DE6605816U - ELECTRODE IN CONTACT WITH A MELT - Google Patents

Description

RA..287 71 k ^ U

Aktiengesellschaft Brown, Boveri & Cie _{o >} Baden / AG

Electrode in contact with a melt,

The present invention relates to a melt-in contact electrode for a furnace, in particular one Bottom electrode arranged in the lining of an electric arc furnace.

In more recent times, the importance of a direct current arc has increased in metallurgical arc furnace systems to use an electrode arranged in the furnace and in contact with the melt »

5.4.66 / hg 6605816-9.7.70

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A direct current arc, however, has an alternating current arc compared to a V ' several advantages, namely:

greater stability and regularity of the arc,

- Less, in itself undesirable, supply of graphite into the melt when using a graphite electrode as the anode and the melt as cathode,

less heating of the graphite electrodes,

- less graphite consumption for the electrodes =

It is now capable of generating a direct current arc without Use of a rectifier or converter groups It has been proposed, starting from a Viechseis voltage, to erasel the rectification by the arc itself, inden the properties that r.ich from the physical or chemical inequality of the electrodes used. Dar.it has the training of the .Itromüberganges from the melt to a Speisev.-eehselstroraquelle leading ladder, especially their neutral ladder, once again gained in importance »

It is known, when such bottom electrodes, electrode bodies made of graphite or of a metal, in particular iron

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the furnace is used for smelting iron or steel.

Carbon electrodes do not meet the thermal requirements fully, ν / ei π en the! tech part on that the The melt is carburized by the contact with the electrodes will. It is generally used in steel production completely undesirable as this should be as low in carbon as possible.

Metal electrodes, especially iron electrodes, have the disadvantage that they have a melting point that is too low, so that they are largely molten during operation, or that they alloy with the melt, even if they have a sufficiently high melting point, and so on change their composition. It is therefore essential to cool metal electrodes. A previously used water cooling of the electrode body by means of coolant channels arranged inside the body has the disadvantage that on the one hand the electrode melts if the coolant fails and on the other hand coolant channels can be exposed if the electrode body is inevitable so that the coolant enters the melt and creates the risk of explosion _o

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Zv; eck cor invention is an electrode to be sharp, soft does not have the disadvantages mentioned. According to the invention the electrode is characterized in that the electrode body has two electrically and thermally connected, one behind the other arranged Tsile, wherein the melt facing first part of the electrode body made of one of the metal Melt at least similar metal and the second, facing away from the melt, the transfer and radiation of the The heat-serving part consists of a good conductor of electricity and heat.

The invention is illustrated below with reference to figures, for example explained. Show it:

FiK. 1 i * a section of a first export, for example one in the lining of an electric arc furnace Podcne electrode,

Fig. 2 shows a section through the "nt" ktbolzen air.ir further Bottom electrode,

Fig. 3 is a side view of a carrier for aen bolt of Fig. 2, with busbars,

Fig. 4 shows a section through the conductor rails along the line IV-IV of Figure 3 _o,

Fi. ^ C5 a? Dr i.uf calibrates to completely di- ^ jidige bottom electrode ~ err ^"; rs Figures 2 to _4}.

6 shows a section through part of an electric arc furnace with an electrode according to FIGS. 2 to 5.

According to FIG. 1, a peg-shaped electrode 3 is arranged in the lining or ramming 1 of the bottom part of an electric arc furnace, which is held on its outside by the furnace chamber 2. The electrode 3 consists of two parts 4 and B, from v. ^r calibrate the one part 4 with its end face approximately in the same plane as the inside of the brickwork 1 and the other ':' part 5 dries out over the furnace boiler 2 out into the outer room. The two parts 4 and 5 consist of different Ket .'- llen; they meet in the transition zone G »

Of the melt in "jerührunp properties and to provide ^ ^ of the lining 1 e part 4 of the electrode 3 is composed of eir.em -?.? Et ll, UEPs at least similar to that of the melt is at least eggs etters no undesirable constituents in the melt er.tht.lt. If the furnace is used to melt iron or steel, then part 4 of the electrode is also made of iron or steel, which extends into the outside space

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As a result of the conicity of the embedded in the brick lining 1
It is possible for the electrode 3 to be attached to the furnace kettle 2 in a simple and advantageous manner. The cooling surface 7
has, for example, three bores 9 or slots,
one of which can be seen in the figure. Through this
Bores are guided from below threaded bolts 10, the
are screwed into nuts 31 welded to the furnace tank.
Between the cooling surface 7 and the head of each threaded bolt
10, a compression spring 12 is arranged. As a result, the cooling surface 7 and with it the electrode 3 are moved upwards, ie into the

extending part 5 of the electrode 3 consists of a]

Heat and metal that conducts electricity well, preferably j made of copper ο Part 5 is used to radiate heat _o Er]

ι can be provided with additional cooling surfaces. I.

