CA1198760A - Electrode holder for arc furnaces - Google Patents
Electrode holder for arc furnacesInfo
- Publication number
- CA1198760A CA1198760A CA000415103A CA415103A CA1198760A CA 1198760 A CA1198760 A CA 1198760A CA 000415103 A CA000415103 A CA 000415103A CA 415103 A CA415103 A CA 415103A CA 1198760 A CA1198760 A CA 1198760A
- Authority
- CA
- Canada
- Prior art keywords
- electrode holder
- sectors
- holder according
- metal shaft
- ring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B7/00—Heating by electric discharge
- H05B7/02—Details
- H05B7/10—Mountings, supports, terminals or arrangements for feeding or guiding electrodes
- H05B7/101—Mountings, supports or terminals at head of electrode, i.e. at the end remote from the arc
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B7/00—Heating by electric discharge
- H05B7/02—Details
- H05B7/12—Arrangements for cooling, sealing or protecting electrodes
Abstract
Electrode Holder for Electric Arc Furnaces ABSTRACT
An electrode holder for electrodes used in electric arc furnaces, comprising a cooled metal shaft that is surrounded by a protective jacket which is basically a hollow cylinder consisting of high-temperature resistant moldings. The protective jacket surrounds and protects either that part of the electrode holder which is located within the furnace or the part in the clamping jaw zone.
In order to create a protective jacket for the cooled metal shaft of electrode holders of the present type which fully meets all thermal, mechanical, and electrical requirements of electric arc operations, which has a simple design, which is easy to mount and to repair, which guarantees a good heat transfer to the cooled metal shaft, and in order to improve the service life of the protective jacket as such, the protective jacket consists of individual moldings which may be put together to rings, or of ring-shaped moldings which are connected among each other and/or to the metal shaft in a form locking and/or resilient manner.
An electrode holder for electrodes used in electric arc furnaces, comprising a cooled metal shaft that is surrounded by a protective jacket which is basically a hollow cylinder consisting of high-temperature resistant moldings. The protective jacket surrounds and protects either that part of the electrode holder which is located within the furnace or the part in the clamping jaw zone.
In order to create a protective jacket for the cooled metal shaft of electrode holders of the present type which fully meets all thermal, mechanical, and electrical requirements of electric arc operations, which has a simple design, which is easy to mount and to repair, which guarantees a good heat transfer to the cooled metal shaft, and in order to improve the service life of the protective jacket as such, the protective jacket consists of individual moldings which may be put together to rings, or of ring-shaped moldings which are connected among each other and/or to the metal shaft in a form locking and/or resilient manner.
Description
7~3 Electrode Holder for Electric Arc Furnaces FIELD OF THE INVENTION
The invention relates to electrode holders for electric arc furnaces comprising a water-cooled metal shaft and a working part of consumable material, with the metal sha~t being, at least partly, surrounded by moldings of high-temperature resis-tant material.
BACKGROUND OF THE INVENTION
Electrodes with electrode holders of the type mentioned are available in two basic designs. According to the first design the electrode consists of two axially aligned sections, i.e.
the electrode holder, which constitutes the upper section, comprising a cooled metal shaft, a,nd, at its lower tip, the active part of consumable material where the electric arc is produced. This type of electxode is generally known as combination electrode. With the second type of design, the active part of consumable material is axially movable within the electrode holder which basically comprises a cooled metal shaft. The active part of consumable material consumed at its lower tip may, therefore, be compensated for by axial movement. This type of electrode is generally known as conventional feed through electrode. A common criterion of both designs is that the electrode holder, i.e. the li~uid-cooled metal shaft, during operation projects, at least partly, into the interior of the furnace.
However~ electrodes for electric arc furnaces are exposed to high thermal and mechanical stress. Thermal stress conditions result from the hiqh working temperatures reached particularly in the production of electric steel. Mechanical 7~
stress ls caused e.g. when the el~ctrode, upon its insertion inko the furnace, hit~ scrap material, or it may also result from movements of ~he moL~en metal or scrap material, or from vibrations caused by the electric arc.
In order to ensure th~ usefulness of these electrode~ it is, therefore, imperative to effectively protect the cooled metal shaft of the electrode holder, which during operation is in the interior of the furnace, against th~ thermal and mechanical stress me~tioned. Numerous solutions have been offered to this proble~.
The electrode holder of the combinakion electrodes described in BE-PS 867 876 takes the for~ of a metal shaft which contains the cooling syst~m and which is covered with a high-temperature resistant coating on the outside. In order to improve the adhesive capacity of this coating on the sl~eath area, the metal ~haft has hooks holding the coating in place.
Similar combination electrodes are described in GB-PS 1 223 162.
