EP0149768A1 - Liquid-cooled holder element of a composite electrode for electric arc furnace - Google Patents

Abstract

In the case of a liquid-cooled support piece (1) of a combination electrode (2) of an arc furnace, a shut-off device (14) biased in the blocking direction for the cooling medium is arranged in the flow path (13) with an actuating element (15), by means of which an exchangeable lower part, which is subject to erosion, is screwed on (2) the combination electrode, the shut-off device (14) is set against the bias in the open state. If the lower part breaks in the area of the nipple (5), the flow path (13) is blocked by releasing the actuator (15). Additional protection of the threaded nipple is achieved by means of a protective cap screwed onto the threaded nipple with an external thread corresponding to the internal thread of the lower part (2).

Description

The invention relates to a cylindrical support piece of a combination electrode according to the preamble of claim 1.

In the case of this type of support, which has become known from EP-B1-0010 305, a threaded part or a nipple for screwing on an exchangeable lower part made of graphite, which is subject to erosion, is fastened at the lower end. The threaded part has channels for the cooling medium, which are fed with the cooling medium via the cooling system of the support piece. In one embodiment of the known holder, the cooling system guiding the electrode current and the cooling liquid comprises an inner metal tube inserted into an outer metal tube at a distance, the annular space between the two tubes in the lower region of the support piece being connected to the interior of the inner metal tube. The cooling medium, generally water, is fed via a connection to the interior of the inner metal tube above the clamping point of the support piece, down into the area of the threaded part and returned there into the annular space between the two metal pipes, which is one above the clamping point in the electrode arm contains another connection for the outlet of the cooling water. Outside of the support piece, a device for measuring the cooling water quantity is installed in the cooling water supply or in the cooling water return, which provides an alarm signal when the flow rate is below the prescribed, which can be used to pull the support piece upwards via the electrode setting system.

When using a combination electrode with a supporting piece of this type in an arc furnace in which scrap is melted, mechanical stresses can result in the exchangeable lower part in the area of the threaded part or nipple breaks and then the combination electrode is moved further downward by the electrode setting system, which as a rule leads to damage to the now no longer protected lower tip of the support piece and possibly to an escape of the coolant.

The invention has for its object to provide a support piece of the type mentioned in the preamble of claim 1 with a signaling device that provides a signal in the event of a break in the replaceable lower part in the area of the threaded part or nipple, which can be used to raise the support piece. In addition, in this case, the inflow of the cooling medium should be able to be interrupted immediately in order to keep the emerging quantity of cooling medium as small as possible in the event of damage to the lower tip of the support piece.

In addition, if the replaceable lower part breaks in the area mentioned, the threaded part is to be protected from damage and the maintenance work required for the support piece is to be reduced considerably.

The invention is characterized by the features of claims 1 and 13, respectively. Advantageous refinements of the invention can be found in the remaining claims.

According to one aspect of the invention, in the support piece of the combination electrode in the flow path of the coolant, a locking device biased in the blocking direction with an actuating element is arranged, by means of which the locking device can be set against the bias in the open state when an exchangeable lower part is screwed onto the threaded part. The flow path is thus blocked when the lower part is removed and opened when the lower part is screwed on. If the lower part of an electric If the broken part is removed by force from the threaded part or nipple, the flow path is immediately blocked due to the pretensioning of the shut-off device, i.e. the flow of the cooling medium is suddenly interrupted and this switching process has an immediate effect at any point on the flow path in the case of an incompressible cooling medium such as water and can thus be used as a signal for the electrode break and a control signal for the electrode control system. This eliminates the need for additional cables or lines for an alarm system. Preferably, the shut-off device is arranged in the flow path of the flow to the lower tip of the support piece and a flow meter detecting the locked state of the shut-off device in the flow to this support piece, so that if the unprotected tip is damaged after an electrode breakage and the cooling medium escapes, not only that at this point Notification system remains intact, but also the flow of the cooling medium to the damaged area is interrupted. The shut-off device thus fulfills two tasks, on the one hand it is a signal transmitter for the flow meter arranged in the flow, which in turn emits a control signal to the electrode actuating system, and on the other hand it is a closure element which interrupts the inflow of the cooling medium to the damaged point on the tip of the support piece. In this way, the cooling medium contained in the flow path to the shut-off device can be retained and prevented from escaping into the furnace.