In the figure, a plate-shaped cooling surface 7 is shown, many radiating heat and transferring it to the ambient air by natural convection. In order to avoid any heat j congestion due to cross-sectional constrictions in the direction of the
increasing temperature in the electrode body

the peg-shaped electrode 3 is conical. From the \

g the same reason and to increase the radiating surface

CI CJ-ll? V CJ. l / lCXUnc <-> CXULJ. ·;

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conical lining pressed in "In order to prevent the spring 12 from heating up and thus becoming lame, it is supported on the cooling surface 7 on a ceramic disk 13" In addition, a ceramic tube can also be attached between the spring 11 and the threaded bolt 10. The resilient attachment of the electrode 3 to the furnace shell 2 enables the automatic compensation of axial heat movements of the electrode 3, which occur when the electrode is heated by the melt and when the melt is cooled after the melt has been poured out «

If the electrode 3 and the furnace vessel 2 can be earthed together, no insulation is necessary between these two parts , as shown ± xi in the figure. Otherwise, the section in the furnace chamber 2 must be larger for the electrode, so that the electrode 3 and the furnace chamber 2 cannot touch. In addition, it is advantageous to insert ceramic sleeves into the bores 9 of the cooling surface 7. The power connection is made, zvreckiaässigerweise by connecting one or more busbars (not shown) -with; the cooling surface 7.

The transfer path of the one in contact with the melt Part 4 of the electrode, made e.g. of iron or steel

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with the other part 5 made of copper for heat radiation have little or no additional heat and electrical resistance. It is therefore advantageous to manufacture the electrode 3 in one cast by using the Iron existing part 4 on the previous casting of the Part 5 still liquid copper is poured on, the two metals mixing in the transition zone 6. The reverse sequence for pouring is also possible.

It is advisable to use a scaling of the copper To prevent part of the electrode and the cooling surface 7 by pretreating the copper surfaces accordingly for example by diffused aluminum, Schoopizing, galvanic treatments, etc.

The two-part electrode described above achieves that on the one hand the melt through the electrode metal does not is contaminated and, on the other hand, the part of the electrode which is in contact with the melt Thermal energy is quickly passed on and distributed without the need for forced cooling in the furnace or in the brickwork. The electrode is designed so that the transition 6 from part 4 (iron) to part 5 (copper) with Security no longer melts.

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This is achieved in that the cross section of the with Melt contacting part 4 of the electrode is dimensioned so that the current present through this part ohmic losses do not or, compared with the heat generated by the melt, only heats up very little additionally. The radiating surface of the second part 5 of the electrode must be larger than that of the part 4. Since copper is one has a very low thermal resistance, the temperature drop in part 5 is very small. The comparatively large thermal resistance the part 4 made of iron or steel, on the other hand, results in a very large temperature drop. To this In this way, the temperature in the transition zone 6 from iron to copper can be kept low.

It can be shown that an electrode made entirely of steel at a melt temperature of 1800 C, assuming that the lining 2 of the furnace is worn down to a level 14, in a further to the outside, in the figure at 15 point would be about 1460 C, so it would be liquid. The existing also made of steel electrode Kuhlfläche 8 would in this case have a temperature of about 540 ⁰ C.

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If, however, the electrode is made in two parts according to the invention, then, under otherwise identical conditions, a temperature of only 1200 G prevails at the point 15 mentioned, at which the electrode in the point mentioned is certainly still solid a temperature of around 670 ⁰ G, so it is safely in the solid state. The electrode cooling surface 8 radiates here with a ^r e "Tnemtur of about 650 C ₉

DiPS ^ r comparison shows that a steel electrode without forced cooling; may be selected from ^ ichörheitsgründen not be considered because it is too deep into the lining into .flüssig and a breakthrough to the outside quite possible _o Forced cooling with a liquid medium but had to extend into the interior of the electrode and as close as possible with the The electrode surface in contact with the melt extends, which would open the cooling channels to the side of the melt with increasing wear of the lining. These disadvantages are completely avoided with the electrode described

The amount of heat in the one in contact with the melt Electrode part 4 can be significantly increased by the fact that outside the furnace duct (and not inside the brickwork) forced cooling by a gaseous or

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Medium is provided. For example, the cooling surface 6 and / or the busbars connected to it can be puffed with cooling air. Moved by this? ' the solidification point of the slectrode part 4 in contact with the melt moves even closer to the melt.