Their electrode holder is completely covered with a protective, ceramic coating. With this type of solution, attention has to be paid to the thickness of the ceramic coating, which should be as small as possible, and to the extent of lts application, which should include the electrode holder proper to ensure the insulation of its pipes. These pipes serve not o~ly as cooling water ducts but also aR current supply to the active part of graphlte~
~heEuropean patent application 0 010 305 published April 30, 1980 (U.S. Patent 4,291,190 is equivalent~ describes a combin-ation electrode with an electrode holder comprising a mekal shaft ~hich is electrically insulated against the current-carrying cooling system and which can be sufficiently cooled by a high-temperature resistant material between the cooling sys-tem and the metal shaft. The lower section of the metal shaft, ~3~'7~
which constitutes the electrode holder, is covered with a ceramic coat that is also secured by hooks.
The combination electrode of DE-AS 27 25 537 has a metallic~
liquid-cooled upper section constituting the elec-trode holder, which is insulated by a high-temperature resistant material covering thermally conductive pro~ections. The purpose of these projections is to prevent a direct mechanical contact with the line system if, as a result of high local stress~ the high-temperature resistant material is locally damaged by rigid scrap material. At the same time these projections act as a kind of fusep thereby preventing excessive currents from passing.
Finally, DE-AS 27 30 884 describes a conventional feed-through electrode whose cooled metal shaft, which constitutes the electrode holder and serves as passage through which the active part of graphite is fed, is covered with high-temperature resistant ma-terial. At the same time the metal shat has projections directed radially towards the outside which fasten the high-temperature resistant material. Thlese projections, which are distributed along the periphexy and in axial direction as evenly as possible, are designed to ensure a more constant cooling and better adhesive capacity of the high-temperature resistant material. This solution corresponds to the protec-tive coat designs mentioned in connection with combination electrodes. According to the most recent state of technology, the same solutions are offered for the electrode holders of combination electrodes and conventional elec-trodes.
All these electrode holders have one disadvantage in common, i.e. that the protective jacket, even if it is only slightly locally damaged, has to be removed from the metal shaft of the electrode holder and a new protective jacket has to be applied,which causes lengthy interruptions and high costs.
A further disadvantage of conventional electrode holders is the formation of slag and mekal layers on the protective jacket of ceramic material, which leads to disorders in furnace operation.
It was, therefore, suggested to create an electrode holder whose cooled metal shaft is protected by rings of a material containing carbon, preferably graphite. Electrode holders of this type have been employed and the protective jacket mentioned has proved extremely useful. The graphite rings act as an excellent protective coat from the mechanical as well as the thermal viewpoint. One advantage of such a protective jacket is that, i it is partly damaged, the graphite ring in question may be exchanged, while complete removal of the jacket is only required if continuous protective coatings are used. A further advantage is that the formation of slag or metal layers is avoided, for due to the destruction of the graphite surface by oxidation they keep falling off the protective jacket. One disadvantage is, however, that in some cases the rings show a certain tendency towards cracking which is caused by the different thermal expansion of the protective jacket and the metal shaft constituting the electrode holder, and, consequently, by the resulting tensions within the protective ring.
Furthermore, there is one problem that all electrode holders described have in common~, namely, how the metal parts can be fastened above the furnace lid. In general, this is achieved by means of clamping devices. Considering such factors as easy handling or ~uality of electric contact it is advantageous to use the mechanical clamp also as a means of current transferO As a consequence, graphite or carbon moldings are usually used between the metallic part of the electrode and the clamping jaws of a bearer arm, for these moldings combine favourable current transfer properties with good mechanical and therma:L properties.
However, the way how these moldings are to be fastened to the electrodes poses problems, as the moldings may break due to the clamping forces required. This may, in turn, lead to the loss of the moldings when, in varying the place of clamping e.g., t~e clamps have to be re~loved.
OBJECT OF THE INVENTION
The object of the presen-t invention is to create a protective jacket for the cooled metal shaft of electrode holders of the type mentioned which fully meets all thermal, mechanical, and electrical requirements, which has a design as simple as possible, which can be easily mounted and repaired, and which guarantees a good heat transfer to the cooled metal shaft of the electrode holder in order to improve the service life of the pro-tective jacket.
With regard to the electrode holder in question, this problem is solved by the connection of moldings to the metal shaft and/or among each other in a removable manner by means of form locking and/or resilie~tconnection elements.
The solution in accordance with the invention provides a protective jacket that meets all electrical, thermal, and mechanical requirements. I~ a ~resilient connection i5 used, the prestress of the individual moldings of the protective jacket makes them rest snugly on -the metal shaft of the electroda holder, which results in a good heat transfer between protective jacket and metal shaft over the entire area. This good heat transfer is achieved without inserting any filling material between the protective jacket and the metal shaft of the electrode holder~ In addition, on account of the~ resilient connection of the sectors, the individual moldings are capable of balancing tensions caused by the different thermal expansion of the material of the protective jacket on the one hand and the material of the metal shaft of the electrode holder on the other. Thus r there is no danger of the protective jacket belng damaged by this thermal expansion. The protective jacket is, therefore, in a position to meet all thermal requirements.