According to a further aspect of the invention, the threaded part or. the threaded nipple, onto which the lower part of the combination electrode is screwed, is protected by a protective cap, preferably made of graphite, which has an external thread onto which the lower part can be screwed. The protective cap then forms an intermediate piece, which in the event of a break in the lower part in the area of the threaded nipple remains on it and protects the threaded nipple from damage by arcing. The damaged protective cap can be replaced quickly and easily by unscrewing the threaded nipple of the support piece. This is an inexpensive element that can also be screwed onto already existing liquid-cooled support pieces in the case of conical threaded nipples. The two aspects of the invention mentioned are preferably combined, that is to say in addition to the protective cap, the shut-off device described in this application is also provided. Here, the protective cap and, if necessary, the shut-off device are to be modified such that the conditions specified in claim 1 are met.

• Fig. 1 einen Teil des Längsschnittes eines flüssigkeitsgekühlten Tragstückes mit aufgeschraubtem Unterteil einer Kombielektrode;
• Fig. 2 den Schnitt II-II und
• Fig. 3 den Schnitt III-III von Fig. 1;
• Fig. 4 ausschnittsweise das Gewindeteil eines flüssigkeitsgekühlten Tragstückes mit aufgeschraubter Schutzkappe von unten;
• Fig. 5 im Längsschnitt einen Teil des Gewindeteils des Tragstückes und der aufgeschraubten Schutzkappe;
• Fig. 6 die am Gewindeteil anliegende Stirnseite der in Fig. 5 dargestellten Hülse;
• Fig. 7 die Hälfte einer Schutzkappe im Längsschnitt;
• Fig. 8 eine der Fig. 5 entsprechende Ansicht mit einem Betätigungsglied entsprechend Fig. 1.

The invention is explained in more detail by three exemplary embodiments with reference to 8 figures. Show it

• 1 shows a part of the longitudinal section of a liquid-cooled support piece with a screwed-on lower part of a combination electrode;
• Fig. 2 shows the section II-II and
• Fig. 3 shows the section III-III of Fig. 1;
• 4 shows a section of the threaded part of a liquid-cooled support piece with a screwed-on protective cap from below;
• 5 shows in longitudinal section a part of the threaded part of the support piece and the screwed-on protective cap;
• FIG. 6 shows the end face of the sleeve shown in FIG. 5 resting on the threaded part;
• 7 shows half of a protective cap in longitudinal section;
• 8 is a view corresponding to FIG. 5 with an actuator corresponding to FIG. 1.

The liquid-cooled support shown in Fig. 1 for a burnable, replaceable sub Part 2 of a combination electrode of an arc furnace contains an exposed outer metal tube 3, the upper section of which has approximately the same diameter as the lower part 2 and can be clamped in an electrode support arm of an arc furnace. At the opposite end to the clamping point, ie at the lower end, the metal pipe 3 has a flange 4 and a threaded part 5 for screwing on the lower part 2. The diameter of the lower section of the metal pipe 3 which dips into the furnace space during operation is reduced compared to the diameter of the lower part 2.

An inner metal tube 6 is provided at a distance from the outer metal tube 3. The cavity 7 of the inner metal tube serves as a channel for the supply of the cooling medium, preferably cooling water, to the liquid-cooled threaded part 5. The cooling water is returned via the space 8 between the outer and the inner metal tube. At the upper end of the liquid-cooled support piece 1, the cavity 7 is connected to a connection for the supply line (flow) and the intermediate space 8 is connected to a connection for the return (return) of the cooling medium.

The electrode current is introduced into the upper section of the outer metal tube 3, conducted downwards in the metal tube made of steel, and passes through the threaded part 5 made of electrolytic copper into the nippled lower part 2.