The electrode described also allows the wear and tear of the brickwork to be monitored in a simple manner, specifically by measuring the temperature accordingly. It wird- this, conveniently the temperature of the cooling surface 7 measured at the location of the recess 8, for example with an optical pyrometer, a thermocouple, or the like. Is according to the above ZahlenbeisOiel in Neuzust ^ nd the electrode, the Tenrx r & ture c <& r FIi ⁵ before 8 about BlO ⁰ C,? O it rises insane. The worn condition of the electrode and the lining (wear up to level 14) must be about Btio "C. These temperature differences can easily be determined.

Another conceptual form of the Mektrooe is shown in Fig. 2 to 6, it consists in the fact that the thief facing part is placed on the other part.

A bolt 21 of the electrode shown in FIG. 2 has a cylindrical part 22 on which a

23 follows · The

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Part 23 is also frustoconical with a recess 24 provided «, the end face 26 of the cylindrical part 22 is in contact with the melting material to be heated o The frustoconical recess 24 serves as Contact surface *; with a carrier 30 shown in Fig. 3, the upper part 31 of which is designed as a corresponding truncated cone is, so it includes the same angle «. A cylindrical part 31 adjoins the frustoconical part Part 32, which is provided with several vertical slats 33. These lamellas 33 are milled in, for example of slots in the lowermost part of the carrier 30, which is designed as a rectangular block

The slots located between the slats 33 are used to accommodate strip or rod-shaped busbars 34, of which several for the purpose of establishing the current connection between the melting material and the one that feeds the arc Alternating current sources are arranged in parallel side by side. The busbars 34 are fixedly connected to the lamellae 33, for example by a plurality of screw bolts 35 or also by Clamps with the lamellas pressed together <.

_{The bolt 21 consists of a similar metal as that of the melting material o} If the electric arc furnace is intended for melting iron or steel as usual, the bolt 21 is advantageously made of soft iron o The trafer 30 and the busbars 34 are to achieve a large electrical and thermal conductivity made of copper.

The bolt 21 of the electrode is placed with its frustoconical inner surface 24 on the corresponding frustoconical support part 31 _o This allows the different thermal expansions of the soft iron of the bolt 21 and the copper of the support 30 to be absorbed without mechanical stresses occurring. In order to avoid oxidation of the inner surface 24, this inner surface 24 is provided with a copper layer 25 which is applied, for example, by electrolytic means. The copper layer achieves a low electrical transition resistance, good conductivity and prevents welding of point-like contact points:

In Fig. 6, the installation of a contact piece, which is designed according to Figures 2 to 5, is shown. The the Bolt 21 and the carrier 30 having electrode is in

used the bottom of an electric arc furnace. The bottom and the walls of the arc furnace shown in detail consist of an outer sheet metal niantel 40 and an inner refractory lining 41. The electrode is inserted so that the end face of the bolt 21 is at least approximately in one plane with the inner surface of the lining 41. The carrier 30 is connected to the power supply 34 consisting of several rails, which is arranged along the outer furnace wall and leads, for example, to the Kulleiterklemrae of a three-phase supply transformer, whose star-connected secondary windings are connected to one electrode each a channel 44 through which cooling air is blown in the direction of arrow 45 _o

The carrier 30 for the bolt 21 is attached to the sheet metal frame 40 of the furnace wall in a manner not shown. The bolt is simply placed on the carrier and causes the stroking and heat transfer through its own weight. Since the carrier 30 is expediently made of soft copper, are any irregularities in the mutual contact surfaces of the bolt 21 and the carrier 30 easily balanced by the pressure of the bolt 21

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in the heat movement cos bolt 21 pushed for buses
ηηά nods on the surface between the bolts 21
and can penetrate the carrier 30 "

2m the operating state of the arc furnace is heated, the
Electrode, on the one hand due to the Sfcrösdureh
by the electrode and on the other hand due to the τοπ the
Melt, with. which the Slelrtröde in touch; steiit. ₃

To install the electrode in the furnace wall 40 is in the sheet metal jacket
an opening is provided for the carrier 30, to which _s

cover a fender 42 is arranged. This lies:

on the sheet metal shell 40 via an asbestos intermediate layer 43. I.