The s~me holds true for mechanical stress. By connecting the sectors in accordance with the inventionl i.e.among each other or to the metal part, it is possible to balance the production tolerances of the moldings so that their inner sheath area is always snuyly pressed against the sheath area of the metal shaft of the electrode holder.
In this way, compressive and bending ~orces are transferred from the protective jacket to the metal shaft of the electrode holder without any excessive strain on the material of the protective jacket as a result of insufficient contact between protective jacket and metal shat. At the same time, the metal shaft of the electrode holder is also protected by the moldings. Finally, depending on the requir~ments, the moldings are easy to mount or dismount. For this purpose, individual moldings or groups of r~oldings may be axially moved along the metal part. It is e.g. possible to connect several moldings or sectors which then form a partial ring, or to connect several partia:L rings which then form one complete ring. This means that a protective ring may be directly mounted on the metal shaft of the electrode holder. If one or several sectors of the protective ring are damaged, the damaged sector may simply be exchanged.
If the protective iacket consists of several rings each of which is made up of sectors, the ring at the lower tip of the metal shaft of the electrode holder which :is, of course, exposed to the highest strain within the furnace and, therefore, more likely to be damaged or worn than the rings arranged further to the top, should be removed first. It should be replaced by either a new ring or a ring used in the upper section of the metal shaft that is still suitable for the lower section. In this way it is possible to replace the rings successively, to reduce assembly time, and to cut the main~enance costs for the protective jacket of the electrode holder.
Advantageous designs of the electrode holder in accordance with the invention result Erom other claims as wellD
According to one version the sectors may consist of non-graphitic or partly graphitic materials containing caxbon.
This results in economical service times of the protective rings, while the properties of the carbon material with regard to slag or metal splashes are also favourable. If the dimensions of the protective rings are correct, the desired slow oxidation of carbon will be achieved especially on the hotter exterior peripheral areas of the rings, which prevents the accumulation of slag or metal parts, a disadvantage frequently observed when ceramic coatings are used.
Since the solution in accordance with the invention offers an ex~ellent heat transfer from the protective jacket to the metal shaft of the electrode holder, it is recommended that the protective jacket be made of materials that have a low thermal conductivity. Among the materials con~; n; ng carbon, the so-called non-graphitic or partly graphitic materials are, therefore, especially suitable.
If the user can do without the advantage of self-purification of the surface of the protective ring, céramic materials may also be used.
It is useful to use ceramic materials for the sectors in the upper section of the metal shaft of the electrode holder, and materials conta-ning carbon for the sectors in the lower section. Othex solutions, such as a mixed arrangement of rings or sectors of different materials, are also possible.
It is certainly an advantage that the non-positive connection of the sectors among each other and the formation of prestress,which enables the ring consisting of sectors to snugly rest on the metal shaft of the electrode holder, are achieved by spring power.
As far as the arrangement of the springs producing the spring power is concerned, there are a number of possibilities.
Each protective ring may have on~ or several spring rings, with each sp~ing ring being formed either by one spring or by several springs connected in series.
The springs are located in sector bores or recesses which are concentric to the ring. In this way the springs are incorporated in the sectors, which is a great advantage because they are protected against excessive thermal and mechanical stress.
In order to further reduce the ~herm~l strain on the springs, the bores or recesses are located near the inner sheath area of the sectors, which means that the springs and the cooling system of the metal shalt are as near as possible to each other so that the temperature in the spring zone is kept as low as possible.
The springs used may be spiral springs or leaf springs.
It is of special importance that the springs consist of a non-magnetic material in order to avoid the heating r~
of the springs as a result of hysteresis losses.
Basically r the springs should be characterized by a high heat resistance. For this reason the springs may be made of austenitic chrome-nickel-molybdenum steels or of material containing berylliumO
In accordance with another preferred embodiment of the invention, the abutting surfaces of neighbouring sectors, which lie in peripheral and/or axial direction, have at least one complementary radial graduation. Even i the abutting surfaces of neighbouring sectors do not snugly fit due to tolerances, these interlocking graduations guarantee that the sectors are well sealed, which, in turn, results in a safe protection of the cooled metal shaft of the electrode holder.
According to another embodiment the width of the sectors measured in peripheral direction is relatively small,with the abutting surfaces and the radial beam of the hollow cylinder forming an angle. This means that in relation to the respective radii the relatively thin sectors of a ring rest in an oblique manner on the metal shaft. Thus tolerances are balanced as a result of the so-called l'effect of self-adjustment", with the sectors adjusting thems~lves in a more vertical or a more horizontal position depending on the diameter of the metal shaft and/or the inside diameter of the sector ring.
