DE2918757A1 - ELECTRODE FOR ARC FURNACE - Google Patents

Description

PATENT LAWYERS.

WUESTHOFF - ν. PECHMANN- BEHRENS

professional representatives before the european patent office agrees pres l'office europeen des brevets

DR.-LNG. FRANZ WUESTHOFF

Dfc.-PHIL ·. FREDA WUESTHOFF (1927-I9J6) D1PL.-ING. GERHARD PULS (1952-1971) DIPL.-CHEM. DR. E. BARBER OF PECHMANN DR.-ING. DIETER BEHRENS DIPL.-ING .; DIFL.-TIRTSCH.-ING. RUPEXT GOETZ

29187b? D-8000 MUNICH SCHWEIGERSTRASSE phone: (089) 66ίο ji TELEGRAM: PROTECTPATENT TELEX! J 24 070

51 908

Patent application: (Addition to patent. ■ ... ... = P 27 39 483.8-34 =)

Applicant: The Steel Company of Canada, Limited Stelco Tower, 100 King Street West, Hamilton, Ontario LSN 3T1, Canada

Title:

Electrode for electric arc furnace

909847/9708

PATENT LAWYERS:; ; ; :

WUESTHOFF - ν. PECHMANN - BEHKXNS - GOETZ

PROFESSIONAL REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE MANDATAIRES AGREiS PRES l'OFFICE EUROPEEN DES BREVETS

. DC-ING. FRANZ WUESTHOFF toR.raiL. FREDA VUESTHOFF (1927-1956) DUU.7-ING. GERHARD PULS (1952-1971) DIPL.-CHEM. DR. E. BARBER OF PECHMANN DR.-ING. DIETER BEHRENS DIPL.-ING .; DIPL.-WIRTSCH.-ING. RUPERT GOET

D-8000 MUNICH 90 SCHWEIGERSTRASSE 2

phone: (089) 66 20 ji telegram! protectpatent telex: 524070

51 908

Description:

Electrode for electric arc furnace.

The invention relates to an electrode for an electric arc furnace, consisting of a top section made of metal and a replaceable lower section made of consumable material, the Have a substantially cylindrical shape and are connected to one another by a screw nipple or the like, wherein the upper section encloses a cavity open at the upper end and a liquid cooling device with a flow channel and a return channel leading from the upper end of the section extend substantially the entire length of the section and at the lower end of the section in particular by a radial channel which essentially completely fills the electrode cross-section with a subsequent radial channel Flow guide vanes are connected to one another, the flow channel from one extending through the upper portion central tube is formed, the return channel is an 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 one Tube is formed.

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Such an electrode, including the radial channel and the flow guide vanes, is already known (DE-OS 27 39 483). It is advantageously used with a non-consuming reusable upper electrode section worked, the cross-section of which remains unchanged, so that the Sealing of the electrode, which can be axially displaced to compensate for the electrode consumption, at its upper end is not special Poses problems. Furthermore, the cooling device brings about a good and in particular seen over the electrode cross-section essentially uniform cooling of the upper electrode section, so that the thermal stresses are reduced to a bearable level and by forced circulation without standing liquid the risk of it being met by sudden evaporation of liquid in the upper part Electrode section to damage and operational malfunctions comes.

However, it has been shown that despite the advantages achieved the cooling conditions 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 high is large, does not yet meet all requirements. In particular, in the known design, the double-conical. Screw nipple that is half screwed into the upper and half into the lower electrode section and like the latter is made of graphite, not cooled. This can lead to overheating and deformation of the screw nipple, which makes it difficult to detach or connect with respect to the electrode sections.

The invention is accordingly based on the object, the To improve known cooling device so that the enclosed between the two electrode sections and thereby nipples that are difficult to access and thus the connection area between the two electrode sections are effectively cooled without the risk of potentially explosive liquid evaporation being accepted got to.

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According to the invention, this object is achieved in that the upper electrode section at its lower end has a bottom opening communicating with the return channel comprises that the nipple is metallic and hollow and has an .open top end through which the nipple cavity is in communication with the return channel, and that the central flow pipe with its lower end into the Protruding nipple cavity.