■ s

After the bolt 21 has been placed on the support 30, the refractory lining 41 is wrapped around the bolt 1

I brought order to prevent powder or dust-like ί components of the liner 41 during the time between f the bolt 21 and the carrier 30 fall, which due to the myiö J bsi u ^ r Erviärnunfi alternating cooling of the electrode |

resulting movement of the bolt 21 relative to the carrier 30 | rary readily possible, a cover tube is superiors 46 f see what the Auskleidun saaterisl ^ \ ^r o "i carrier 30 and. |

I keep away from the lower part of the bolt 21. In addition, the I

lower end face 35 of the bolt 21 at ^ eschräf ^ t (Fig _o 2 1

and 6), '»r through the penetration of Frenidstof f e j

_o The heat supplied standing with the melt in contact with end face 26 of the bolt 21 of the electrode <{: FIG _e 2) is thus also in the molten state. In order to avoid contamination of the melt by the metal of the electrode, the bolt 21 of the electrode, as already mentioned, consists of a metal _{or the like that is similar to the metal of the melt}

The heating of the Electrode is proportional to the cross section of the contact piece, so in particular proportional to the cross section of the cylindrical part 22 of the bolt 21, while the heating caused by the passage of current this cross-section is inversely proportional. Taking into account the length of the electrode, which depends on the thickness of the furnace wall can this be done in a way that is known per se

dimension so that the heating is minimal.

As a result of the large formation of the lower part of the bolt 21 as a truncated sail, the frustoconical bearing surface 24 of the bolt 21 on the carrier 30 and the formation of the power supply as several from each other through an air gap; separate rails 34, heat is transported by conduction and convection from the deeply frozen point of the bolt 21, namely the end face 26, to the cooling air beirärr & trvö -jg _{Q Ί}

It is thereby achieved that in the cylindrical part of the bolt 21, the end face 26, which is in the melted state, is adjoined by a zone 27, indicated in FIG. 2, in which the metal of the bolt 21 is in a soft, dough-like state. Below this zone the metal is solid and its temperature decreases every hour towards the connection of the busbars 34, so that it is possible at the current and Y / heat flow transition point from the bolt to the carrier 30, i.e. at the support surface 24 with the truncated cone-shaped part 31, achieve a temperature su that is no more than 700 ° C. This is achieved by appropriate selection of the diameter and length of the cylindrical part 22 of the bolt 21, the strength of the current ₃ flowing through the electrode, the thickness of the furnace lining and the amount of heat to be dissipated by conduction being decisive.

At the time the S. melt is poured out of the furnace, in which the electrode is at its highest temperature and in the mentioned condition can run the cooling of the Electrode can be strengthened for a short time. This additional cooling has the effect that the end face 26 of the Bolt 21 of the electrode solidifies and assumes a soft, dough-like state. When the furnace is tilted accordingly

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No material was carried away by the melt from the bolt 21 of the electrode, so that due to the brief temperature decrease the previously melted metal of the electrode is automatically replaced.

The additional cooling of the electrode can be achieved, for example, that the normally through Natural convection of the busbars 34 cooled by the circulating air are exposed to a forced flow of cooling air.

If the busbars normally already, as shown in Fig., In a cooling air generated by a fan flow are arranged, this cooling air flow can be reinforced or an additional cooling of the Busbars with a liquid or gaseous medium, such as water or steam, which can also circulate in corresponding channels provided in the trafer 30, in operation be set.

Because of the good conductivity between the end face of the bolt 21 and the busbars 34, the additional cooling takes effect on the end face 26 without any major delay. It is sufficient in this case, the temperature decrease at the end face 26 to about 200 ⁰ C.

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- IS -

The electrode described has the further advantage that it can be replaced without a complete renewal of the furnace lining at the bottom of the furnace would be necessary «. After the insertion of a new bolt 21, only the one in the immediate vicinity of the bolt has to be The furnace lining must be reinstalled.