A number of inner bores 9 and a number of outer bores 10 are provided in the flange 4. The holes 9 are distributed on a circle around the central axis of the support piece 1 and are connected to the cavity 7, the holes 10 are also distributed on a larger diameter circle around the central axis and are connected to the space 8. The bores serve as channels for the supply and discharge of the cooling liquid to the channel 12 delimited by an annular displacement body 11 in the threaded part 5. The flow path for the cooling liquid is indicated by arrows 13.

According to the invention, a shut-off device 14 biased in the blocking direction with an actuating member 15 is arranged in the flow path 13. When the lower part 2 is screwed onto the threaded part 5, the flow path 13 is opened by the actuating member 15, and when the lower part 2 is removed, the flow path is blocked. For this purpose, in the locked state of the shut-off device 14, the actuating member 15 protrudes from the threaded part 5, as indicated by the dash-dotted position 16 in FIG. 1, into an area which is taken up by an area of this lower part when the lower part is screwed on. It is essential that when the lower part 2 is screwed on by any area of this lower part or a part applied to this lower part, the actuating member 15 is actuated against the pretension of the shut-off device, and as a result the flow path 13 is released.

A preferred embodiment of the shut-off device is described in detail below.

The actuator 15 of the shut-off device 14 is designed as a rod which is guided within a sleeve 17 which is fastened coaxially in the flange 4 and in the threaded part 5, in the present case welded to these parts. With the exception of the lower section, the sleeve 17 surrounds the actuator 15 at a distance, so that an annular channel 18 for the cooling liquid is formed between the actuator and the sleeve. This is connected to channel 12 by channels 19. The In this way, flow path 13 receives a branch 13a. Good cooling of the actuating member 15 can be achieved via this secondary path. The actuation member 15 is guided on the one hand by the lower section of the sleeve 17, in which ring seals 20 are present to prevent the coolant from escaping, and by a guide element 21 which is inserted into the sleeve 17 and which has the shape shown in FIG. 3 .

The actuator 15 carries at the upper end a welded plate-shaped shut-off body 22 which, when the lower part 2 is removed and the actuator 15 assumes the position 16 shown in broken lines, closes the inner bores 9 and the annular channel 18 of the sleeve 17 in the position 23 also shown in broken lines and thus blocks the flow path 13. The blocking takes place with the lower part 2 removed by a pretension which is brought about on the one hand by the liquid pressure in the cavity 7 of the inner metal tube 6 and on the other hand by a compression spring 24 which is supported against a holder 25. The holder 25, the shape of which can be seen in FIG. 2, is fastened in the lower section of the inner metal tube 6, welded in the present case, and carries a guide pin 26 for the compression spring 24. This presses on the plate-shaped shut-off body 22 and is here also by a screwed pin 27 out. The lower end of the actuator, which is directly exposed to the furnace atmosphere in the event of an electrode break, is designed to be easily replaceable. In the present case, it consists of a screwed-on end piece 28.

In the operating state, the shut-off device assumes the position shown in solid lines in FIG. 1. In the event of an electrode breakage, ie a breakage of the lower part 2, which is preferably made of graphite, in the area of the nipple, the actuating member 15 is released and the plate-shaped shut-off body 22 together with the actuating member 15 is pressed down by the liquid pressure in the cavity 10 and by the spring force of the compression spring 24 thereby the inflow to the inner bores 9 and to the annular channel 18 is suddenly interrupted. In the case of an incompressible cooling medium, such as water, this switching operation is registered in advance by a monitoring device with practically no time delay and a control signal is delivered to the electrode positioning system, which immediately pulls the relevant support piece upwards. If the threaded part 15 is damaged as a result of the electrode breakage, the liquid in the cavity 7 is prevented from escaping by the plate-shaped shut-off body 22.

Of the rod-shaped, liquid-cooled support piece with a threaded nipple 101 for screwing on the replaceable lower part of a combination electrode, only the threaded nipple is shown in FIG. 5. In the present case, it consists of copper and, as in the first exemplary embodiment, is welded to the lower end of the support piece, which contains a metallic cooling system that conducts the electrode current. The threaded nipple 101, also not shown, has channels for the cooling medium which are fed via the cooling system of the support piece. It is conical in the usual way and provided with an external thread corresponding to the internal thread of the exchangeable lower part of the combination electrode.

