EP1339885B1 - Method for producing metal blocks or bars by melting off electrodes and device for carrying out this method - Google Patents

Description

The invention relates to a method for producing blocks or strands of metal - in particular of steels and Ni and Co base alloys - by melting self-consuming electrodes in an electrically conductive slag bath using alternating or direct current in a short, downwardly open water-cooled mold, via which a current contact is made to the slag bath and which is associated with a bottom plate. In addition, the invention covers an apparatus for carrying out this method.

In the production of remelt ingots by the process of electroslag remelting in chill molds - but also in short chill molds - it is customary to set a melting rate in kilograms (kg) per hour, depending on the segregation susceptibility of the remelted alloy; and 110% of the block diameter in millimeters (mm). In the case of block shapes deviating from the round cross section, such as square or flat formats, it is possible to work with an equivalent diameter, which is calculated from the cross section circumference divided by the number Π (Pi). The lower range is mainly used for high-saline alloys - such as tool steels or high-alloy nickel base alloys - in which a shallow metal sump is aimed at to avoid segregation. However, the value of 70% can hardly be undershot in the conventional ESU process, because then the power supply from the Abschmelzelektrode must be greatly reduced in the slag, which is a low temperature of the slag and subsequently a poor, often rillige surface of the remelt entails. If the power is too low In many cases, slag bath also forms a thick slag coat between the block and the mold, which in turn hinders the removal of heat from the block surface, so that the desired flat melt pool can not be achieved again. On the other hand, even with less segregation-sensitive steels and alloys, a value of 110% in conventional electroslag remelting, the so-called ESU method, not be exceeded, otherwise the overheating of the slag bath together with the increased melting rate for inadmissibly deepened melt sump and thus a undesirably coarse block structure - associated with segregation - has the consequence. As can be easily seen from the above, in the conventional ESU process, in which the melt stream is passed into the slag bath via the meltdown electrode and redissociated via the remelted block and bottom plate, the slag bath temperature and the meltdown rate are - and in context so that sump depth as well as formation of the surface - are closely linked and can not be controlled and controlled independently of each other and separately.

When producing large diameter reflow ing blocks of 1000 mm and above, it is found that compliance with the above-mentioned desired low melting rates, especially when using large diameter ablation electrodes, corresponding to 65 to 85% of the die diameter, results in too low a slag bath temperature, which in turn results in a bad, often ridiculous surface on the remelt block. Increasing the power supply to the slag bath in this case, although this results in an improvement of the block surface, but at the same time increases the Abschmelzrate over the allowable limit, resulting in a deeper melt sump and unfavorable solidification. This increase in the melting rate with increased power supply to the slag bath occurs because, on the one hand, the consumable electrode serves to supply energy to the slag bath, but on the other hand, all the more melts faster, the more you increase the energy supply to the slag bath. The electrode must then be tracked at the rate in the slag bath with which it melts. If the Abschmelzelektrode not tracked, it would melt to just above the Schlackenbadoberfläche, whereby the electrical contact and thus the power supply to the slag would be interrupted. The remelting process would thus come to a standstill.

Another way to increase slag bath temperature is to remelt smaller diameter electrodes. In this case, the end face of the electrode immersed in the slag bath is smaller, so that a comparatively hotter slag bath is needed to achieve the desired melting rate. While many improvements in the block surface can be achieved with this approach, the use of small diameter electrodes results in an increased heat concentration in the center of the block, which can result in a V-shaped sump with increased tendency to segregation.

All the above Difficulties are causally connected with the fact that, on the one hand, the melting rate of the electrode is controlled by the energy supplied to the slag bath via the electrode and, on the other hand, this energy supply must be sufficient to keep the melt pool sufficiently fluid up to its edge and a temporary progression of the To prevent solidification over the meniscus of the enamel. If, due to an excessively low temperature of the slag bath, such a solidification progress temporarily passes over the meniscus, this results in the formation of a rough surface unfavorable for the further processing of the blocks.

Of the EP 786 521 B1 The Applicant can be found in a process for electroslag remelting, wherein by melting of electrodes comparatively large through-higher Abschmelzraten be set as the conventional electroslag remelting. In the method described, the return of a portion of the melt stream via carried out in the mold wall electrically conductive elements. The arrangement leads to a division of the return currents inversely proportional to the total resistance of inserted conductor loops.