The use of the electrodes described is not restricted to electric arc furnaces; rather, a corresponding Electrode can also be used in other facilities with high temperatures »

Claims (19)

9/66 RA.287 714-2.6.66 Patent claims: 1) Kit of a melt in contact steheucle electrode arranged for a furnace, in particular in the brick lining of an arc-οΓens bottom electrode, characterized in that the electrode body has two power and heat conductively connected, successively arranged parts (4, 5 resp _o 21, 30} has, v / o in which the melt facing the first part (4 or 21) of the electrode body made of a metal at least similar to the melt: lethal1 and the second part facing away from the melt and serving for the transfer and radiation of heat {5 and 30, respectively ) consists of a good 3tron_ and heat conductor. 2) Electrode according to claim 1, characterized in that the second part (5 or 30) of the electrode body made of copper consists. 3) Electrode according to claim 1, characterized in that the electrode body has the shape of a pin, one end face of which is in contact with the melt and the other end of which extends beyond the outer wall (2 or 40) . 9/66 4) electrode according to claim 3, characterized in that the pin widens at least partially conically in the direction from the melt to the outside of the furnace wall (2). 5) Electrode according to claim I _3, characterized in that the two parts (4, 5) are continuously connected in a transition zone (5), for example by pouring the metal of one part (4) onto the still molten metal of the other part (5) _o 6) Electrode according to claim 1, characterized in that the second part (5 or 30} of the slectrode body (3) with additional cooling surfaces (7) located outside the furnace wall (2) are provided. 7) Electrode according to claim 6, characterized in that the cooling surface (7) is plate-shaped and together with the second part (5) of the electrode body in one piece. 8) Electrode according to claim 1, characterized in that the electrode body is resiliently attached to the furnace wall (2) in order to prevent axial thermal movements of the electrode body compensating S / 6 6 9) Electrode according to claims 7 and S, characterized in that ds: c- the cooling surface (7) .nit several openings. (9) 52, U = -ohruugen or Schlitaen, versesven igt _> through bolts (10) attached to the Cfenv'-nd (2) and then between the head of each bolt (10) and the cooling surface (7) a Compression spring (12) is arranged. 10) electrode according to claim 1, characterized by a with the bolts (21) and a carrier (30) connected to a power supply (34-), 3 on which α d-3r Βτίζεη (21) is placed, 11) "Slektrole according to claim 10, characterized in that the bolt (aufval.Tt 21) el'ien cylindrical portion (22) having a with the -S crLTi el ζ well in non-stationary face (26) .i: i /, ^r elchß: i is followed by a conical-lstunpffÖrniig widening part (23) which is also provided with a truncated cone-shaped , rtirnsοii-ig open recess (24}. 12) Electrode according to claims 10 and 11, characterized in that the carrier (30) is at least partially designed as a truncated cone (31) which includes the same angle as the frustoconical recess (24) of the bolt (21) ο 9/66 13) Electrode according to claim 12, characterized in that the carrier (30) is provided on its lower part with several vertical slats (33). 14) Electrode according to claims 10 and 13, characterized in that that the power supply has several busbars (34), the ends of which between the slats (33) of the carrier (30) are arranged. 15) Electrode according to claim 11, characterized in that the frustoconical recess (24) made of iron Bolt (21) is provided with a copper or silver layer (25). 16) The electrode according to claims 1, 6, 10 and 14, characterized in that the cooling of the electrode extending or by cooling outside of the furnace wall (2 .. 40) electrode parts (7 located, _r is carried out 33, 34), for example by natural Air cooling or by forced cooling. 17) Electrode according to claim 16, characterized in that means for increasing the cooling, e.g. a fan or a cooling circuit with a liquid or gaseous medium are provided. 9/66 - 24 - 18) electrode according to claims 2, 8 and 10, characterized in that that the parts (5, 7, 30) made of copper are provided with a non-scaling surface, e.g. through Sindif foundation, of aluminum, galvanic treatment or the like. 19) Electrode according to claim 1, characterized in that for monitoring the wear of the first part (4 or 21) of the electrode body and / or the brick lining (2 or 4l) means for detecting the temperature on a furnace wall (2 or 4o) located point of the second part (5 or, J> 0) of the electrode body are provided. Public company BROWN, BOVEHI & CIE. 66ö5816-9.?.? Ö