A protective cap 102 made of graphite or a refractory material is screwed onto the threaded nipple 101 and, for this purpose, has an internal thread corresponding to the external thread of the threaded nipple 101, ie an internal thread of the lower part to be screwed onto the nipple 101 has an identical thread. The threaded connection is designated 103.

The protective cap 102 is conical in the same way as the threaded nipple 101 and is provided on its outer surface with an external thread 104 which corresponds to the internal thread of the lower part of the combination electrode to be screwed onto the protective cap 102. A rotation lock 105 is provided between the protective cap 102 and the threaded nipple 101.

The rotation lock 105 is realized in this embodiment in that there are two eccentrically and diametrically arranged through holes 106 in the bottom of the protective cap 102 and in the end face of the threaded nipple 101 there are two correspondingly arranged threaded holes 107, into each of which a screw 108 is screwed. The screw head of the screw 108 is supported by a washer 109 on a shoulder 110 of a sleeve 111, which is preferably made of refractory material and whose outer diameter is adapted to the diameter of the through hole 106. 4 and 6, the sleeve 111 has an elongated hole 112 which is stepped in the axial direction of the sleeve 111 and thus forms the shoulder 110. Tolerances of the threaded connection 103 can be compensated for by the elongated hole. To improve the adhesive bond between the sleeve 111 and the end face of the threaded nipple 101, the end face of the sleeve 111 bearing against this end face is provided with grooves 113 (see FIG. 6). The sleeve 111 and the screw 108 are recessed in the bottom 116 of the protective cap 102 and are thus protected in the event of an electrode break. The cavity between the countersunk screw 108 and the outer end face 114 of the protective cap 102 is filled with refractory ramming paste 115. In order to achieve a higher break resistance of the protective cap 102, the external thread 104 is turned in the area of the bottom 116 up to the beginning of the internal thread, ie a thread-free section 117 is formed. In the operating state, the lower part of the combination electrode is screwed onto the external thread 104 of the protective cap 102.

If the protective cap 102 is damaged after an electrode break in the area of the threaded nipple, the damaged protective cap 102 is replaced by a new protective cap as follows.

First the two screws 108 and the sleeves 111 are removed and then the damaged protective cap is unscrewed with a key which has two pins which fit into the through holes 106. A new protective cap 102 is then screwed onto the threaded nipple 101 using the key. In this position, the threaded bores 107 lie in the area of the through holes 106, so that after the sleeves 111 have been inserted, the screws 108 are screwed in and the rotation lock can thus be produced. After screwing a new lower part of the combination electrode onto the protective cap 102, the fault is eliminated.

7 shows in longitudinal section one half of the protective cap 102 already described.

The protective cap is preferably provided in connection with the shut-off device described with reference to FIGS. 1 to 3. For this purpose, the protective cap and, if applicable, the shut-off device are modified such that the shut-off device can be moved into the open state when the lower part is screwed onto the protective cap. Fig. 8 shows a corresponding training. After that a bore 118 is provided in a protective cap 102a, through which an end piece 28a screwed onto the actuating member 15a of the shut-off device 14 (see FIG. 1) is guided and in the illustrated closed position of the shut-off device protrudes from the lower end face of the protective cap 102a. When screwing the bottom part 2 (see Fig. 1) of the _K ombielektrode the actuator 15a is pushed upward and the cooling circuit are free. If the lower part breaks in the area of the protective cap 102a, the nipple 101a is protected, and if the protective cap 102a and the end piece 28a are damaged, these parts can be replaced quickly and easily.