This "e~fect of self-adj~stment" results from the fact that the inclined sectors of the protective riny are arranged by and in accordance with the tangential force component of the spring tension. The tangential force component of the spring tension is achieved if in the individual sectors - which are aligned along the periphery - the one end of the bore ~31 9~ 76~
or recess for the spring has a greater distance from t~e sheath area of the metal shaft than the other and of the bore or recess in question.
This sector adjustment can be observed particularly if the inner sheath areas of the sectors are smaller than the outer sheath~areas resulting theoreticall~ from the circular division. The result is a protective ring which, if properly mounted t has splits between the sectors. These splits become wider towards the inside. ~he sectors are arranged in such a way that wedge-like splits are formed between the sectors.
As mentioned before, these splits always open up towards the inside and are closQd on the outside, even if the diameter decreases.
For the adjustment process described above it is useful that the sectors have a plane inner sheath area so that they can move and align themselves accordingly on the sheath area of the metal shaft. The outer sheath areas of the sectors may also be plane and need not have a cylindrical shape. In addition, the imler as well as the outer sheath area of the sectors may have suitable profilesO
In order to avoid the heating of sprinys, particularly of springs closed in peripheral direction, on account of potential parasitic currents, it may be useEul to build at least one electrically insulating connection element into the springu Such a connection element may e.g. consist of highly sintered aluminium oxide.
The same consideration may be the reason for the incorporation of electrically insulating elements between the abuttillg surfaces of the sectors. This applies above all to abutting surfaces in peripheral direction. A~utting surfaces in ~ ~2 ~ ~
axial direction may also be kept at a distance by mean~ of electrically insulating elements.
If form locking connections are used~ it will be advantageous to design the connection elements as -sliding connections the sliding direction of which is parallel to the axis of the metal shat of the electrode holder. In this way it is possible to move the moldings or individua~
sectors either up or down in the simple way described so that partly damaged rings or sectors can be exchanged without causing extensive assembly work or the use of an excessive number of spare or replacement rings or sectors.
In the concrete case the positive sliding connection mentioned is designed as dovetail guide. This dovetail guide is not only mechanically solid but also enables the user to slide the sectors in a simple manner against the sheath area of the metal shaft of the electrode holder.
The grooves of the dovetail guides are located on the inner sheath areas of the sectors, while the contact strips are mounted on the sheath area of the metal shaft. This location of grooves on the inner sheath area of the sectors is advantageous because the loss of the relatively expensive sector material, which is extremely resistant to thermal and mechanical stress, is kept to a min;ml1m.
For reasons of expediency, the contact strips are separate components which are fastened to the sheath area of the metal shaft by riveting, bolting, welding or a similar method.
This is helpful not only in saving material for the metal shaft of the electrode holder but also in mounting the contact strips on relatively thin~wall~d metal shafts.
The cooled metal shaft of the electrode holder usually consists of copper, which is very expensive so that material savings are really decisive. Moreover, the metal shaft or the pipes making up the metal shaft which are intended for the cooling agent and the current supply, have to have relatively thin walls in order to obtain a cooling efficiency that is optimal for the entire unit.
If the protective jacket consists of several rings that are made up of sectors, it may be practical to place one one-piece ring between any two rings consisting o sectors.
As a result, the carrying capacity of the protective jacket may be further enhanced.
In accordanc~ with another embodiment of the invention the contact strips are interrupted in axial direckion of the metal shaft, with the distance between two aligned contact strip sections being not greater than the twofold axial height of a sector in this region. In this way it is possible to remove damaged or worn sectors and replace them by new ones even in the middle 20ne of the protectivP
jacket without having to remo~e the sectors above or below.
This also helps to reduce assembly time.
Furthermore~ it is advantageous if the contact strip sections are grouped in rings and if the contact strips of one group and the contact strips of the axially neighbouring yroup are staggered in peripheral direction. This results in a sector arrangement that is staggered ring by ring, which leads to a further increase in the mechanical stability of the protective jacket.
If that embodiment of the invention is used where at least one one-piece ring is part of the protective jacket, it is recommended that at the place where the ring is to be mounted the axial distance between two neighbouring groups of contact strips be somewhat greater than the axial height of the one~piece ring. The ring may then be turned at this place so that its grooves and the contact strips of the neighbouring groups are offset, which results in the ring being arrested in axial direction. Thus the ring serves as a support for all sectors or rings consisting of sectors that are located above the ring. If, therefore, the sectors below the ring break off partly or completely, the sectors above the ring are prevented from slipping along. This means that a large part of the metal shaft of the electrode holder r~ma; n.~ protected by undamaged sectors, even if the protec-tive jacket is damaged considerably. In this way it is possible to keep the damage to a minimum.
