DE2918757C2 - Electrode for electric arc furnaces - Google Patents

Description

Electrode sections reduce the risk of fluid leakage exclude, ils is evident. ti; iU too the nipple is cooled evenly to a particularly high degree, so that high thermal loads and Deformations of the nipple are excluded, so that the nipple can also be reused for a long time and can be easily connected to or loosened from the electrode sections.

In an expedient embodiment, the flow pipe ends at an axial distance from the closed one lower end of the nipple, the open upper end of which encloses the protruding flow pipe with a radial spacing There are then no special outlet openings at the lower end of the flow pipe, with the cooling liquid passed in an advantageous manner to the thermally most stressed lower end of the nipple will. Any additional measures to guide the coolant inside the nipple can omitted.

An exemplary embodiment of the invention is explained in more detail below with reference to a schematic drawing, where iz for better understanding first the known and then the improved according to the invention Training is dealt with.

F i g. 1 shows a composite electrode in perspective Depiction;

Fig.2 is an enlarged longitudinal section through the Electrode in the known design;

FIG. 3 shows in a manner corresponding to the representation in FIG Partial section the training according to the invention;

F i g. 4 shows the nipple detached from the upper electrode section together in a perspective illustration with a tool used to connect and disconnect.

According to FIG. 1, the composite electrode 10 includes a top metallic portion 12 and 12 a lower consumption section 14. At the connection point 15 is a device for fixed connection of the two sections provided together. This connecting device will be described in detail later. An electrode clip 16 of known type is provided which has a support arm 18 extending therefrom extends from a known type of control device, not shown, to the electrode terminal 16. As Usually the electrical current is along arm 18 and through clamp 16 to the composite electrode 10 applied. The known control device, not shown, regulates the vertical height of the composite electrode 10 to the most favorable in accordance with previous practice To achieve arc ratio Fe.

At the top of section 12, two cooling water lines 19 and 20 are provided through which cooling water the upper section 12 is fed or discharged.

The composite electrode 10 shown in Fig. 1 is down through an opening in the roof or in the top wall of an electric arc furnace of the standard design introduced, the roof opening in known Way is sealed against the escape of gases. These parts are known and therefore not shown.

The upper or metallic section 12 of the composite, shown in detail in FIG Electrode 10 can be made of iron or an iron alloy. It has a cylindrical outer wall and a cylindrical inner wall 24 which is concentric and spaced inwardly from the outer wall 22 arranged Lsi, wodiiri-h a channel 2h of ring shaped cross-section is formed between the two walls. The channel 26 is an upward branch of the line a cooling water circulation within the metallic portion 12 of the composite Electrode 10 is provided.

Across the top of both walls 22 and 24 extends a circular top wall 28 which is so is dimensioned so that it extends beyond the outer surface of the outer wall 22, as is evident from both figures can be seen.

A first transversely extending partition wall 30 is spaced below the top wall 28 and extends only within the inner wall 24 to which it is welded. Above the partition wall 30, the inner wall 24 is provided with several openings 31 so that the cooling water flowing upwards through the annular channel 26 can easily and without great flow resistance reach an opening 33 which is connected to an outlet connection M which extends from the upper end the outer wall 22 extends radially outward

Another partition 36 is provided near the lower end of section 12. Also this partition 3C- extends only within the perimeter of the inner wall 24 to which it is welded.

A central axial tube 37 extends downwardly through the top wall 28 and the partition wall 30 and terminates at a central opening 38 in the partition 36, so that water through the pipe 37 down into the Area below the partition 36 can flow.

At the lower end of the outer wall 22, a component 40 is provided which is designed to be radially symmetrical and an annular upwardly open channel 42 defined between an outer cylindrical Wall 43, a lower annular wall 45 and an inner frustoconical wall 46 is formed. A circular plate extends across the upper open end of the inner conical-uimp-shaped wall 36 48. The bounded by the annular channel 42, the plate 48 and the partition wall 36 forms an im essential circular disc-shaped channel with a downwardly protruding circumferential section, which serves to Cooling liquid from the lower end of the P.ohr 37 radially outward to the lower end of the annular channel 26 lead. As can be seen from Fig.2, extends the inner wall 24 down into the annular channel 42, thereby forcing the cooling water, to flow continuously along the inner surface of the component 40, whereby a uniform cooling of the Component 40 is guaranteed. If the inner wall 24 did not extend down into the channel 42, there would be a risk that the water at the lower end of the channel 42 would not participate in the overturning flow, will overheat and vaporize, which could cause an explosion.

In the lower end of the annular channel 26 are several guide vanes extending in the longitudinal direction 47 arranged to reduce the turbulence as much as possible and a laminar. Flow of the coolant through the channel 26 should favor.