The DE 196 14 185 C the Applicant describes a short, water-cooled, downwardly open mold for the ESU process or continuous casting process, in which the meniscus of the casting mirror is covered by an electrically conductive slag and does not contain directly water-cooled, current-conducting elements in the region of the slag bath above the casting mirror, via which a contact to a power source can be produced. As materials for these current-conducting elements graphite or a refractory metal - for example, W, Mo, Nb od. Like. - Used. In a particular embodiment, the current-conducting elements can be electrically insulated from the water-cooled part as well as from one another by non-water-cooled, non-conductive elements, for example made of ceramic.

In the SU-A-1 768 657 An arrangement for electroslag remelting in stand-up molds is discussed in which the mold is insulated from the bottom plate. The entire melt stream is fed via the electrode to the slag bath. This allows the derivation of a through the The DE 196 14 182 C the Applicant describes a short, water-cooled, downwardly open mold for the ESU process or continuous casting process, in which the meniscus of the casting mirror is covered by an electrically conductive slag and does not contain directly water-cooled, current-conducting elements in the region of the slag bath above the casting mirror, via which a contact to a power source can be produced. The materials used for these current-conducting elements are graphite or a refractory metal, for example W, Mo, Nb or the like. In a particular embodiment, the current-conducting elements can be electrically insulated from the water-cooled part and from one another by non-water-cooled elements which are not made of ceramic, such as ceramic. In this document, attention is drawn to a modified electroslag process for strand melting of small strand-like cross sections in either continuous casting-like straight molds or in - belonging to the prior art - upwardly T-shaped expanded molds, where appropriate, the required power for the desired Abschmelzrate or current through the Gießquerschnitt alone can not be derived, otherwise there is an overheating of the metal sump and continue to come back to the formation of an unfavorable solidification structure. It is mentioned that in Japan attempts have been made to divert a portion of the stream from the slag bath over the mold wall, but there is the appearance of micro-arcs between the meniscus of the slag bath and the mold wall. This leads to an erosion of the copper of the mold at the height of the slag bath and thus to a significant reduction in Kokillenstandzeit.

In the SU-A-1 768 657 An arrangement for electroslag remelting in stand-up molds is discussed, in which the mold is insulated from the bottom plate. The entire melt stream is fed via the electrode to the slag bath. This allows the derivation of a resistance-controlled partial flow from the slag bath via the mold back to the current source designed as a DC power source, which is arranged so that the consumable electrode as the anode and the remelting as Cathode are connected. The greater the proportion of the partial flow discharged via the block in relation to the total flow introduced via the electrode, the better the desulfurization should be. Between the block and the mold, a potential difference should be set which is small enough to avoid so-called flashovers, which in themselves are caused by the fact that a potential difference builds up between the mold and the block and the slag skin adhering to the block is not always and not at all Represent a sufficient resistance to a current transfer between mold wall and block surface represents. A partial flow is to be directed from the mold directly back to the power supply, although the discharge of all the current across the block and electrode would give a better result in terms of desulfurization.

Resistance controllable partial flow from the slag bath on the mold back to the current source designed as a DC power source, which is arranged so that the Abschmelzelektrode are connected as the anode and the Umschmelzblock as a cathode. The larger the proportion of the partial flow discharged via the block in relation to the total flow introduced via the electrode, the better the desulfurization should be. Between the block and the mold, a potential difference should be set which is small enough to avoid so-called flashovers, which in themselves are caused by the fact that a potential difference builds up between the mold and the block and the slag skin adhering to the block is not always and not at all Represent a sufficient resistance to a current transfer between mold wall and block surface represents. A partial flow is to be directed from the mold directly back to the power supply, although the discharge of all the current across the block and electrode would give a better result in terms of desulfurization.

Knowing these circumstances, the inventor has set the goal of being able to control the melting rate of the electrode independently of the temperature of the slag bath and at the same time to ensure a good block surface.

To achieve this object, the teaching of the independent claim; the Ünteransprüche give favorable developments.

The solution of the above outlined object succeeds in a surprising simple manner, if for the melting of self-consuming electrodes under slag a known mold with built in the mold wall in the slag bath and against the lower, the Umschmelzblock forming part of the mold, electrically insulated current-conducting elements is used. This makes it possible, on the one hand, to heat the slag bath independently of the electrode feed by supplying energy via the mold wall, so that the metal sump can be kept liquid up to the edge over the meniscus. On the other hand, the consumable electrode melting rate can be easily controlled by the feed rate will be pushed with it into the overheated slag bath.