Claims (18)

1. Attachable to the electrode support arm of an arc furnace, cylindrical support piece (1) of a combination electrode which contains a flow path (13) for a cooling medium and at the lower end carries a threaded part (5) for screwing on a replaceable lower part (2) of the combination electrode which is subject to erosion , characterized in that in the flow path (13) a locking device (14) biased in the blocking direction is arranged with an actuating member (15), by which when the lower part (2) is screwed onto the threaded part (5) the locking device (14) counter to the pretension can be put in the open state. 2. Carrier according to claim 1, characterized in that the actuating member (15) in the locked state of the shut-off device (14) protrudes from the threaded part (5) into an area which is taken up by an area of the lower part (2) when the lower part (2) is screwed on becomes. 3. Carrier piece according to claim 2, characterized in that the shut-off device (14) contains an axially displaceable rod as an actuator (15) which carries at one end a in the flow path (13) arranged shut-off body (22) and with the other end of the Front of the threaded part (5) protrudes. 4. Support piece according to claim 3, characterized in that the actuating member (15) within a channel (18, 19) provided for the cooling medium sleeve (17) is guided. 5. Support piece according to one of claims 1 to 4, characterized in that it has in the lower section in the flow path (13) of the cooling medium has a flange (4) penetrated by at least one channel (9) and the channel can be closed by the shut-off device (14) is. 6. Support piece according to claim 5, characterized in that the flange (4) has a plurality of channels (9) which can be closed by a plate-shaped shut-off body (22). 7. Support piece according to one of claims 1 to 6, characterized in that the shut-off device (14) is biased by a spring (24). 8. Support piece according to one of claims 1 to 7, characterized in that the shut-off device (14) is biased by the pressure of the cooling medium. 9. Support piece according to one of claims 1 to 8, characterized in that the threaded part (5) contains a channel (12) for the cooling medium, which lies in the flow path (13) of this medium. 10. Support piece according to one of claims 5 to 9, characterized in that the sleeve (17) is fastened coaxially in the flange (4) and in the threaded part (5). 11. Support piece according to claim 9 or 10, characterized in that it contains an inner and spaced therefrom an outer metal tube (6 or 3), which are closed and connected by the flange (4) in the lower section, which in the cavity (7) of the inner metal tube (6) and in the space (8) between the two metal tubes (6 and 13) opening channels (9 and 10), which with the channel (12) and the channels (18, 19th ) are connected in the threaded part and that the support piece has at the upper end a connection for the cooling medium which is connected to the cavity (7) of the inner metal tube (6) and a connection which is connected to the intermediate space (8) between the two metal tubes ( 6 and 3) is connected. 12. Carrier piece according to one of claims 1 to 11, characterized in that a protective cap (102a) screwed onto the threaded part (101a) with an external thread (104) corresponding to the internal thread of the lower part to be screwed on (2) and a rotation lock (105) between the protective cap (102a) and the threaded part (101a) is provided and that the shut-off device (14) can be moved into the open state when the lower part (2) is screwed onto the protective cap (102a). 13. Attachable to the electrode support arm of an arc furnace, cylindrical support piece (1) of a combination electrode which contains a flow path (13) for a cooling medium and at the lower end carries a threaded part (5) for screwing on an exchangeable lower part (2) of the combination electrode which is subject to erosion , characterized by a protective cap (102) screwed onto the threaded part (101) with a cap corresponding to the internal thread of the lower part to be screwed on External thread (104) and a rotation lock (105) between the protective cap (102) and the threaded part (101). 14. Carrier piece according to claim 12 or 13, characterized in that the outside of the protective cap (102) in the region of the bottom (116) has a thread-free section (117). 15. Support piece according to one of claims 12 to 14, characterized in that the threaded part (101) and the protective cap (102) are conical. 16. Support according to one of claims 12 to 15, characterized in that the protective cap (102) by at least one eccentrically inserted into the end face of the threaded part (101), in the bottom (116) of the protective cap (102) countersunk screw (108) Rotation is secured. 17. Carrier according to claim 16, characterized in that in the bottom (116) of the protective cap (102) at least one eccentrically arranged through hole (106) is provided, in which an outer diameter adapted to the diameter of the through hole sleeve (111, 111 ¹ ) an elongated hole (112) is used as an intermediate piece between the head of the screw (108) and the end face of the threaded part (101). 18. Support piece according to one of claims 12 to 17, characterized in that the protective cap (102) consists of graphite.

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