EP0273975A1 - Induction plasma furnace - Google Patents

Abstract

An induction plasma furnace comprises an inductor (1) housing a melting pot (2) the side wall of which consists of two vertically oriented sections (3) made of an electrically conductive material and electrically insulated from each other. At least one of the sections (3) of the pot (2) is connected in series with the electrical circuit of an electric arc plasmatron (7), said circuit being closed through the melt (4), so that the current direction of the arc (10) of the plasmatron (7) is the same or opposite to the current direction in the section (3) of the pot (2).

Description

Technical field

The invention relates to a field of electrical engineering and is particularly concerned with electrical heaters, namely a plasma induction furnace.

Underlying state of the art

The performance of different melting furnaces and the quality of the metal or alloy to be produced depend significantly on the type and intensity of movement of the melt in the crucible.

Each of the technological processes involved in melting a metal or an alloy, such as melting down the batch, overheating the entire melting volume, temperature compensation in the total volume of the melt, obtaining a homogeneous composition after the melt, and diffusion processes both in the melt itself and at the "melting point" Slag "," atmosphere melt "are intensified by the inevitable mixing, whereby the productivity of the process in the end is increased considerably.

Induction melting furnaces are largely known which contain an inductor with a crucible arranged therein, which is lined with a refractory lining. They ensure contactless energy supply to the insert in the crucible, i.e. Batch, melt or batch-melt mixture. The insert is mixed using the electromagnetic field of the inductor.

In induction melting furnaces operated at normal frequency (50 to 60 Hz), the speed of the melt is high, which ensures effective melting of the fixed insert and homogenization of the melt. However, there is increased wear of the crucible chuck and increased oxidation of the melt, which leads to contamination of the metal with inclusions of various types. Kind of leads. A metal ejection from the crucible is possible - such induction furnaces therefore have a limit in relation to the specific power to be supplied within 300 to 400 kW / t.

In furnaces operated at an increased frequency (150 to 10,000 Hz), the specific power to be supplied can be increased, but the speed of movement of the melt is significantly lower in these furnaces.

As is known, natural circulation in induction melting furnaces, in which the inductor is connected to a single-phase supply source, takes place in two circuits, which lie in the vertical plane, in the upper and lower part of the crucible, in each of which the melt of the insert circulates separately, by mixing is going on weakly. Such a circulation type in induction leads to the formation of a convex meniscus at the melt surface, whereby the required Men _- ge slag is increased, the rolling down to the walls of the crucible, the feed destroyed and contaminating the melt.

In addition, the increase in the amount of slag leads to a reduction in the refinability of the melt, since the slag is heated by the heat transfer from the melt.

In order to be able to improve the electrodynamic mixing of the melt in induction melting furnaces, devices are used in which the circulation of the insert is generated in a circuit with the aid of a running field which ensures that the insert is mixed over the entire crucible height while reducing the meniscus (AESlukhotsky , VSNemkov, NAPavlov, AVBamune, Ustanovka induktsionnogo nagreva. Energoizdat, Leningradskoe otdelenie / induction heating system, publisher Energoizdat, Leningrader Department /, 1981, pp. 246 to 247).

The insert can be heated and mixed both simultaneously and alternately. In the first case, separate inductors are used: a single-phase inductor for heating and a three-phase inductor for mixing, which uses electrostatic filters to protect the feed source against intrusion into which others are equipped. In the second case, the oven has a divided inductor, which is alternately connected to different food sources. However, if the supply circuit of the induction melting furnace is considerably complicated, only two types of circulation are generated: in two circuits - when connecting the inductor to a single-phase supply source, in a circuit - when connecting it to a three-phase supply source.

Plasmo induction furnaces are known which contain an inductor with a crucible arranged therein and an arc plasmatron, the circuit of which is closed via the melt. In comparison to induction melting furnaces, these furnaces make it possible, for example, to double the productivity of the process of melting metals and alloys, due to the combination of the local and the spatial heating of the insert. By heating the slags with the help of the plasma arc of the arc plasma matron, the quality of the metals and alloys to be produced is improved due to the in-depth refining of the melt to remove non-metallic inclusions and harmful substances.

Thanks to the use of the plasmatron, the melt; be treated with both inert and active plasma-forming gases. How the mixing process of use in plasma induction furnaces takes place is therefore of particular importance for the performance increase of the furnaces and the quality improvement of the metals and alloys to be obtained by melting.