Sectors and/or one-piece rings should consist of non-graphitic or partly graphitic materials containing carbon. As a consequence, the life time of protective rings will be satisfactory from the economic point of view. A further advantage of the carbon cont~ining material relates to its favourable properties as far as slag or metal splashes are concerned. If the protective rings have the proper dimensions, the oxidation o~ carbon will proceed as slowly as desired~ especially on the hotter peripheral areas of the rings, thus preventing the troublesome accumulation of slag or metal parts that is requently observed on ceramic coatings.
The solution in accordance with the invention guarantees an excellent heat transfer from the protective jacket to the metal shaft. It is, thexe~ore, recommended that materials of low thermal conductivity be used for the pro-tective jacket.
Among the materials cont~; ni ng carbon the so-called non-graphitic or partly graphi~ic materials are especially suitable for this purpose.
I the user intends to do without the advan-tage of self-purification of the protective ring surface, ceramic materials may also be employed.
Depending on the respective requirements the material of the protective jacket may vary, i.e. materials con~Ain;ng carbon as well as ceramic materials may be used for both sectors and one-piece rings. It is favourable to use ceramic materials where the sectors of the upper section o-f the metal shaft are con~erned, and materials cont~;ning carbon where the lower section is concerned. Other solutions such as a mixed arrangement of rings or sectors of different materials are also possible.
When connecting the moldings located between metal shaft and clamping jaws in accordance with the invention, it is preferable to use a form loc~ing connection which is supported by resilient clamping.
For this purpose axially directed pairs of rails are affixed to the metal shaft the shape of which renders it possible to keep the axially directed rims or edges of the moldings between the rail parts projecting from the metal shaft and the metal shaft proper.
Therefore, the rails are characteri~ed by a section adjacent to the metal shaft, a section leading away from it~ and a section that is parallel to the metal shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
Some embodiments of the electrode holder are illustrated in the accompanying figures in which Figure 1 is a schematic full-view illustration of an electrode with an electrode holder in accordance with the invention, Figure 2 ls an illustration of a hollow cylinder sector several of which make up the protective jacket of the ~8~
electrode holder in accordance with the invention, Figure 3 is a sec~ional view of a par~ial ring consisting o~ several sectors, Figure 4 is a projection of such a partial ring, Figure 5 is an illustration of the assembly of the protective jacket of the electrode holde.r in accordance with the invention, with the ring being made up of sectors that con~ist of several partial rings, Figure 6 is an illustration of a possible type of connection of the springs connecting the sectors which then form a ring or a partial ring, Figure 7 is an illustration of another embodLment of the se tors, Figure 8 is a perspe~tive view of the sectors as lllustrated in Figure 7, Figures 9 to 11 are illustrations of possible axial connections of rings consisting of sector~, Figures 12, and 13 are illustrations of further ~bodiment~
of sectors, Flgure 14 is an illustration of another possibility of joining springs which then form a spring ring, Figure 15 ~s an axial sectional view o~ an electrode with an electrode holder in accordance with the invention, Figure 16 is a radial secti.onal view of the electrode a~ shown in Figure 15 along the intersection line XVI~XVI, Figure 17 is an illustration of the metal shaft of the electrode holder with paxtly omitted protective jacket to show the distribution of contact strips on the sheath area of the metal sha~t, Figure 18 is a radial sectional view of the electrode as illustrated in Figure 17 along the intersection line XVIII--XVIII, Figure 19 is a perspective view of a sector several of which form the protective jacket of the electrode. holder in accordance with the invention, Figure 20 is a perspective view of a one-piece ring intended for use in a protective jacket of an electrode holder in accordance with the invention, Figure 21 is a modified embodiment of a sector for the protective jacket of an electrode holder in accordan~e with the invention, Figure 22 is a further embodiment of a sector for the protective jacket of an electrode holder iIl accordance with the invention, Figure 23 is an illustration of the metal shaft with three moldings which are arranged between metal shaft and clamping jaws and which are fastened by~means of form locking rails.
7~
DETAILED DESCRIPTION OF THE DE~AWINGS
Figure 1 is a schematic illustration of the basic structure of a combination electrode for electric arc furnaces. This electrode comprises an electrode holder that is formed by a cooled metal shaft 1. An active part 2 of consumable material, e.g. graphite, is attached by means of a threaded nipple 3 to the lower tip of the metal shaft 1 constituting the electrode holder. The electrode is held by a supporting structure 4 affixed to the upper section oE the metal shaft I of the electrode holder. Figure 1 is a schematic illustration only, the electrical components and cooling elements are not shown, as they may be of the conventional type. The only part that is important in connection with the invention is the hollow cylindrical protective jacket 5 of temperature-resistant material which surrounds that section of the metal shaft 1 which remains within the furnace, thus protecting it from excessive thermal and mechanica stres~.