The upper end of the outer wall 22 is welded to an annular flange 50 which is the same outside diameter like the top wall 28 has. The annular flange 50 and the top wall 28 are bolted 52 clamped to one another, with a seal between the annular flange 50 and the upper wall 28

is arranged around the upper end of the annular Channel 26 to seal. As can be seen, there is no permanent supporting connection between the inner Wall 26 (with the partitions 30,36 and the central tube 37) and the outer wall 22 (with the lower Component 40). It is advantageous to be able to remove the entire inner part from the outer part of the upper section 12 in order to carry out maintenance work, inspections and the like. For this reason, the Riügflansch 50 was provided, the only connection point between the two parts on Upper end is found by means of the screw bolts 52, and at the lower end only the guide vanes 47 a cause radial support.

A T-shaped coupling piece 54 is screwed onto the upper end of the central tube 37 and a water inlet pipe 56 is connected to the coupling piece 54,! N the other opening of the T-shaped Kunnliinp-sstttcks 54> * (pin Sichprheiisko ⁿ i 57 of known construction screwed in.

At the lower end of the section 12, the inner surface of the frustoconical wall 46 is provided with threads which are connected to the threads of a Let graphite nipple 59 screwed, which is of the type that has been used so far for connecting two Graphite cylinders is used together. The consumed graphite electrode also has one with Threaded receiving recess 60 at its upper end in order to receive the other end of the screw nipple 59 penetrating on both sides.

Especially from FIG. 2 it can be seen that the diameter of the consumable graphite section 14 of the composite electrode 10 has a smaller diameter than the upper portion 12. So far are the electrodes are usually somewhat oversized for reasons of mechanical strength, so it is the Diameter of the electrodes slightly larger than the electrical requirements make it necessary. In the however, the diameter of the graphite portion of the composite electrode can be reduced to the minimum required for considerations other than mechanical strength because the upper end of the graphite portion 14 can be reduced in diameter because of the contact with the water-cooled metallic portion 12 is cooled, thereby increasing the extent is reduced in that the graphite material oxidizes away on its surface. Accordingly, the initial strength of the connection between maintain the two sections. Furthermore, it is not necessary to meet high requirements for the surface properties of the graphite section 14 in order to produce a good electrical connection.

In the electrode shown, the terminal 16 is arranged directly on the upper metallic section 12, so that there is a metal-to-metal contact with excellent electrical conductivity

By keeping the greater part of the interior of the upper section 12 free of water, the weight of the entire electrode can be reduced to a minimum. In the case of the in FIG. The construction shown in FIG. 2 can take the total weight of the upper one Section on a weight less than the weight of a conventional CiniphiieloklriHli. · The same diameter Who! lh-r; ih); i-srl / l witiIimi. D.uliircli becomes ibs (li-wicll! lowered that of the Klekirodciimasi. to which the Ann 18 is assigned, must raise, and this increases the cost maintenance is reduced while the lifting speed increases at the same time.

The junction where the consumable portion and the non-consumable portion of the composite electrode join together can be arranged at a lower point of the electrode as a whole than at the bottom Connection is the case with the known electrodes. Therefore, accidental scrap holes or furnace movements, which lead to a force acting on the side of the electrode, produce a lower bending load in the connection due to the smaller moment arm area, which reduces the risk of breakage. Furthermore, any break at the junction means a smaller loss of electrode weight because of the Connection point is arranged lower or more to the electrode tip.

It is advisable to design the water-cooled section with a female shape so that any thermal expansion of the lower section and connecting pin that occurs becomes a denser one

Connection rather than loosening.

The residual volume within the upper metallic portion 12 of the composite electrode 10 is completely sealed against the above-described liquid flow, it being provided that

this residual volume contains only air. In order to avoid changes in the air pressure in this residual volume as a result of heating, a connecting line 67 is provided vorgesei in, which extends through the partition wall 30 and through the top wall 28 extends.

The training according to FIG. 3 and 4 largely corresponds to the training described above. The corresponding parts are therefore given the same reference numerals provided with a distinctive line. Deviations are only indicated at the lower end of the

Metallic upper electrode section 12 'as well as the double-conical screw nipple 59' is provided. So the circular plate 48 is absent at the lower end of the electrode section 12 '. Instead, he goes himself upwardly tapering incision from the with Screw-threaded frustoconical Wall 46 'is surrounded, directly by means of a bottom opening into the interior of the electrode section 12'. However, the partition wall 36 'prevents a connection with the air space within the inner jacket 24'.

The main difference compared to the embodiment according to Figure 2 concerns the internal construction of the Screw nipple 59 '. This is no longer made of graphite, but is made of a metal such as copper or steel.

The screw nipple 59 has a central cavity 65 and is designed with an open upper enue 66, while the lower end 67 is closed. The central axial tube 37 'extends further downward than the tube 37 according to FIG. As shown in FIG. 3, the tube 37 'extends axially downward into the cavity 65 of the nipple 59'. When cooling liquid is thus conveyed down through the central tube 37 ', the cooling liquid flows through a section which extends from the lower end of the central tube 37' up through the nipple cavity 65 and through the open upper end 66 of the nipple 59 'from this extends out, whereupon the cooling liquid radially outwards and downwards to the lower end of the Kiijj-.kiiiiiils h / w. Uiickl; iiifk, in; ils / wischen ilrin Aitlli-ii

ti manle! 22 ^ and the inner jacket 24 'of the upper lilcktrodenabschnitts 12' flows

The screw nipple S9 ⁷ has at its lower end 67 two diametrically opposite bores

70, which can receive projecting pins 72 of a hand-operated tool 74 that is used for sealing Screwing or tightening the screw nipple 59 into the wall 46 'of the frustoconical wall Surrounded incision at the lower end of the electrode portion 12 'is used.