A plasma induction furnace is also known, which contains an inductor with a crucible arranged therein, the side wall of which is cylindrical, and an arc plasmatron, the circuit of which is closed via the 5 melt located in the crucible (S.Asada. Dvukhtonnaya plazmenno-induktsionnaya pech na zavode g.Sibukava / 2 t - plasma induction furnace in the city factory Sibukava /, "Denki seiko", volume 47, No. T, 1976, pp. 60 to 63). The inner surface of the crucible is made of an electrical insulating material, and it is provided with a magnesite lining and provides the electrical insulation of the plasmatron circuit from the inductor circuit.

A bottom electrode for closing the plasmatron circuit is arranged in the bottom of the crucible. The inductor is connected to a single-phase supply source with an output frequency of 150 Hz. To mix the melt in the entire volume of the crucible, a three-phase system for electromagnetic mixing is provided, which contains three inductors, each of which is connected to a phase of a three-phase supply source with a frequency of 60 Hz. With this system, the circulation of the melt in two circuits can be changed to the circulation in one circuit and vice versa. The direction of the circulation in a circuit can be changed by appropriate switches in the feed circuit.

Such a constructive design of the plasma induction furnace considerably complicates the construction of the furnace, the external dimensions are enlarged, the costs are increased and the maximum power consumption when the insert is melted down is reduced.

With this system for mixing the melt, another type of circulation of the melt, which is required for other technological processes when melting metals and alloys, cannot be produced. For detoxifying and making slag is e.g. a directed movement of the melt at its mirror towards the drain opening is required, especially in processes with multiple slag making. In such an oven, the intensity and type of circulation, e.g. cannot be changed continuously from horizontal to vertical.

Disclosure of the invention

The invention has for its object a To create a plasma induction furnace with such a design of the crucible and such an electrical coupling of the crucible with a plasmatron, by means of which a predetermined type of circulation of the melt in the crucible can be generated depending on the technological process during the melting process and thus the performance of the plasma induction furnace can be increased.

The object is achieved in that, in the case of a plasma induction furnace which contains an inductor with a crucible arranged therein, the side wall of which is cylindrical, and an arc plasmatron, the circuit of which is closed via the melt located in the crucible, according to the invention the side wall of the crucible is perpendicular arranged sections is formed, which consist of a current-conducting material and are electrically insulated from one another, at least one of which is connected in series in the plasmatron circuit in such a way that the current direction in the plasmatron arc coincides with the current direction in the crucible section or is opposite thereto.

Such a constructive design of the crucible of the plasma induction furnace allows a predetermined type of circulation of the melt, depending on the technological process stage when metals and alloys are melted, due to the electromagnetic interaction of fields generated by the inductor current and the current in the sections of the crucible with those flowing in the melt Streams are created. The constructive design of the crucible according to the invention thus allows any type of circulation of the melt, which is required depending on the technological process step when melting metals or alloys, to be produced in the plasma induction furnace without the structure of the furnace having to be considerably complicated.