The protective jack~t 5 is made up of hollow cylinder sectors 10 as shown in Figure 2. The hollow cylinder sector has an inner 11 and an outer sheath area 12, two abutting surfaces in peripheral direction 13l and two faces in axial direction 14. In addition, the sector has two bores 15 which are located on one chord.
Figures 3 and 4 clearly show ho~ several s~ctors 10 form a partial ring by joining their abutting surfaces 13. The sectors 10 of this partial ring are connected by springs which pass through the bores 15~ In the figure the springs shown are spiral springs 20. Fork-like clamping elements 21 guarantee that the spiral springs 20 are secured at the end, thus prestressing them. These elements 21 hook on counter stops located at the end of the springs 20 or ~l76V
on their windings, thus keeping the springs 20 in a prestressed position.
Figure 4 illustrates on the left how the clamping elements 21 are fastened, while on the right of the illustration they are already arrested.
Figure 5 shows how partial rings, which consist of sectors lo, are joined,thus forming a complete ring. The partial rings are successively joined by connecting the respective tips of the springs 20 which are kept in a prestressed position by clamping elements 21. Upon the removal of the clamping elements 21 the abutting surfaces of the sectors rest snugly on each other also at the places where the partial rings join.
Such a ring, which is made up of sectors 10, may either be slid on the metal shaft 1 from one end or may be radially mounted ~n the metal shaf~-t in the w~y described by joining partial rings.
Th~ decisive criterion is that the rings, which consist of sectors 10, rest directly and with prestress on the sheath area of the metal shaft 1, as can be seen in Figure 1. This results in the advantages alxeady described, namely A good heat transfer between the protective jacket 5 and the metal shaft 1, less wear and tear due to oxidation, and the complete lack o~ detrimental tensions within the protective ring which-may result from a di:Eferent ~hPr~l expansion of the protective ring and the metal shaft or from radial temperature gradients within the protective ring.
Figure 6 illustrates a further possible type of connection of two springs connected in series 20 which, on the one hand, help to connect the sectors 10 among each other in the way described and which, on the other, are helpful _ 20 in mounting a ring consisting of sectors 20 with a certain prestress on the metal shaft 1. As shown in Figure 6, the tips of the springs 20 are equipped with stops 22 for the respective recesses 16 at the ends of the sector bores 15, with the respective spring 20 bracing the respective sectors 10 and at the same tirne pressing the entire ring, which consists of sectors 10, in assembly position with prestress against the sheath area of the metal shaft 1.
Figures 7 and 8 show a ~urther embodiment of thP sectors 10.
According to this embodiment, the abutting surfaces 13 of the respective sectors 10 which lie in periPheral direction, have at least one complementarY qraduation 17 in radial direction which engages in the way illustrated. In this case the metal shaft 1 is always safely protected, even if the abutting surfaces 13 of neighbouring sectors 10 do not snugly rest on each other, thus forming a split between the individual sectors 10 that is covered by the graduations 17~ Small splits between the individual sectors may be observed in the assembly position whenever the outside diameter of the metal shaft 1 is greater than specified and/or the inside diameter of the ring, consisting of sectors 10, of the protective jacket 5 is smaller than specified.
Figure. 9 illustrates a possible way in which the rings which consist of sectors 10 can be axially joined, if the protective jacket consists of several rings made up of sectors 10. In this case the faces 14 of the individual sectors 10 have grooves 18 in peripheral direction which are intended for the joining rings 19. As a result, there is also a tight connection between the faces 14 of the sectors 10 of neighbouring rings.
Figure 10 shows a further possibility of how the springs 20 may be fastened in the sectors 10. According to this embodiment the faces 14 of the sectors 10 have recesses 15a in peripheral direction which accommodate the springs 20 6~D
in a similar way as the bores 15 do. The recesses 15a may also act as grooves 18 required in the embodiment according to Figure 9.
Figure 11 is an illustration of a sector 10 whose axially directed faces and/or abutting surfaces 14 have a complementary radial graduation 17a. This graduation enables neighbouring sectors 10 to be positively joined in axial direction. If the faces and/or abutting surfaces 14 of neighbouring sectors 10 do not snugly fit over the entire area, the resulting split is covered by these graduations 17a. As a result, the metal shaft 1 will always be safely protected. Furthermore, by joining the sectors 10 in a positive manner, the protective jacket 5 will be even more resistant from the mechanical point of view.
