequency of the alternating voltage applied by means of a current-carrying crucible coil in order to avoid a metal fire and to minimize the amount of dross. The melting channel, in the area of which no more stirring work has to be carried out, can thus be optimally used with regard to its thermal efficiency. Overall, the method according to the invention can achieve significant energy savings of approximately 20%.
Nach einer Weiterbildung des erfindungsgemäßen Verfahrens wird die Schmelze über einen Siphon mit einer unterhalb der Tiegelspule liegenden, in den Ofenbehälter mündenden Öffnung kontinuierlich abgeführt, vorzugsweise in dem Maß, wie Metallstückgut der Schmelze zugeführt wird. Mit dieser Maßnahme kann ein konstantes Schmelzbadoberflächeniveau erzeugt werden, wodurch bewirkt wird, daß die Schlackezone stets im gleichen Ofenwandbereich liegt, so daß ein Zuwachsen der Ofeninnenwand wie beim Tiegelofen bzw. die damit erforderlichen Reinigungsarbeiten vermieden werden können. Der Einschmelzprozeß kann kontinuierlich bei einer stabilisierten Prozeßführung vorgenommen werden. Vorteilhafterweise entstehen keine Nebenzeiten wie bei nach dem Stand der Technik bekannten Verfahren für Temperaturmessungen und -einstellungen, das Abschlacken, Entleeren und Reinigen aufzuwenden sind. Hierdurch ergibt sich erfindungsgemäß eine Produktionserhöhung in der Größenordnung von ca. 30 % sowie eine Betriebskostensenkung von ca. 10 %. Die Anlagenverfügbarkeit für die Produktion wird erheblich verbessert.According to a development of the method according to the invention, the melt is continuously discharged via a siphon with an opening located below the crucible coil and opening into the furnace container, preferably to the extent that metal piece goods are fed to the melt. With this measure, a constant molten bath surface level can be generated, which means that the slag zone is always in the same furnace wall area, so that an overgrowth of the furnace inner wall as in the crucible furnace or the cleaning work required therewith can be avoided. The melting process can be carried out continuously with a stabilized process control. Advantageously, there are no idle times, as in the case of methods for temperature measurements and settings known from the prior art, which include slagging, emptying and cleaning. According to the invention, this results in an increase in production in the order of magnitude of approximately 30% and a reduction in operating costs of approximately 10%. Plant availability for production is significantly improved.
Wie bereits erwähnt, schafft das erfindungsgemäße Verfahren die Möglichkeit, mehr als 50 %, vorzugsweise 60 bis 70 %, der gesamten zur Erzeugung der Schmelze zugeführten elektrischen Heizleistung der Schmelzrinne und den Rest über die Tiegelspule zuzuführen, womit der höhere thermische Wirkungsgrad durch Energieübertragung in die Rinne ausgenutzt wird.As already mentioned, the method according to the invention creates the possibility of supplying more than 50%, preferably 60 to 70%, of the total electrical heating power supplied to produce the melt to the melting channel and the rest via the crucible coil, which increases the thermal efficiency through energy transfer into the Gutter is used.
Je nach Ausbildung des Siphons kann dieser ggf. beheizt werden.Depending on the design of the siphon, it can be heated if necessary.