The Abschmelzelektrode can be completely de-energized. But it is also possible to lead a partial flow through the electrode. The Umschmelzblöcke formed in the lower part of the mold can be pulled out of this either down or the mold is raised in the manner in which the block standing on a bottom plate grows.

The present invention is therefore a process for the production of blocks or strands of metals, in particular of steels and Ni and Co base alloys by melting self-consuming electrodes in an electrically conductive slag bath in a short, downwardly open water-cooled mold over which in known manner, a current contact to the slag is produced, wherein the supplied melt stream controlled controllably introduced both via the Abschmelzelektrode and on the mold in the slag with respect to the distribution of the current between the electrode and mold and the return of the melt stream both on the mold and on optionally returning the block and bottom plate; the distribution of the streams is adjusted by means of a controlled control and constructed on the bottom plate block relative to the mold either by raising or lowering of the bottom plate moves and held the metal or slag in the mold.

In addition, it has proved to be favorable that the proportion of current supplied via the consumable electrode can be from 0 to 100% of the total supplied melt stream. The proportion of the stream returned to the melt power supply via the bottom plate may also be 0 to 100% of the total melt flow returned.

This method described here in principle can be adapted in many ways to the requirements of the operator.

For example, the short, electrically conductive mold can be permanently installed in a working platform and the remelting block can be pulled down.

But it can also be built on a fixed base plate block and the mold are raised in the manner in which the block grows. The removal of the block or raising the mold can be done continuously or stepwise.

As low it has also been proven that supply and return are interchanged for the current, in particular DC is used. In addition, the resulting strand should be continuously or gradually withdrawn from the mold.

It is also possible to oscillate the mold, which may be of particular interest in a continuous block withdrawal.

In the case of a gradual Blockabzugs- or Kokillenhubbewegung may in addition to each lifting step immediately connect a Gegenhubschritt, wherein the stride length of the Gegenhubschritts can be up to 60% of the stride length of the Abziehshubschritts.

If, according to the invention, a direct-current power source is used as the melt current supply, then the supply line with all the above-mentioned variants can be connected either as a cathode or as an anode by incorporating a pole-changing switch in each of the two melt current supplies.

Also, it has proved to be favorable, by replacing the electrodes in the inventive plants in per se known Way even long Umschmelzblöcke - regardless of the electrode length - produce.

In the context of the invention, a short water-cooled mold with associated bottom plate and at least two provided in the slag bath current-conducting element is used in which the supply of the melt stream of at least one power source to both the Abschmelzelektrode and at least one current-conducting element of the mold either individually or is jointly adjustable by a suitable control arrangement, and that the return line to the at least one power source of both at least one current-conducting element of the mold and the Umschmelzblock supporting movable in the longitudinal axis of the mold base plate is selectively adjustable either individually or jointly by a control arrangement.

Preference is given to two independently controllable current sources, one of which is connected to the Abschmelzelektrode, whereas the other power source connects both to the Abschmelzelektrode and to the current-conducting element.

From the power source 'one lead to Abschmelzelektrode and another lead to the current-conducting element to be guided or it lead to the power source return lines from the bottom plate and the current-conducting element. The power source may be a rectifier system whose polarity is reversible.

As low, it has been proven that a plurality of insulating elements separate electrically conductive elements are arranged in a horizon of the mold. The latter form according to the invention with the insulating a ring, optionally with two current-conducting elements are present, one of which is connected to the supply line and one to the return line.

It is also within the scope of the invention that the distribution of the current intensities between the individual supply and return lines can be set by adjustable resistors.

Fig. 1, 2, 4:

jeweils einen Längsschnitt durch eine Gießeinrichtung für Metalle mit Kokille ; Zeichnung 2 ist gemäß der Erfindung.

Fig. 3:

einen vergrößerten Schnitt durch Fig. 2 nach deren Linie III - III.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; this shows in:

1, 2, 4:

in each case a longitudinal section through a casting device for metals with mold; Drawing 2 is according to the invention.

3:

an enlarged section through Fig. 2 according to their line III - III.

A water-cooled mold 10 with hollow annular mold body 12 is according to Fig. 1 from the bottom, on the one hand hollow - bottom plate 14 associated with the outer diameter is slightly shorter than the inner diameter d of the mold 10; the bottom plate 14 can be inserted so far into the mold opening or the inner mold cavity 11 of the height h for starting the plant, until it extends directly below the upper edge 13 of the Kokillenhohlkörpers 12.