It is, of course, possible to graduate the peripheral abutting surfaces 13 as well as the axially directed abutting surfaces 14 of each se~tor in order to brace the entire structure of sectors, which constitutes the protective jacket, not only in a form locking bu~ a1so in a resilient manner.
Figure 12 and Figure 13 show further embodiments of a protective ring for an electrode in accordance with the invention. According to these embodimentsl the width of the individual sectors 10 measured in peripheral direction is relatively small so that a large number of sectors is required for one protective ring. The sides 11 and 12 may be plane. Furthermore, the shape of the sectcrs 10 may be such that their abutting surfaces 13 and the radial beam 30a and/or 30b of the hollow cylinder form an angle or two angles oC and/or ~ of different sizes. The inner sheath areas 11 of the sectors 10 may be smaller than the outer sheath areas 12 calculated on the basis of a circular division.
3'7~
The invention relates to electrode holders for electric arc furnaces comprising a water-cooled metal shaft and a working part of consumable material, with the metal sha~t being, at least partly, surrounded by moldings of high-temperature resis-tant material.
BACKGROUND OF THE INVENTION
Electrodes with electrode holders of the type mentioned are available in two basic designs. According to the first design the electrode consists of two axially aligned sections, i.e.
the electrode holder, which constitutes the upper section, comprising a cooled metal shaft, a,nd, at its lower tip, the active part of consumable material where the electric arc is produced. This type of electxode is generally known as combination electrode. With the second type of design, the active part of consumable material is axially movable within the electrode holder which basically comprises a cooled metal shaft. The active part of consumable material consumed at its lower tip may, therefore, be compensated for by axial movement. This type of electrode is generally known as conventional feed through electrode. A common criterion of both designs is that the electrode holder, i.e. the li~uid-cooled metal shaft, during operation projects, at least partly, into the interior of the furnace.
However~ electrodes for electric arc furnaces are exposed to high thermal and mechanical stress. Thermal stress conditions result from the hiqh working temperatures reached particularly in the production of electric steel. Mechanical 7~
stress ls caused e.g. when the el~ctrode, upon its insertion inko the furnace, hit~ scrap material, or it may also result from movements of ~he moL~en metal or scrap material, or from vibrations caused by the electric arc.
In order to ensure th~ usefulness of these electrode~ it is, therefore, imperative to effectively protect the cooled metal shaft of the electrode holder, which during operation is in the interior of the furnace, against th~ thermal and mechanical stress me~tioned. Numerous solutions have been offered to this proble~.
The electrode holder of the combinakion electrodes described in BE-PS 867 876 takes the for~ of a metal shaft which contains the cooling syst~m and which is covered with a high-temperature resistant coating on the outside. In order to improve the adhesive capacity of this coating on the sl~eath area, the metal ~haft has hooks holding the coating in place.
Similar combination electrodes are described in GB-PS 1 223 162.
Their electrode holder is completely covered with a protective, ceramic coating. With this type of solution, attention has to be paid to the thickness of the ceramic coating, which should be as small as possible, and to the extent of lts application, which should include the electrode holder proper to ensure the insulation of its pipes. These pipes serve not o~ly as cooling water ducts but also aR current supply to the active part of graphlte~
~heEuropean patent application 0 010 305 published April 30, 1980 (U.S. Patent 4,291,190 is equivalent~ describes a combin-ation electrode with an electrode holder comprising a mekal shaft ~hich is electrically insulated against the current-carrying cooling system and which can be sufficiently cooled by a high-temperature resistant material between the cooling sys-tem and the metal shaft. The lower section of the metal shaft, ~3~'7~
which constitutes the electrode holder, is covered with a ceramic coat that is also secured by hooks.
The combination electrode of DE-AS 27 25 537 has a metallic~
liquid-cooled upper section constituting the elec-trode holder, which is insulated by a high-temperature resistant material covering thermally conductive pro~ections. The purpose of these projections is to prevent a direct mechanical contact with the line system if, as a result of high local stress~ the high-temperature resistant material is locally damaged by rigid scrap material. At the same time these projections act as a kind of fusep thereby preventing excessive currents from passing.
Finally, DE-AS 27 30 884 describes a conventional feed-through electrode whose cooled metal shaft, which constitutes the electrode holder and serves as passage through which the active part of graphite is fed, is covered with high-temperature resistant ma-terial. At the same time the metal shat has projections directed radially towards the outside which fasten the high-temperature resistant material. Thlese projections, which are distributed along the periphexy and in axial direction as evenly as possible, are designed to ensure a more constant cooling and better adhesive capacity of the high-temperature resistant material. This solution corresponds to the protec-tive coat designs mentioned in connection with combination electrodes. According to the most recent state of technology, the same solutions are offered for the electrode holders of combination electrodes and conventional elec-trodes.