Brief description of the drawings

• Fig. 1 in schematischer Darstellung einen erfindungsgemässen Plasmainduktionsofen, bei dem eine Tiegelsektion an den Plasmatronstromkreis so angeschlossen ist, dass die Richtungen der im Plasmatronlichtbogen und in der Tiegelsektion fliessenden Ströme zusammenfallen (teilweiser Längsschnitt' ;
• Fig. 2 einen Schnitt gemäss der Linie II-II in Fig. 1, nach der Erfindung;
• Fig. 3 in schematischer Darstellung einen erfindungsgemässen Plasmainduktionsofen, bei dem eine Tiegelsektion an den Plasmatronstromkreis so angeschlossen ist, dass die Richtungen des im Plasmatronlichtbogen und in der Tiegelsektion fliessenden ströme einander entgegengesetzt sind (teilweiser Längsschnitt);
• Fig. 4 in schematischer Darstellung einen erfindungsgemässen Plasmainduktionsofen, bei dem sechs Tiegelsektionen an den Plasmatronstromkreis so angeschlossen sind, dass die Richtungen der im Plasmatronlichtbogen und in den Tiegelsektionen fliessenden Ströme einander entgegengesetzt sind (teilweiser Längsschnitt);
• Fig. 5 einen Schnitt gemäss der Linie V-V in Fig. 4, nach der Erfindung;
• Fig. 6 in schematischer Darstellung einen erfindungsgemassen Plasmainduktionsofen, bei dem sämtliche Tiegelsektionen an den Plasmatronstromkreis so angeschlossen sind, dass die Richtungen der im Plasmatronlichtbogen und in den Tiegelsektionen fliessenden Ströme zusammenfallen (teil_- weiser Längsschnitt);
• Fig. 7 eine Kennlinie der Krafteinwirkung auf die Schmelze von seiten des resultierenden elektromagnetischen Feldes im Querschnitt durch den in Fig. 1 dargestellten erfindungsgemässen Plasmainduktionsofen, die die Zirkulationsart der Schmelze näher erläutert;
• Fig. 8 (a, b) Kennlinien der Krafteinwirkung des elektromagnetischen Feldes auf die Schmelze im Längsschnitt durch den in Fig. 3 dargestellten erfindungsgemässen Plasmainduktionsofen, jeweils von seiten der an den Plasmatronstromkreis angeschlossenen Tiegelsektion und von seiten des restlichen Tiegelteils;
• Fig. 9 eine Zirkulationsart der Schmelze im Längsschnitt durch den in Fig. 3 dargestellten erfindungsgemässen Plasmainduktionsofen;
• Fig. 10 (a, b) Kennlinien der Krafteinwirkung des resultierenden elektromagnetischen Feldes auf die Schmelze im Längsschnitt durch den in Fig. 4 dargestellten erfindungsgemässen Plasmainduktionsofen;
• Fig. 11 eine Zirkulationsart der Schmelze im Längsschnitt durch den in Fig. 4 dargestellten erfindungsgemässen Plasmainduktionsofen;
• Fig. 12 (a, b) Kennlinien der Krafteinwirkung des resultierenden elektromagnetischen Feldes auf die Schmelze im Längsschnitt durch den in Fig. 6 dargestellten erfindungsgemässen Plasmainduktionsofen;
• Fig. 13 eine Zirkulationsart der Schmelze im Längsschnitt durch den in Fig. 6 dargestellten erfindungsgemässen Plasmainduktionsofen;

In the following, the invention is illustrated by means of specific exemplary embodiments and the attached drawings explained in more detail; show it:

• 1 shows a schematic representation of a plasma induction furnace according to the invention, in which a crucible section is connected to the plasmatron circuit in such a way that the directions of the currents flowing in the plasmatron arc and in the crucible section coincide (partial longitudinal section);
• 2 shows a section along the line II-II in Figure 1, according to the invention.
• 3 shows a schematic representation of a plasma induction furnace according to the invention, in which a crucible section is connected to the plasmatron circuit in such a way that the directions of the currents flowing in the plasmatron arc and in the crucible section are opposite one another (partial longitudinal section);
• 4 shows a schematic representation of a plasma induction furnace according to the invention, in which six crucible sections are connected to the plasmatron circuit in such a way that the directions of the currents flowing in the plasmatron arc and in the crucible sections are opposite one another (partial longitudinal section);
• 5 shows a section along the line VV in Figure 4, according to the invention.
• Are connected as a schematic representation of a plasma induction furnace according to the invention, in which all the sections to the crucible Plasmatronstromkreis Fig 6 that the directions of current flowing in the Plasmatronlichtbogen and into the crucible sections streams coincide (part _- fragmentary longitudinal section).
• 7 shows a characteristic curve of the force acting on the melt from the side of the resulting electromagnetic field in cross section through the plasma induction furnace according to the invention shown in FIG. 1, which explains the type of circulation of the melt in more detail;
• 8 (a, b) characteristics of the force of the electromagnetic field on the melt in longitudinal section through the plasma induction furnace according to the invention shown in FIG. 3, in each case from the side of the plasmatron circuit connected crucible section and on the part of the remaining crucible part;
• 9 shows a type of circulation of the melt in longitudinal section through the plasma induction furnace according to the invention shown in FIG. 3;
• 10 (a, b) characteristics of the force effect of the resulting electromagnetic field on the melt in longitudinal section through the plasma induction furnace according to the invention shown in FIG. 4;
• 11 shows a type of circulation of the melt in longitudinal section through the plasma induction furnace according to the invention shown in FIG. 4;
• 12 (a, b) characteristics of the force effect of the resulting electromagnetic field on the melt in longitudinal section through the plasma induction furnace according to the invention shown in FIG. 6;
• 13 shows a type of circulation of the melt in longitudinal section through the plasma induction furnace according to the invention shown in FIG. 6;