On the upper edge 13 rests a ring-like insulating member 16 and on this one - also ring-like and / or formed of several parts - current-conducting element 18; The latter is electrically insulated from the - non-conductive the current - insulating elements 16 against the water-cooled lower portion 20 of the mold 10 and upwardly separated by an upper insulating member 16 _a from a water-cooled hollow ring 22 as the upper region. However, for the inventive use of the system described here, the upper insulating 16 _{a is} not absolutely necessary.

On the bottom plate 14, below a slag bath 24 and a sump 26 covered by it, a lower one produced by a remelting process with a self-consumable electrode 28 is stored, in that water-cooled lower one For example, to start the process, liquid slag may be poured into the mold gap bounded by the mold 10 and the electrode 28 until the slag level 25 of the resulting slag bath 24 is about the upper edge of the current conducting element 16 _{a has} reached.

The electrode 28 on the one hand and the bottom plate 14 on the other hand are connected via high current lines 32, 34 with one pole of a DC or AC source 36; from the line 32 branches off a high current line 32 _a , which is connected at the other end to the current conducting element 18. The supply of the melt stream to the slag 24 takes place from that AC or DC source 36 - depending on the position of these connected by the lines 32, 32 _a high current contacts 38, 39 - either only via the electrode 28 or only via the current-conducting element 18th the mold 10 or via electrode 28 and mold 10 at the same time, wherein the proportion of current flowing through the electrode 28 and the Stromleitelement 18 current through adjustable resistors 42 and 42 _a - or other comparable in the effect facilities - set as desired can be. The return of the entire melt stream is carried out in this arrangement exclusively on the remelting block 30 and the lowerable bottom plate 14 through the return line 34th

In an inventive arrangement according to Fig. 2 is the mold 10 with at least two insulating elements 16, 16 _a both against each other and against the lower portion 20 of the mold 10 and - here mandatory - against the upper portion 22 of the mold 10, namely those hollow ring 12, insulated Stromleitelementen 18, 18 _a equipped. Fig. 3 For this purpose, two partial circuit-shaped current-conducting elements 18, 18 _a can be seen, which are separated from each other by correspondingly shaped insulating elements 16 _b, forming a ring with them; become - as described here - two or more lying at different potentials Stromleitelemente 18, 18 _a required, they can be formed in particular in molds 10 laid around a longitudinal axis A circular cross section circular as a ring and arranged one above the other and by the intervening - also annular - insulating 16 isolated from each other.

If the return via a Stromleitelement 18 in the mold 10 and the bottom plate 14 together, so allow controllable resistors 44 and 44 _a in the bottom plate 14 to the power source 36 connecting return line 34 and a current source 36 to the / the Stromleitelement / e 18th adjoining and attached to the return line 34 line 35 - or another similar in effect means - adjusting the flowing back over the bottom plate 14 current component.

In Fig. 4 an arrangement for carrying out a method with two parallel controllable current sources 36, 36 _a for the melt power supply is shown. In this case, the supply of the melt stream of each of the two current sources 36, 36 _a individually or collectively either only to the electrode 28 or only to the current-conducting element 18 _a - or to both together -, depending on the position of the high-current switch 38, 38 _a , 38 _b and 39 in the lines 32 and 32 _a and the high-current switch 38 _b in the branch line 32 _n between the power source 36 _a and electrode 28th