Vorzugsweise wird die Schmelze im Siphon spitzwinklig zur Senkrechten oder senkrecht nach dem Prinzip der kommunizierenden Röhren über einen Auslauf des Siphons abgeführt. Hierbei wird nach einer Weiterbildung des Verfahrens die Siphonmündungsöffnung in bezug auf den Rinneninduktor so angeordnet, daß dessen Heiz- und Rührbewegung bis in die in die Siphonmündungsöffnung fließende Schmelze hineinreicht. Die vorgenannten Maßnahmen erlauben es, daß die im Ofenbereich erzeugte Wärme über die Schmelze in den Siphon transportiert wird, so daß in entsprechendem Maße eine Siphon-Heizung unterbleiben kann. In dem verwendeten Ofengefäß wird sich der Schmelzbadspiegel in demselben Höhenniveau einstellen, in dem sich die Siphonauslaßöffnung befindet. In dem Maße, in dem metallisches Stückgut eingeschmolzen wird, fließt auch Schmelze über die Siphonauslaßöffnung, etwa in eine Gießanlage, ab. Bei einer solchen kontinuierlichen Verfahrensführung ist auch kein Reinigen der Ofen- Innenwand erforderlich, so daß diesbezügliche Ofenstillstandszeiten entfallen. Vorzugsweise wird der durch den Ofenbehälter definierte Schmelzbaddurchmesser so groß gewählt, daß die durch die Rührbewegung erzeugte konvexe krätzefreie Schmelzbadoberfläche im Durchmesser größer ist als die doppelte Breite des am Ofenrand anliegenden Krätzeringes. Der Durchmesser der sogenannten "Glatze" im Verhältnis zur Krätzeringbreite läßt sich über die Frequenz des Wechselfeldes und die Leistung beeinflussen, welche der Tiegelspule zugeführt wird. Niedrige Frequenzen im Bereich der Netzfrequenz wirken sich hierbei vorteilhaft aus, da sie die Rührwirkung fördern. Zur Vermeidung von Metallabbrand wird das aufgegebene metallische Schüttgut ausschließlich auf die konvexe krätzefreie Schmelzbadoberfläche, insbesondere über einen Trichter zugeführt.The melt in the siphon is preferably discharged at an acute angle to the vertical or vertically according to the principle of the communicating tubes via an outlet of the siphon. Here, according to a development of the method, the siphon opening is arranged with respect to the channel inductor so that its heating and stirring movement extends into the melt flowing into the siphon opening. The aforementioned measures allow the heat generated in the furnace area to be transported via the melt into the siphon, so that a siphon heater can be omitted to a corresponding extent. In the furnace vessel used, the melt pool level will be set at the same height level as the siphon outlet opening. To the extent that metallic piece goods are melted down, melt also flows through the siphon outlet opening, for example into a casting installation. With such a continuous process, no cleaning of the inner wall of the furnace is necessary, so that the relevant furnace downtimes are eliminated. The melt pool diameter defined by the furnace container is preferably chosen to be so large that the convex dross-free melt pool surface produced by the stirring movement is larger in diameter than twice the width of the scraper ring resting on the furnace edge. The diameter of the so-called "bald head" in relation to the width of the scraper ring can be influenced via the frequency of the alternating field and the power which is fed to the crucible coil. Low frequencies in the area of the mains frequency have an advantageous effect here, since they promote the stirring effect. In order to avoid metal erosion, the metal bulk material is fed exclusively onto the convex dross-free melt pool surface, in particular via a funnel.
Nach einer besonderen Ausgestaltung der Erfindung werden die Tiegelspule mit einem Wechselstrom einer Frequenz von 50 bis 250 Hz, vorzugsweise 50 bis 120 Hz, und der Rinneninduktor mit einem Wechselstrom einer Frequenz von 50 bis 60 Hz gespeist.According to a special embodiment of the invention, the crucible coil is fed with an alternating current with a frequency of 50 to 250 Hz, preferably 50 to 120 Hz, and the channel inductor with an alternating current with a frequency of 50 to 60 Hz.
Apparativ wird die eingangs beschriebene Aufgabe durch den Induktionsofen nach Anspruch 10 gelöst, der dadurch gekennzeichnet ist, daß der Ofen unter Ausbildung einer einzigen Schmelzkammer im oberen Bereich als Induktionstiegelofen und im unteren Bereich als Induktionsrinnenofen ausgebildet ist.In terms of apparatus, the object described at the outset is achieved by the induction furnace according to claim 10, which is characterized in that the furnace is designed to form a single melting chamber in the upper region as an induction crucible furnace and in the lower region as an induction channel furnace.
Weitere vorzugsweise Ausbildungen des Induktionsofens sind in den Ansprüchen 11 bis 17 beschrieben.Further preferred designs of the induction furnace are described in claims 11 to 17.
So besitzt der Induktionsofen einen Siphon, der unterhalb der Tiegelspule des Induktions-Tiegelofenteiles mündet. Der Siphonausfluß verläuft vertikal oder spitzwinklig zur Vertikalen und besitzt eine Ausflußöffnung oberhalb der Tiegelspule. Durch diese Maßnahme werden lange Fließwege vermieden, welche die flüssige Schmelze ansonsten vom Ofen zu Ausfluß zurückzulegen hätte. Darüber hinaus läßt sich durch diese Anordnung die Wär- mekonvektion und der Wärmetransport über die im Ofen befindliche Schmelze ausnutzen. Ggf. ist der Siphon wärmeisoliert und/oder mittels einer Induk- tions- oder Widerstandsheizung erwärmbar. Bevorzugt beträgt der Siphonausflußdurchmesser mindestens 150 mm.For example, the induction furnace has a siphon that opens below the crucible coil of the induction crucible furnace part. The siphon outlet runs vertically or at an acute angle to the vertical and has an outlet opening above the crucible coil. This measure avoids long flow paths which the liquid melt would otherwise have to cover from the furnace to the outflow. In addition, this arrangement allows heat convection and heat transport to be exploited via the melt in the furnace. Possibly. the siphon is thermally insulated and / or can be heated by means of induction or resistance heating. The siphon outflow diameter is preferably at least 150 mm.