Preferred embodiment of the invention

The plasma induction furnace contains an inductor 1 (FIG. 1) with a crucible 2 arranged therein. Like inductors in known plasma induction furnaces, the inductor is designed in the form of a tube with a round or special cross-section, which lies near the helix around the crucible 2. The crucible 2 has the shape of a cylinder, its side wall being formed by vertically arranged sections 3 (FIGS. 1, 2) which consist of a current-conducting material, in particular of metal ceramic. In the embodiment of the plasma induction furnace shown in FIGS. 1, 2, five sections 3 are shown. Depending on the outer dimensions of the crucible 2, the number and the material of these sections 3 can be different. It is expedient that _S ektionsanzahl within 5 to 35 select, which optimal energy parameters of the plasma induction furnace _z . _B. the efficiency, the performance can be guaranteed.

The sections 3 of the crucible 2 can also be made from other current-conducting materials such as graphite, metal.

The sections 3 are electrically insulated from one another by electro-insulating layers 6 consisting of magnesite, which lie between the sections 3 and have been applied to the surfaces of the sections 3 facing the inside of the crucible 2, to the bottom 5, to the end faces of the sections 3. The thickness of each layer 6 depends on the material and application method of the electrical insulation. The electrical insulation made of Al203 can, for example, be applied using the vapor deposition method.

The plasma induction furnace also contains a DC arc plasmatron 7 (Fig. 1). The plasmatron 7 is mounted in the lid 8 of the crucible 2 and causes the batch 9 to be heated and melted down with the aid of a plasma arc 10. The inner surface of the lid 8 is provided with a lining layer 11. A segment-shaped part 12 (FIG. 2) of the crucible 2 (FIG. 1) lying in the vicinity of one of the sections 3 of the crucible 2 is insulation-free. This part 12 (FIG. 2) serves to supply current to the melt 4 (FIG. 1), via which the circuit of the plasmatron 7 is closed.

In the embodiment in question, the section 3 of the crucible 2, to which the part 12 (FIG. 2) of the base 5 (FIG. 1) adjoins, is connected to the circuit of the plasmatron 7. The current direction in the arc of the plasmatron 1 ₀ 7 coincides with the direction of current in the section 3 together (in Fig. 1, the current directions are indicated with arrows). _{Power supply terminals} 13, 14 of the _plasma t _{rons 7} are connected to a supply source, in the embodiment in question - to a direct current source.

An AC power source can be used as the power source. If a DC plasmatron is used it is connected to the AC power source via a rectifier. Only one AC power source is used for the AC plasmatron. When using an AC power source, a power source can be used for the inductor.

Dei one of the terminals - 13 - is connected to the bottom 5 of the crucible 2 and the other terminal 14 to a power supply 15 arranged in the upper part of section 3, while another power supply 16, which is located in the lower part of this section 3, with the plasmatron 7 is connected.

. In the embodiment shown in Figure 3 embodiment of the Plaemainduktionsofens the section 3 to the power is _- _ circle of the plasmatron 7 connected so that the Stremrichtungen in opposite directions in the section 3 and in the arc 10 of the plasmatron 7. The power supply 15 is connected to the terminal 13 and the Plasmatron 7 to the terminal 14. The bottom 5 of the crucible 2 is completely covered with the electrical insulating layer 6, while a part 17 of the inner surface of the section 3, which is connected to the circuit of the plasmatron 7, is insulation-free and serves to supply current to the melt 4.

Fig. 4 shows a plasma induction furnace, the crucible 18, which is enclosed by an inductor 19 designed in a known manner, contains twelve sections 20 (Fig. 5), which are designed with a cooled composite crucible as in known induction furnaces. Each section 20 is made of a metal, e.g. made of copper, and has a circulation channel 21 for a coolant, as which water, gas, cryogenic liquid can be used.

The sections 20 are electrically isolated from one another with the aid of electrical insulating layers 22, 23, for example made of Al ₂ O ₃ , which have been applied by vapor deposition to the surfaces facing the inside of the crucible 18 and to one another. On the surfaces facing the interior of the crucible 18, an electric device can also be used insulating layer, for example made of magnesite or alundum.

The lid 24 of the crucible 18 was made similar to the lid 8.