The return of the melt stream can also be done individually or jointly to one of the two current sources 36, 36a or to both together from the current element 18 in the mold 10 and / or the bottom plate 14, depending on the position of the arranged in the return line 34 and 35 high-current switch 40, 40 _a and 41 or the high-current switch 40 _b in a return line 34 to the second current source 36 _a connecting branch line 34 _n . The switching capabilities of this arrangement when using AC are listed in Table 1 below. Their revelation is of particular importance. Table 1 Circuit options for two power supplies and electrically conductive mold circuit transformer supply return closed to / back open to / back 1 36 electrode block 38,38b / 40,40a 39,38b / 41,40b 2 36 electrode mold 38,38b / 41,40a 39,38b / 40,40b 3 36 electrode Block & mold 38,38b / 40,41,40a 39,38b / 40b 4 36 mold block 39 / 40,40a 38,38a, 38b / 41.4 5 36 mold mold 39 / 41,40a 38,38a, 38b / 40.4 6 36 mold Block & mold 39.40 / 41,40a 38,38a, 38b / 40 7 36 Electr. & Coke. block 38,39,38a / 40,40a 38b / 41,40b 8th 36 Electr. & Coke. mold 38,39,38a / 41,40a 38b / 40,40b 9 36 Electr. & Coke. Block & mold 38,39,38a / 40,41,40a 38b / 40b 10 36a electrode block 38,38b / 40,41a 39,38a / 41,40a 11 36a electrode mold 38,38b / 41,40b 39,38a / 40,40a 12 36a electrode Block & mold 38,38b / 40,41,40a 39,38a / 40a 13 36a mold block 39,38a, 38b / 40,40b 38 / 41,40a 14 36a mold mold 39,38a, 38b / 41,40b 38 / 40,40a 15 36a mold Block & mold 39,38a, 38b / 40,41,40b 38 / 40a 16 36a Electr. & Coke. block 38,39,38a, 38b / 40,40b - / 41,40a 17 36a Electr. & Coke. mold 38,39,38a, 38b / 41,40a - / 40,40a 18 36a Electr. & Coke. Block & mold 38,39,38a, 38b / 40,41,40b - / 40b 19 36 + 36a electrode block 38,38a, 38b / 40,40a, 40b 39/41 20 36 + 36a electrode mold 38,38a, 38b / 41,40a, 40b 39/40 21 36 + 36a electrode Block & mold 38,38a, 38b / 40,41,40a, 40b 39 / - 22 36 + 36a mold block 39,38a, 38b / 40,40a, 40b 38/41 23 36 + 36a mold mold 39, 38a, 38b / 41, 40a, 40b 38/40 24 36 + 36a mold Block & mold 39,38a, 38b / 40,41,40a, 40b 38 / - 25 36 + 36a Electr. & Coke. block 38,39,38a, 38b / 40,40a, 40b - / 41 26 36 + 36a Electr. & Coke. block 38,39,38b / 40,40a, 40b 38a / 41 27 36 + 36a Electr. & Coke. mold 38,39,38a, 38b / 41,40a, 40b - / 40 28 36 + 36a Electr. & Coke. mold 38,39,38b / 41,40a, 40b 38a / 40 29 36 + 36a Electr. & Coke. Block & mold 38,39,38a, 38b / 40,41,40a, 40b - / - 30 36 + 36a Electr. & Coke. Block & mold 38,39,38b / 40,41,40a, 40b 38 / -

The electrode and the slag bath can be protected against the ingress of air by gas-tight hoods (not shown here) which can also be sealed against the mold flange. Thus, the remelting under controlled atmosphere and exclusion of atmospheric oxygen take place, which also allows the production of ultrahigh remelting strands and prevents burning of oxygen-related elements.

Example according to FIG. 1:

An experiment was carried out on an ESU system with lifting skirts 10, in which the power supply to the slag bath 24 was conducted via the melting electrode 28 as well as the mold 10 and the return line via the block 30 and the bottom plate 14. mold: Cylindrical mold with a diameter of 500 mm with an electrically conductive ring in the area of the slag bath, which was electrically insulated from the lower part. consumable: 320 mm diameter stole Ck 45

After melting of 75 kg of slag composition 30% CaO, 30% Al ₂ O ₃ , 40% CaF 2, the entire melt stream was first passed over the electrode and remelted by the conventional ESU process until the slag mirror with the Kokillenring with the power supply line covered. Up to this point about 470 kg had melted away from the electrode. The melt rate was last 460 kg / h with a power supply to the slag bath of 450 kW, the current 8.0 kA at 58 V secondary voltage. From this point on, the mold stroke was adjusted so that the steel mirror was about 30 to 50 mm below the insulation was kept against the current-conducting ring of the mold and thus always in the range of the slag bath. After reaching the current-conducting ring, there was a division of the melt current between the current-conducting ring and the consumable electrode, at the same time the transformer voltage was lowered to 44 V.

As a result, the current through the electrode went back to 6.1 kA, while a current flow through the mold of 11.4 kA was established. The corresponding active power amounted to 27 kW at the electrode and 385 kW via the mold. The melting rate decreased to 390 kg / h under these conditions. With these conditions was about 3.5 hours. melted. Subsequently, the energy supply to the electrode was switched off, so that the supply of the melt stream took place exclusively via the mold. The voltage at the transformer was again increased to 55 V, which resulted in an increase of the mold current to 13.9 kA. The power input to the slag bath was 480 kW, while at the same time the melting rate decreased to 275 kg / h.