In einer weiteren Ausführungsform des Induktionsofens wird das Verhältnis der Induktionsspulenhöhe (Rührspulenhöhe) zum Spulendurchmesser etwa 1 : 2 gewählt, wobei positive wie negative Abweichungen um 20 % zulässig sind.In a further embodiment of the induction furnace, the ratio of the induction coil height (stirring coil height) to the coil diameter is selected to be approximately 1: 2, positive and negative deviations of 20% being permissible.
In einer ersten Ausführungsform des erfindungsgemäßen Induktionsofens ist die Rinne des Rinnenofenteiles senkrecht zum Siphon und der Rinneninduktor waagerecht angeordnet. Es sind jedoch auch Schräganordnungen des Rinneninduktors bzw. der Rinne denkbar, etwa um die Flußbewegung der Schmelze in Richtung des Siphon-Ausganges zu unterstützen. Selbstverständlich kann im Sinne der vorliegenden Erfindung die Rinne auch um 90° relativ zum Siphon gedreht angeordnet werden.In a first embodiment of the induction furnace according to the invention, the trough of the trough furnace part is arranged perpendicular to the siphon and the trough inductor is arranged horizontally. However, inclined arrangements of the channel inductor or the channel are also conceivable, for example in order to support the flow movement of the melt in the direction of the siphon outlet. Of course, in the sense of the present invention, the channel can also be arranged rotated through 90 ° relative to the siphon.
Ein Ausführungsbeispiel eines erfindungsgemäßen Induktionsofens ist in der Zeichnung dargestellt, die Querschnittsansicht dieses Induktionsofens zeigt.An embodiment of an induction furnace according to the invention is shown in the drawing, which shows a cross-sectional view of this induction furnace.
Der Erfindungsgemäße Induktionsofen besitzt eine einzige Schmelzkammer 10, deren oberer Bereich von einer wassergekühlten Tiegelspule 11 umgeben ist. Der Ofen selbst besitzt eine nach dem Stand der Technik im Prinzip bekannte feuerfeste Auskleidung 12. Im unteren Bereich des Ofens ist eine Rinne 13 ausgebildet, die mittels des Rinneninduktors 14 beheizbar ist. Dieser Rinneninduktor 14 besteht aus Magnetspulen 15 über einem Eisenkern 16. Durch diesen Aufbau ergibt sich ein oberer Bereich 17, der einem Induktionstiegelofen entspricht, sowie ein unterer Bereich 18, der einem Induktions-Rinnenofen entspricht. Unterhalb der Tiegelspule 11 aber oberhalb der Rinne 13 besitzt der Induktionsofen einen Auslaß, nämlich die in den Ofenbehälter mündende Öffnung 19 eines Siphons 20, dessen Längsachse spitzwinklig zur Vertikalen geneigt ist. Die Siphonüberlauföffnung 21 befindet sich oberhalb der Tiegelspule 11. Von dort aus gelangt abfließende Schmelze in einen Gießbehälter 22 oder ähnliches. Die Stromversorgungsleitungen für die Tiegelspule 11 sowie den Rinneninduktor 14 ist mit 23 bezeichnet. Der erfindungsgemäße Induktionsofen bzw. das erfindungsgemäße Verfahren arbeiten folgendermaßen:The induction furnace according to the invention has a single melting chamber 10, the upper area of which is surrounded by a water-cooled crucible coil 11. The furnace itself has a fireproof lining 12 which is known in principle from the prior art. In the lower region of the furnace a channel 13 is formed which can be heated by means of the channel inductor 14. This channel inductor 14 consists of magnetic coils 15 above an iron core 16. This structure results in an upper region 17, which corresponds to an induction crucible furnace, and a lower region 18, which corresponds to an induction channel furnace. Below the crucible coil 11 but above the channel 13, the induction furnace has an outlet, namely the opening 19 of a siphon 20 opening into the furnace container, the longitudinal axis of which is inclined at an acute angle to the vertical. The Siphon overflow opening 21 is located above crucible coil 11. From there, melt that flows away reaches a casting container 22 or the like. The power supply lines for the crucible coil 11 and the channel inductor 14 are designated by 23. The induction furnace according to the invention and the method according to the invention work as follows:
Die über einen Trichter 24 oder eine sonstige Schüttvorrichtung aufgegebenen Metallspäne gelangen auf die sogenannte Glatze 25, das ist die krätzefreie konvexe Schmelzbadoberfläche, um die herum der sogenannte Krätzering 26 ist. Die Metallspäneaufgabe ist derart gerichtet, daß Metallspäne ausnahmslos auf die Glatze 25 fallen. Durch die Tiegelspule, die mit einer Frequenz zwischen 50 Hz bis 120 Hz gespeist wird, wird die Schmelze in eine Rührbewegung versetzt, durch welche die auf der Glatze 25 aufliegenden Späne oder Metallstückchen mitgerissen und in die Schmelze gezogen werden. Das Aufschmelzen der kleinstückigen Metallteilchen geschieht somit im wesentlichen in der Schmelze, wodurch ein Metallabbrand verhindert werden kann. Vorzugsweise wird über die Tiegelspule 11 nur etwa ein Drittel der dem gesamten Induktionsofen zugeführten Heizleistung zugeführt, zwei Drittel dieser Heizleistung werden über den Rinneninduktor 14 abgegeben. Nach dem Prinzip der kommunizierenden Röhren bildet sich im Siphon 20 eine Schmelzesäule entsprechend der Schmelzbadoberfläche 25 aus. Ist der Induktionsofen, wie dargestellt, "gefüllt", führt jeder weitere durch Metallspänezugabe erzeugte Schmelzenzufluß zu einem Abfließen betreffender Mengen über den Überlauf 21. Die Steuerung des Verfahrens ist so angelegt, daß die Heizleistung groß genug ist, um die eingeführten Metallspäne vollständig aufzuschmelzen. Verarbeitbare Späne bestehen insbesondere aus Eisen, Kupfer, Aluminium und deren Legierungen. Das erfindungsgemäße Verfahren ist jedoch auch auf metallhaltige Schüttgüter anwendbar, die beim Recycling von Reststoffen wie Aschen, Filterstäube etc. auftreten. In einem konkreten Ausführungsbeispiel besaß der Induktionsofen eine Leistung von 2 MW, wobei 1100 kW über die Rinne und 900 kW über die Tiegelspule 11 abgegeben worden sind. Durch entsprechende Ofendimensionierung konnten 8 t/h Messingspäne eingeschmolzen werden. Die erzielte Energieeinsparung gegenüber einem Tiegelofen betrug etwa 20 %. The metal shavings fed in via a funnel 24 or another pouring device reach the so-called bald head 25, which is the dross-free convex melt bath surface around which the so-called scraper ring 26 is located. The metal chips task is directed such that metal chips fall on the bald head 25 without exception. The crucible coil, which is fed at a frequency between 50 Hz and 120 Hz, sets the melt in a stirring movement, by means of which the chips or pieces of metal lying on the bald head 25 are carried along and drawn into the melt. The melting of the small-sized metal particles thus takes place essentially in the melt, whereby metal burn-off can be prevented. Preferably, only about a third of the heating power supplied to the entire induction furnace is supplied via the crucible coil 11, two thirds of this heating power is emitted via the channel inductor 14. According to the principle of the communicating tubes, a melt column corresponding to the melt bath surface 25 is formed in the siphon 20. If the induction furnace is "filled" as shown, any further melt inflow produced by adding metal chips leads to an outflow of relevant quantities via the overflow 21. The control of the process is designed so that the heating power is large enough to completely melt the introduced metal chips. Processable chips consist in particular of iron, copper, aluminum and their alloys. However, the method according to the invention can also be applied to metal-containing bulk goods that occur during the recycling of residues such as ashes, filter dusts, etc. In a specific exemplary embodiment, the induction furnace had an output of 2 MW, 1100 kW being emitted via the channel and 900 kW via the crucible coil 11. With appropriate furnace dimensions, 8 t / h brass chips could be melted down. The energy saved compared to a crucible furnace was about 20%.