In order to be able to change the type of circulation of the melt 4 under the effect of the inductor 19 which is designed analogously to the inductor described in FIG. 1, six sections 20 (FIG. 5) of the crucible 18 (FIG. 4) which are connected to one another in parallel are replaced by every second one in Series connected to the circuit of the plasma cartridge 7 so that the current directions in the arc 10 of the plasma cartridge 7 and in the sections 20 are opposite. The power supply lines 25 arranged in the upper part of these sections 20 are interconnected and connected to the terminal 13. The lower part of each of the sections 20 is connected to the floor 27 via power supply lines 26. A coolant circulation channel 28 is provided in the bottom 27, and the surface of the bottom 27 facing the interior of the crucible 18 is covered with an electrical insulating layer 29. To supply current to the melt 4, an annular part 30 (FIG. 5) of the base 27 adjoining the sections 18 is insulation-free.

FIG. 6 shows an embodiment of the plasma induction furnace similar to that shown in FIGS. 4, 5, in which all sections 20 of the crucible 18 are connected to the circuit of the plasma cartridge 7 in such a way that the current directions in the arc 10 and in the sections 20 coincide . For this purpose, the current leads 31 arranged in the upper part of the sections 20 are connected to the terminal 14 and the current leads 32 located in the lower part of the sections 20 are connected to the Plasmatron 7. The bottom 27 is completely insulation-free and connected to the terminal 13.

The force F of the electromagnetic field on the melt 4 is indicated in FIG. 7, 8a, b, 10a, b, 12a, b with arrows. The type of circulation of the melt 4 is in the plasma induction furnaces shown in FIGS. 1, 2, 3, 4, 5, 6 with closed lines "1" in FIG ^. 7, 9, 11, 13 indicated.

The plasma induction furnace is operated as follows.

After the fixed insert 9 has been placed in the crucible 2 (FIG. 1), the cover 8 is closed and the plasmatron 7 is brought into the ignition position of the arc 10. Then a voltage is supplied to the inductor 1 and the plasmatron 7 and the arc 10 is ignited.

Under the action of the arc 10 of the plasmatron 7 and the electromagnetic field of the inductor 1, the insert begins to melt down. The arc 10 melts the insert layer quickly through its thickness, burns between the surface of the melt 4 and the plasmatron 7 and gives off its heat intensively to the surrounding insert. Depending on the melting of the insert and the increase in the amount of the melt 4, the length of the arc 10 becomes shorter, the conditions for the heat emission from the arc 10 to the melt 4 deteriorate. At the same time, the conditions for supplying energy from the inductor 1 to the melt 4 are improved. Since the main part of the energy in the process stage remelting of the insert 9 and overheating of the melt 4 is supplied by the inductor 1, the circulation of the melt 4 takes place in natural two cycles, which has a favorable effect on the exchange of hot material. Thereafter, to remove harmful accompanying substances on the surface of the melt 4 in the crucible 2 through special holes (not shown in the drawing) in the Dickel 8, a slag is added to the superheated melt 4 in portions in a predetermined order.

In order to evenly distribute the slag over the entire surface of the melt 4 in the crucible 2 and to heat it uniformly, the circulation of the melt 4 of such aft is brought about, which is shown with closed lines "1" in FIG. 7. For this purpose, the voltage at inductor 1 is continuously reduced or the voltage at terminals 13, 14 increases, which in the first case leads to the current draw in the inductor 1 and in the second case to the current increase in the circuit of the plasmatron 7.

Due to the same current directions in section 3 and in the arc 10 and consequently in the melt 4, the force F (FIG. 7) on the melt 4 (FIG. 1) is weakened by the section 3 connected to the circuit of the plasmatron 7, which leads to the circulation of the melt 4 in the horizontal plane in the entire volume of the crucible 2. In this type of circulation, the surface of the melt 4 has no meniscus, and a continuous supply of the slag under the arc 10 of the plasmatron 7 is ensured, its melting and heating accelerating, which leads to an increase in the furnace output. The homogeneity of the melt 4 in the total volume of the crucible 2 is also improved. This constructive design of the crucible 2 makes it possible to rapidly change the type of movement of the melt from the circulation in the vertical plane to the circulation in the horizontal plane by continuously changing the current in the inductor 1 or in the arc 10 of the plasmatron 7.

When melting high-purity metals and alloys, multiple slagging and deslagging is required according to the technology. When using the plasma induction furnace shown in FIG. 4, the detoxification process from the crucible 2 can be accelerated. The type of circulation of the melt 4 is indicated by the closed line "1" (FIG. 9), by means of which the melt 4 (FIG. 3) is mixed at the total height of the crucible 2. On the part of the upper part of the section 3 connected to the circuit of the plasmatron 7, a force F ₁ (FIG. 8 a) on the melt 4 (FIG. 3) is generated on the section provided with the electrical insulating layer 6, which is stronger than the force F ₂ (Fig. 8b) on the part of the remaining part of section 3 (Fig. 3) because the currents in section 3 and the arc 10 are directed in opposite directions.