In this way, the cooling water or other water that is essentially still at the low flow temperature is removed Coolant fed directly into the nipple, which is therefore particularly well cooled. It is particularly simple expediently achieved that the cooling liquid is fed centrally at the lower end of the nipple cavity and from there rises through the annular space between the outer circumference of the protruding flow pipe and the cavity wall of the nipple, the comparatively small distance between these boundary walls of the nipple channel to a comparatively lead high flow rate, despite the temperatures occurring in the connection area between the both electrode sections the risk of liquid evaporation exclude. It can be seen that the nipple is also cooled evenly to a particularly high degree, so that high thermal loads and deformations of the nipple are excluded, so that the nipple lasts for a long time Times is reusable and can be easily connected to or detached from the electrode sections.

In an advantageous embodiment, the flow pipe ends at an axial distance from the closed lower end of the Nipple, the open upper end of which surrounds the protruding flow pipe with a radial distance. There are then no special Outlet openings at the lower end of the flow pipe, wherein the cooling liquid is advantageously directed to the thermally most stressed lower end of the nipple will. Any additional measures to guide

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the coolant inside the nipple can be omitted.

An exemplary embodiment of the invention is explained in more detail below with reference to a schematic drawing, with the aid of FIG Understanding first the improved according to the invention known training is treated.

Fig. 1 shows the assembled electrode in a perspective view;

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

FIG. 3 shows the embodiment according to the invention in a partial section corresponding to the representation in FIG. 4;

Fig. 4 shows in perspective the nipple detached from the upper electrode portion together with a tool used to connect and disconnect.

909847/6708

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According to FIG. 1, the composite electrode 10 comprises an upper metallic section 12 and a lower one Consumption section 14. At junction 15 is means are provided for firmly connecting the two sections to one another. This connecting device will be described later. An electrode clamp 16 of known type is provided which includes a support arm 18 which extends from a known type of control device, not shown, to the electrode terminal 16. As usual, the electrical current is passed along the arm 18 and through the clamp 16 to the compound Electrode 10 applied. The known control device, not shown, regulates the vertical height of the assembled Electrode 10 to the most favorable arc conditions in accordance with the practice already practiced to achieve.

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

The composite electrode 10 shown in FIG. 1 is inserted downwards through an opening in the roof or in the upper wall of an electric arc furnace of the standard design, wherein the roof opening is sealed in a known manner against the escape of gases. These parts are known and therefore not shown.

The upper or metallic portion 12 of the composite electrode shown in detail in FIG. 2 10 can be made of iron or an iron alloy

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be. It has a cylindrical outer wall 22 and one cylindrical inner wall 24, which is arranged concentrically and offset inwardly from the outer wall 22 at a distance is, whereby a channel 26 of annular cross-section is formed between the two walls. The channel 26 is as an upward branch of a cooling water circulation within the metallic section 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 dimensioned is that it extends over the outer surface of the outer wall 22 extends out, as can be seen from both figures.

A first transversely extending partition wall 30 is spaced located below the top wall 28 and extends only within the inner wall 24 to which it is welded is. Above the partition wall 30, the inner wall 24 is provided with several openings 31 so that the through the annular channel 26 upwardly flowing cooling water easily and without great flow resistance can reach an opening 33 which is in communication with an outlet port 34 extending from the upper end of the Outer wall 22 extends radially outward.

Another partition 36 is near the lower end of the Section 12 provided. This partition 36 also extends only within the boundaries of the inner one Wall 24 to which it is welded.

A central axial tube 37 extends downward through the top wall 28 and the partition wall 30 and ends at a central opening 38 in the partition wall 36, so that Water can flow down through the pipe 37 into the area below the partition 36.

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At the lower end of the outer wall 22, a component 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. About the upper Extending open end of the inner frustoconical wall 36 is a circular plate 48. That of the annular Channel 42, the plate 48 and the partition wall 36 bounded chamber forms a substantially circular Channel with a downwardly protruding circumferential section, which serves to cool liquid from the lower end of the tube 37 radially outward to the lower end of the annular Channel 26 to lead. As can be seen from Fig. 2, the inner wall 24 extends down into the ring- ' shaped channel 42, whereby the cooling water is forced continuously along the inner surface of the component 40 to flow, whereby a uniform cooling of the component 40 is guaranteed. Would be the inner wall 24 do not extend down into the channel 42, there would be a risk that the water at the lower end of the channel does not participate in the recirculation flow, becomes overheated and evaporates, which could lead to explosions.