Claims

Patentansprüche claims
1. Verfahren zum Schmelzen von kleinstückigem Metall- und/oder metallhaltigem Schüttgut, insbesondere Spänen aus Eisen, Kupfer und/oder Aluminium, und/oder deren Legierungen mittels induktiver Erwärmung, d a d u r c h g e k e n n z e i c h n e t, daß auf die in einem Ofenbehälter erzeugte Schmelze das Metall-Schüttgut von oben zugeführt wird und die Schmelze im oberen Bereich durch ein mittels einer ersten um den Ofenbehälter angeordneten Magnetspule (Tiegelspule (11), Rührspule) erzeugtes Wechselfeld einer Rührbewegung ausgesetzt wird, wobei der Schmelze gleichzeitig im unteren Bereich in einer Schmelzrinne (13) um den Eisenkern (16) eines Niederfrequenz-Transformators als kurzgeschlossene Sekundärwicklung Wärme zugeführt wird.1. A method for melting small-sized metal and / or metal-containing bulk material, in particular chips made of iron, copper and / or aluminum, and / or their alloys by means of induction heating, characterized in that the metal bulk material of the melt produced in an oven container is supplied above and the melt in the upper region is exposed to a stirring movement by means of an alternating field generated by means of a first magnetic coil (crucible coil (11), stirring coil) arranged around the furnace container, the melt simultaneously in the lower region in a melting channel (13) around the iron core (16) a low-frequency transformer as short-circuited secondary winding heat is supplied.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Schmelze über einen Siphon (20) mit einer unterhalb der Tiegelspule (11) liegenden, in den Ofenbehälter mündenden Öffnung (19) kontinuierlich in dem Maß abgeführt wird wie Metallstückgut der Schmelze zugeführt wird.2. The method according to claim 1, characterized in that the melt is continuously discharged via a siphon (20) with a below the crucible coil (11), opening into the furnace container opening (19) to the extent that metal piece goods are fed to the melt.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß mehr als 50 %, vorzugsweise 60 bis 70 %, der gesamten zur Erzeugung der Schmelze zugeführten elektrischen Heizleistung der Schmelzrinne (13) und der Rest über die Tiegelspule (11) zugeführt werden.3. The method according to claim 1 or 2, characterized in that more than 50%, preferably 60 to 70%, of the total electrical heating power supplied to produce the melt of the melting channel (13) and the rest are supplied via the crucible coil (11).
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der Siphon (20) beheizt wird, vorzugsweise mittels einer Induktions- oder Widerstandsheizung.4. The method according to any one of claims 1 to 3, characterized in that the siphon (20) is heated, preferably by means of an induction or resistance heating.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Schmelze im Siphon (20) spitzwinklig zur Senkrechten oder senkrecht nach dem Prinzip der 105. The method according to any one of claims 1 to 4, characterized in that the melt in the siphon (20) at an acute angle to the vertical or perpendicular according to the principle of 10
kommunizierenden Röhren über einen Auslauf (21) des Siphons (20) kontinuierlich abgeführt wird.communicating tubes is continuously discharged via an outlet (21) of the siphon (20).
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß die Siphonmündungsöffnung (19) in bezug auf die Tiegelspule (11) so angeordnet ist, daß die Rührbewegung bis in die Siphonmündungsöffnung (19) fließende Schmelze hineinreicht .6. The method according to claim 5, characterized in that the siphon opening (19) with respect to the crucible coil (11) is arranged so that the stirring movement extends into the siphon opening (19) flowing melt.
7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß der durch den Ofenbehälter definierte Schmelzbaddurchmesser (d) so groß gewählt wird, daß die durch die Rührbewegung erzeugte konvexe (krätzefreie) Schmelzbadoberfläche (25) im Durchmesser größer als die zweifache Breite des am Ofenrand anliegenden Ringes der Krätze (26) ist.7. The method according to any one of claims 1 to 6, characterized in that the melt pool diameter (d) defined by the furnace container is chosen so large that the convex (dross-free) melt pool surface (25) produced by the stirring movement has a diameter greater than twice the width of the ring of dross (26) adjacent to the edge of the furnace.
8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß das Metall-Schüttgut ausschließlich auf die konvexe krätzefreie Schmelzbadoberfläche (25) aufgegeben wird, vorzugsweise zentrisch über einen Schüttgut-Trichter.8. The method according to claim 7, characterized in that the metal bulk material is applied exclusively to the convex dross-free melt pool surface (25), preferably centrally via a bulk material hopper.