After another two hours, the power was turned off and the block was removed from the plant. The block produced had a smooth surface over the entire length, and especially in the upper part, built up at a low melting rate, which had no grooves or overlaps. The structure of the block produced after forging was impeccable over the entire length.

Claims (16)

1. Process for producing blocks or bars made from metal, in particular from steels and Ni-based and Co-based alloys, by melting off self-consuming consumable electrodes in an electrically conductive slag bath using alternating current or direct current in a short water-cooled ingot mould which is open at the bottom, by means of which a current contact with the slag bath is produced and to which is assigned a base plate, characterised in that the melting current is introduced into the slag bath both via the consumable electrode and via the ingot mould, in that the distribution of the melting current between consumable electrode and ingot mould is thus regulated in controlled manner and in that the return of the melting current is carried out alternatively both via the ingot mould and via the block and the base plate, wherein the division of the currents is adjusted in controlled manner by means of regulation and the block produced on the base plate is moved relative to the ingot mould either by raising the latter or by lowering the base plate and the metal level or slag level in the ingot mould is kept constant.
2. Process according to claim 1, characterised in that the proportion of the total supplied melting current supplied via the consumable electrode is selected between 0 and 100%.
3. Process according to claim 1, characterised in that the proportion of the melting current returned from the base plate is selected between 0 and 100%.
4. Process according to one of claims 1 to 3, characterised in that supply and return for the current are reversed, wherein in particular direct current is used.
5. Process according to one of claims 1 to 4, characterised in that the resulting bar is withdrawn continuously from the ingot mould.
6. Process according to one of claims 2 to 4, characterised in that the bar formed is withdrawn step-wise from the ingot mould.
7. Process according to claim 4 or 6, characterised in that an oscillating movement is executed by the ingot mould.
8. Process according to claim 5 or 7, characterised in that a counter-stroke step in opposite direction immediately follows each stroke step, wherein the stroke length of the counter-stroke step is at the most 60% of the stroke length of the preceding stroke step.
9. Device for carrying out the process for producing blocks or bars made from metal, in particular from steels and Ni-based and Co-based alloys, by melting off self-consuming consumable electrodes (28) in an electrically conductive slag bath (24), according to one of the preceding patent claims, using a short water-cooled ingot mould (10) having assigned base plate (14) and having at least two current-conducting elements (18, 18a) provided in the region of the slag bath (24), and which are insulated with respect to the lower region (20) of the ingot mould (10) shaping the melted-down block (30) and optionally against other current-conducting elements, characterised in that the supply (32, 32a) of the melting current can be adjusted specifically by at least one current source (36, 36a) both for the consumable electrode (28) and for at least one current-conducting element (18) of the ingot mould (10) either individually or together by a suitable regulating arrangement, and in that the return (34, 35) to the at least one current source can be adjusted specifically both by at least one current-conducting element (18a) of the ingot mould (10) and the base plate (14) supporting the melted-down block (30) and which can be moved in the longitudinal axis (A) of the ingot mould (10) either individually or together by a regulating arrangement.
10. Device according to claim 9, characterised by two current sources (36, 36a), one of which is connected to the consumable electrode (28), wherein the other current source (36a) is connected both to the consumable electrode and to the current-conducting element (18a).
11. Device according to claim 10, characterised by two current sources (36, 36a) which can be regulated independently of one another.
12. Device according to one of claims 9 to 11, characterised in that in each case one supply (32) for the consumable electrode (28) and a further supply (32a) for the current-conducting element (18) is led from the current source (36), or in that returns (34, 35) lead from the base plate (14) and the current-conducting element (18) to the current source (36).
13. Device according to one of claims 9 to 12, characterised in that several current-conducting elements (18, 18a) separated by insulating elements (16b) are arranged in a zone of the ingot mould (10).
14. Device according to claim 13, characterised in that the current-conducting elements (18, 18a) with the insulating elements (16b) form a ring, wherein optionally two current-conducting elements (18, 18a) are present, of which one is connected to the supply (42a) and one is connected to the return (35).
15. Device according to one of claims 9 to 14, characterised in that the division of the current intensities between the individual supplies or returns (32, 32a; 35) can be adjusted by regulatable resistances (42, 42a; 44, 44a).
16. Device according to one of claims 9 to 15, characterised by rectifier stations as current source/s (36, 36a), the polarity of which is designed to be reversible.

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