In the lower end of the annular channel 26 are several arranged in the longitudinal direction extending guide vanes 47, which reduce the turbulence as much as possible and a to promote laminar flow of the cooling liquid through the channel.

The upper end of the outer wall 22 is welded to an annular flange 50 which has the same outer diameter like the top wall 28 has. The annular flange 50 and the upper wall 28 are clamped together by screw bolts 52, with a gasket disposed between the annular flange 50 and the top wall 28, around the top end of the annular channel 26 to be sealed. As can be seen

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there is no permanent supporting connection between the inner wall 26 (with the partition walls 30,36 and the central tube 37) and the outer wall 22 (with the lower Component 40). It is advantageous to carry out maintenance work, inspections and the like. The entire to be able to remove the inner part from the outer part of the upper section 12. For this reason the annular flange 50 was provided, the only one Junction between the two parts at the top End by means of the screw bolts 52 is present.

A T-shaped coupling 54 is screwed onto the upper end of the central tube 37, and a water inlet port 56 is connected to the coupling piece 54. In the other opening of the T-shaped coupling piece 54 a safety head 57 of known type is screwed in.

At the lower end of section 12, the inner surface of frustoconical wall 46 is threaded, which can be screwed to the threads of a graphite nipple 59, which is of the type as they already used to connect two graphite cylinders together is used. The consumable graphite electrode also has a threaded receptacle recess 60 at its upper end in order to receive the other end of the screw nipple 59 penetrating on both sides. -.

It can be seen in particular from FIG. 2 that the diameter of the graphite section 14 which is consumed is the composite Electrode 10 has a smaller diameter than the upper section 12. So far the electrodes are Usually somewhat oversized for reasons of mechanical strength, so it is the diameter the electrodes are somewhat larger than the electrical requirements make necessary. In the embodiment according to the invention, however, the diameter of the graphite section

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51 908

of the composite electrode can be reduced to the minimum value for considerations other than mechanical Strength is required because the upper end of the graphite portion 14 because of the contact with the water-cooled metallic portion 12 is cooled, thereby reducing the extent to which the graphite material oxidized away on its surface. Accordingly, the initial strength of the connection will be maintained between the two sections. Furthermore, it is not required to be high. Requirements for ■ the surface properties of the graphite section 14

must be observed in order to establish a good electrical connection.

In the subject matter of the invention, the terminal 16 is arranged directly on the upper metallic section 12, so that a metal-to-metal contact is present with excellent electrical conductivity.

Because the greater part of the interior of the upper section 12 is kept free of water, the weight can of the entire electrode can be reduced to a minimum. In the construction shown in Fig. 2 can the total weight of the upper section to a diameter equal to the weight of a conventional graphite electrode lower value. This reduces the weight of the electrode pole that the arm holds 18 is assigned, must lift, and this reduces the cost of maintenance, while at the same time the lifting speed increases.

The junction where the consumable section and the non-consumable section of the composite Electrode are connected to one another, can be arranged overall at a lower point of the electrode than is the case with the lowest connection in the

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known electrodes is the case. Hence, creating random junk holes or furnace movements leading to a sideways lead to the force acting on the electrode, due to the smaller moment arm, a lower bending load in the connection area, whereby the risk of breakage is reduced. Furthermore, every break at the junction means one smaller loss of electrode weight because the connection point is located lower or closer to the electrode tip is.

It is useful to have the water-cooled section with a absorbent form so that each occurring Instead of thermal expansion of the lower section and the graphite connecting pin into a tighter connection leads to a relaxation.

Together with the single metallic upper section 12 of the electrode, lower electrode sections of different diameters can be used. So far, the electrode diameter was fixed to a single size, because of the high cost of replacing the electrode terminals.

If desired, the lower electrode section can be provided with a coating that is resistant to oxidation will. The coating can be applied to the entire surface must be attached because the lower electrode section is not encompassed by the clamp for transmitting the current. The coating can even be done during the manufacture of the graphite portion of the electrodes. Alternatively a jacket can be used to reduce oxidation losses. With the previous electrode design The different properties of the graphite and the coating material cause a non-uniform one Expansion and advancement of the sheath. Likewise, the sheathing is attached to the electrode by means of Rivets or screws because of the fragility of the graphite

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difficult. In the embodiment according to the invention, however, the sheathing material can be used on the non-consumable upper section can be suspended by means of a support device. The support device can be designed in such a way that that the electrode sections can be easily replaced.