In experiments it was found that cooling in the connecting area between the consumable bottom portion and the metallic upper portion is particularly good, and thereby a Seitenab- \ o brand of the lower graphite portion to a more distant from its upper end region is limited. Furthermore, the junction between the two electrode sections remains essentially cold, and accordingly the sections can be easily detached from the nipple so that a used graphite section can be replaced.

For this purpose 2 sheets of drawings

30th

35

40

45

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65

Claims (2)

Patent claims: 1. Electrode for electric arc furnace, consisting of an upper section made of metal and a replaceable lower section of consumable Material that are substantially cylindrical in shape and connected by a screw nipple are connected, the upper portion enclosing a cavity open at the upper end and a liquid cooling device with a flow channel and a return channel, extending from the top of the section extend essentially the entire length of the section and extend at the lower end of the section through an in particular the electrode cross section essentially completely filling radial channel with adjoining flow guide vanes are connected to each other, the Vorlaufkaftai of one extending through the upper section extending central tube is formed, the return channel with the Radtal channel directly connected annular channel between an outer jacket and an inner jacket of the upper section and the cavity, which is open at its upper end, is annular between the inner jacket and the central tube is formed thereby characterized in that the upper electrode portion (12 ') at its lower end one with the Radial channel communicating bottom opening has, daL 'the nipple (59') is metallic and hollow and has an open top end («») through which through the nipple cavity (65) is in communication with the radial channel, lind d'Ö the central flow pipe (37 ') protrudes with its lower end into the nipple cavity (65) 2. Electrode according to claim 1, characterized in that the flow pipe (37 ') with an axial distance ends from the closed lower end (67) of the nipple (59 '), the open upper end (66) of which the enclosing protruding flow pipe (37 ') with radial spacing 45 The invention relates to an electrode for an electric arc furnace, consisting of an upper section made of metal and a replaceable lower section of consumable Material having a substantially cylindrical shape and through a screw nipple are connected to one another, the upper section enclosing a cavity which is open at the upper end and a liquid cooling device having a flow channel and a return channel leading from the Starting at the upper end of the section, extend over substantially the entire length of the section and at the lower end of the section through an in particular the electrode cross-section essentially Connect the completely filling radial duct the stretcher lite wings are connected to each other, the flow channel of one extending through the upper one Section extending central tube is formed. the return channel one with the radial channel directly connected ring channel / between an outer jacket M and an inner sleeve of the upper section is and the hollow space, which is open at its upper end, is annular / between the inner diameter and the central tube is trained Such an electrode, including the radial channel and the flow guide vanes, is already known (DE-OS 27 39 483). This is advantageously done with a non-consumable, reusable upper Electrode section worked, the cross section of which remains unchanged so that the seal of the compensation for the electrode consumption axially displaceable electrode at its upper end no special Raising problems Furthermore, the cooling device produces a good effect, in particular across the electrode cross-section seen substantially uniform cooling of the upper electrode portion, so that the thermal Stresses are reduced to a bearable level and by forced circulation without standing liquid is countered the risk of it by sudden evaporation of liquid in the upper Electrode section can be damaged and malfunction. However, it has been shown that, despite the advantages achieved, the Kühiverhähnisse at the lower end of the upper Electrode section or in the connection area between the two electrode sections, where the thermal stress is particularly great, not all requirements are met in particular in the known design of the double-conical screw nipple, half of which in the upper and to the Half screwed into the lower electrode section and like the latter is made of graphite, not cooled Therefore, overheating and deformation may occur of the screw nipple, causing a loosening or connecting with respect to the electrode sections difficult. In an electrode of a similar type (US-PS 25 99 179) a hollow screw nipple is present, which extends in the longitudinal direction is flowed through by cooling water. The invention is based on the object of providing the cooling device for the electrode mentioned at the beginning improve that also the one enclosed between the two electrode sections and therefore heavy accessible nipple and thus the connection area between the two electrode sections is cooled without the risk of possibly explosive liquid evaporation must be taken. This object is achieved according to the invention in that the upper electrode section at its lower End has a communicating with the radial channel bottom opening that the nipple is metallic and is hollow and has an open upper end through which the nipple cavity with the radial channel in Connection is, and that the central flow pipe protrudes with its lower end into the nipple cavity. In this way, the cooling water, which is still essentially at the low flow temperature, is removed or other coolant introduced directly into the nipple, which is thereby particularly well cooled. Included it is achieved in a particularly simple, expedient manner that the cooling liquid is centrally located at the lower end of the nipple cavity and from there through the annular space / wipe the outer unifnng of the protruding flow pipe and the cavity wall of the nipple rises, the comparatively low Distance / wipe these boundary walls of the Nippclkanals to a comparatively high flow velocity lead, despite the temperatures occurring in the connection area between the two