9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß die Tiegelspule (11) mit einem Wechselstrom einer Frequenz von 50 bis 250 Hz, vorzugsweise 50 bis 120 Hz, und der Rinneninduktor (14) mit einem Wechselstrom einer Frequenz von 50 bis 60 Hz gespeist werden.9. The method according to any one of claims 1 to 8, characterized in that the crucible coil (11) with an alternating current of a frequency of 50 to 250 Hz, preferably 50 to 120 Hz, and the channel inductor (14) with an alternating current of a frequency of 50 up to 60 Hz.
10. Induktionsofen zum kontinuierlichen Schmelzen von klein stückigem Metall- und/oder metallhaltigem Schüttgut, insbesondere in Form von Spänen aus Eisen, Kupfer und/oder Aluminium und deren Legierungen, dadurch gekennzeichnet, daß der Ofen unter Ausbildung einer einzigen Schmelzkammer (10) im oberen Bereich (17) als Induktionstiegelofen und im unteren Bereich (18) als Induktionsrinnenofen ausgebildet ist. 1110. Induction furnace for the continuous melting of small-piece metal and / or metal-containing bulk material, in particular in the form of chips made of iron, copper and / or aluminum and their alloys, characterized in that the furnace with formation of a single melting chamber (10) in the upper Area (17) is designed as an induction crucible oven and in the lower area (18) as an induction channel oven. 11
11. Induktionsofen nach Anspruch 10, gekennzeichnet durch einen Siphon (20), der unterhalb der Tiegelspule (11) des Induktionstiegelofenteiles (17) mündet.11. Induction furnace according to claim 10, characterized by a siphon (20) which opens below the crucible coil (11) of the induction crucible furnace part (17).
12. Induktionsofen nach Anspruch 11, dadurch gekennzeichnet, daß der Siphonausfluß (20) vertikal oder spitzwinklig zur Vertikalen verläuft und seine Ausflußöffnung (21) oberhalb der Tiegelspule (11) besitzt.12. Induction furnace according to claim 11, characterized in that the siphon outlet (20) extends vertically or at an acute angle to the vertical and has its outlet opening (21) above the crucible coil (11).
13. Induktionsofen nach Anspruch 12, dadurch gekennzeichnet, daß der Siphon (20) wärmeisoliert ist und/oder mittels einer Induktions- oder Widerstandsheizung erwärmbar ist.13. Induction furnace according to claim 12, characterized in that the siphon (20) is thermally insulated and / or can be heated by means of an induction or resistance heater.
14. Induktionsofen nach einem der Ansprüche 12 oder 13, dadurch gekennzeichnet, daß der Siphonausflußdurchmesser mindestens 150 mm beträgt.14. Induction furnace according to one of claims 12 or 13, characterized in that the siphon outflow diameter is at least 150 mm.
15. Induktionsofen nach einem der Ansprüche 10 bis 14, dadurch gekennzeichnet, daß das Verhältnis der Rührspulenhöhe zum Rührspulendurchmesser 1 : 2 (± 20 %) beträgt.15. Induction furnace according to one of claims 10 to 14, characterized in that the ratio of the stirring coil height to the stirring coil diameter is 1: 2 (± 20%).
16. Induktionsofen nach einem der Ansprüche 1 bis 15, dadurch gekennzeichnet, daß die Rinne (13) des Rinnenofentei- les (18) senkrecht zum Siphon (20) angeordnet ist.16. Induction furnace according to one of claims 1 to 15, characterized in that the channel (13) of the channel furnace part (18) is arranged perpendicular to the siphon (20).
17. Induktionsofen nach einem der Ansprüche 10 bis 16, dadurch gekennzeichnet, daß der Rinneninduktor (14) waagerecht oder schräg zur Siphonachse angeordnet ist.17. Induction furnace according to one of claims 10 to 16, characterized in that the channel inductor (14) is arranged horizontally or obliquely to the siphon axis.
18. Induktionsofen nach einem der Ansprüche 10 bislδ, dadurch gekennzeichnet, daß der Rinneninduktor (14) um 90° zur Senkrechten verdreht angeordnet ist. 18. Induction furnace according to one of claims 10 bislδ, characterized in that the channel inductor (14) is arranged rotated by 90 ° to the vertical.
EP99908749A 1998-02-12 1999-01-22 Method and induction furnace for melting a metallic or metal-containing bulk material in the shape of small pieces Expired - Lifetime EP1055354B1 (en)

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GB0311292D0 (en) * 2003-05-16 2003-06-18 Emp Technologies Ltd Improvements in and relating to the movement of metal
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