The remaining volume within the upper metallic portion 12 of the composite electrode 10 is complete 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 warming, one is Connecting line 67 is provided which extends through the partition wall 30 and through the top wall 28.

The training according to FIGS. 3 and 4 largely corresponds to the training described above. The relevant parts are therefore provided with the same reference numerals to which a distinction is added. Deviations are only at the lower end of the metallic upper electrode section 12 'and at the double-conical screw nipple 59 'provided. Thus, the circular plate 48 is absent at the lower end of the electrode section 12 '. Instead goes the upwardly tapering incision surrounded by the screw-threaded frustoconical wall 46 ' is, directly by means of a bottom opening into the interior of the electrode section 12 »over. However prevented the partition wall 36 'connects to the air space within of the inner jacket 24 '.

The main difference compared to the embodiment according to FIG. 1 relates to 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.

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The screw nipple 59 has a central cavity 65 and is designed with an open upper end 66, while the lower end 67 is closed.

The central axial tube ^37f extends further downwards than the tube 37 according to FIG. 2. As can be seen from FIG. 3, the tube 37 'extends axially downwards 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 flows radially outwards and downwards to the lower end of the annular channel or return channel between the outer jacket 22 'and the inner jacket 24' of the upper electrode section 12 '.

The screw nipple 59 ^! has at its lower end 67 two diametrically opposite bores 70, which can receive projecting pins 72 of a hand-operated tool 74, which is used for sealing screwing or tightening of the screw nipple 59 into the incision at the lower end of the electrode section surrounded by the frustoconical wall 46 12 'serves.

Tests have shown that the cooling in the ■ connection area especially between the consumable lower section and the metallic upper section good is. and thereby a tapering of the lower graphite section limited to an area further from its upper end. Furthermore, the connection point remains substantially cold between the two electrode sections, and accordingly the sections can be easily removed from the nipple, so that a used graphite section can be replaced.

609847 / Θ706

Claims (2)

------ · ■ DP ..- ING. FRANZ VUESTHOPP PATENT LAWYERS ':: ...' :: -. . UR.VHIL. PREDA TUESTHOFl '(1027-ϊ-, ό) WUESTHOFF-v.PECHMANN-BEHEENS-GOETZ - ». ^ ■ '^ DIPL.-CHEM.DR. E. BARON OF PECHMAKN PROFESSIONAL REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE DR.-ING. DIETER BEHRENS MANDATAiREs agrees pres l'ofpice europeen des brevets dipl.-ing .; dipl .- \ tirtsch.-ing. rupert goetz D-8000 MUNICH 90 2918757 SCHWEIGERSTRASSE 2 tjblefon: (089) 66 20 ji telegrammiprotectpatent telex: j 24 070 1A-51 908 Patent claims: Λ,) Electrode for electric arc furnaces, consisting of an upper section made of metal and a replaceable lower section made of consumable material, which have a substantially cylindrical shape and are connected to one another by a screw nipple or the like, the upper section having one at the upper end encloses an open cavity and has a liquid cooling device with a flow channel and a return channel, which start from the upper end of the section, extend essentially over the entire length of the section and at the lower end of the section in particular through a radial channel that essentially completely fills the electrode cross-section with connect tied together the flow guide vanes with each other / are, wherein the flow channel is formed by a central tube extending through the upper section, the return channel is an 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, according to patent ... ... (P 27 39 483.8), characterized in that the upper electrode section (12 ¹ ) has a bottom opening communicating with the return channel at its lower end, that the nipple ( 59 ') is metallic and hollow and has an open upper end (66) through which the nipple cavity (65) communicates with the return channel, and that 809847/8708 ■ - 2 - 51 908 the central ^{flow pipe (37 1} ) protrudes with its lower end into the nipple cavity (65). 2. Electrode according to claim 1, characterized in that the flow pipe (37 ¹ ) ends at an axial distance from the closed lower end (67) of the nipple (59 '), the open upper end (66) of which with the protruding flow pipe (37 ¹ ) Radial distance encloses. §09847 / 0708