By a continuous change in current in the inductor 1 and in the circuit of the plasmatron 7, by changing the ratio of F ₁ to F ₂ , the predetermined type of circulation is generated, in which the accumulation of the used slag at the tapping point is ensured for its removal.

Refractory metals and alloys, e.g. Tungsten are usually melted in a plasma induction furnace with the cooling crucible 18 (FIGS. 4, 5, 6). Before the voltage supply to the inductor 19 and the plasmatron 7, a coolant is introduced into the channels 21 of the sections 20 and the channel 28 of the base 27, which coolant circulates during the entire melting process. After the voltage supply to the inductor 19 and the plasma tran 7, the arc 10 is ignited. A section flows through the sections 20 connected to the circuit of the plasma cartridge 7, the direction of which is opposite to the current direction in the arc 10 of the plasma cartridge 7. Depending on the increase in the amount of the melt 4 under the action of the electromagnetic field from the inductor 19, the melt 4 is mixed thoroughly, and the surface of the melt 4 acquires a convex shape. The current of the arc 10 flowing through the melt 4 will strive to flow along the surface of the melt 4 in the vicinity of the electrically insulated sections 20 connected to the circuit of the plasma cartridge 7.

A component of the force of the electromagnetic field of the sections 20 on the current flowing through the arc 10 and the melt 4 thus arises in the upper part of the melt 4 and is directed downward to the bottom 27 of the crucible 18. As the base 27 approaches, the size of this component decreases. Depending on this approach, the component directed from the periphery towards the center of the melt 4 of the similar interaction of the electromagnetic field generated by the current in the sections 20 with the current flowing through the melt 4 increases, thereby pushing back. the melt 4 is increased by the sections 20 of the crucible 18. This firstly reduces heat losses and promotes the integrity of the electrical insulation layer of the sections 20 against destruction, and secondly increases the height of the column of the melt 4, so that the zone of contact of the melt 4 with the insert is enlarged and an effective absorption of the insert by the melt 4 in motion and a resolution in it can be increased. The resulting force F (Fig. 10a, b) on the melt 4 (Fig. 4) makes it possible to circulate in a circuit of the type "1" (Fig. 11) with a discharge of the melt 4 (Fig. 4) together with the insert to be picked up by it along an axis under the arc 10, thereby shortening the melting time of the insert and promoting an increase in the homogeneity of the melt 4 towards the end of this period, the melt 4 being at the total height of the crucible 18 is mixed.

In the plasma induction furnace shown in FIG. 6, during the remelting and overheating of the melt 4, the specific power to be supplied by the inductor 19 can be increased in that, as a result of the connection of the sections 20 of the crucible 18, their current direction with the current direction in the arc 1: 0 of the plasmatron 7 coincides, the resulting force F (FIG. 12a, b) of the electromagnetic field from the inductor 19 on the melt 4 (FIG. 6) can be weakened on the circuit of the plasmatron 7. Under the effect of F (Fig. 12a, b) the circulation type "1" (Fig. 13) is similar to the circulation taking place under the effect of the electromagnetic field from the inductor 19, only the speed of movement of the melt 4 changes Period through the inductor 19 of the melt 4 to be supplied leads to an increase in the furnace output.

Industrial applicability

The present plasma induction furnace can preferably be used in the metallurgical industry, in technological processes when melting different metals and alloys, e.g. on the tungsten, molybdenum basis, especially in processes associated with the use of highly active hot slags.

Claims (1)

Plasma induction furnace which contains an inductor (1, 19) with a crucible (2, 18) arranged therein, the side wall of which is cylindrical, and an arc plasmatron (7), the circuit of which is via the melt (4) located in the crucible (2, 18) ) is closed, characterized in that the side wall of the crucible (2, 18) is formed by vertically arranged sections (3, 20), which consist of a current-conducting material and are electrically insulated from one another, at least one of those with the circuit of the plasma cartridge (7) is connected in series in such a way that the current direction in the arc (10) of the plasma cartridge (7) coincides with the current direction in the section (3, 20) of the crucible (2, 18) or is opposite.

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