All these electrode holders have one disadvantage in common, i.e. that the protective jacket, even if it is only slightly locally damaged, has to be removed from the metal shaft of the electrode holder and a new protective jacket has to be applied,which causes lengthy interruptions and high costs.
A further disadvantage of conventional electrode holders is the formation of slag and mekal layers on the protective jacket of ceramic material, which leads to disorders in furnace operation.
It was, therefore, suggested to create an electrode holder whose cooled metal shaft is protected by rings of a material containing carbon, preferably graphite. Electrode holders of this type have been employed and the protective jacket mentioned has proved extremely useful. The graphite rings act as an excellent protective coat from the mechanical as well as the thermal viewpoint. One advantage of such a protective jacket is that, i it is partly damaged, the graphite ring in question may be exchanged, while complete removal of the jacket is only required if continuous protective coatings are used. A further advantage is that the formation of slag or metal layers is avoided, for due to the destruction of the graphite surface by oxidation they keep falling off the protective jacket. One disadvantage is, however, that in some cases the rings show a certain tendency towards cracking which is caused by the different thermal expansion of the protective jacket and the metal shaft constituting the electrode holder, and, consequently, by the resulting tensions within the protective ring.
Furthermore, there is one problem that all electrode holders described have in common~, namely, how the metal parts can be fastened above the furnace lid. In general, this is achieved by means of clamping devices. Considering such factors as easy handling or ~uality of electric contact it is advantageous to use the mechanical clamp also as a means of current transferO As a consequence, graphite or carbon moldings are usually used between the metallic part of the electrode and the clamping jaws of a bearer arm, for these moldings combine favourable current transfer properties with good mechanical and therma:L properties.
However, the way how these moldings are to be fastened to the electrodes poses problems, as the moldings may break due to the clamping forces required. This may, in turn, lead to the loss of the moldings when, in varying the place of clamping e.g., t~e clamps have to be re~loved.
OBJECT OF THE INVENTION
The object of the presen-t invention is to create a protective jacket for the cooled metal shaft of electrode holders of the type mentioned which fully meets all thermal, mechanical, and electrical requirements, which has a design as simple as possible, which can be easily mounted and repaired, and which guarantees a good heat transfer to the cooled metal shaft of the electrode holder in order to improve the service life of the pro-tective jacket.
With regard to the electrode holder in question, this problem is solved by the connection of moldings to the metal shaft and/or among each other in a removable manner by means of form locking and/or resilie~tconnection elements.
The solution in accordance with the invention provides a protective jacket that meets all electrical, thermal, and mechanical requirements. I~ a ~resilient connection i5 used, the prestress of the individual moldings of the protective jacket makes them rest snugly on -the metal shaft of the electroda holder, which results in a good heat transfer between protective jacket and metal shaft over the entire area. This good heat transfer is achieved without inserting any filling material between the protective jacket and the metal shaft of the electrode holder~ In addition, on account of the~ resilient connection of the sectors, the individual moldings are capable of balancing tensions caused by the different thermal expansion of the material of the protective jacket on the one hand and the material of the metal shaft of the electrode holder on the other. Thus r there is no danger of the protective jacket belng damaged by this thermal expansion. The protective jacket is, therefore, in a position to meet all thermal requirements.
The s~me holds true for mechanical stress. By connecting the sectors in accordance with the inventionl i.e.among each other or to the metal part, it is possible to balance the production tolerances of the moldings so that their inner sheath area is always snuyly pressed against the sheath area of the metal shaft of the electrode holder.
In this way, compressive and bending ~orces are transferred from the protective jacket to the metal shaft of the electrode holder without any excessive strain on the material of the protective jacket as a result of insufficient contact between protective jacket and metal shat. At the same time, the metal shaft of the electrode holder is also protected by the moldings. Finally, depending on the requir~ments, the moldings are easy to mount or dismount. For this purpose, individual moldings or groups of r~oldings may be axially moved along the metal part. It is e.g. possible to connect several moldings or sectors which then form a partial ring, or to connect several partia:L rings which then form one complete ring. This means that a protective ring may be directly mounted on the metal shaft of the electrode holder. If one or several sectors of the protective ring are damaged, the damaged sector may simply be exchanged.
If the protective iacket consists of several rings each of which is made up of sectors, the ring at the lower tip of the metal shaft of the electrode holder which :is, of course, exposed to the highest strain within the furnace and, therefore, more likely to be damaged or worn than the rings arranged further to the top, should be removed first. It should be replaced by either a new ring or a ring used in the upper section of the metal shaft that is still suitable for the lower section. In this way it is possible to replace the rings successively, to reduce assembly time, and to cut the main~enance costs for the protective jacket of the electrode holder.
Advantageous designs of the electrode holder in accordance with the invention result Erom other claims as wellD
According to one version the sectors may consist of non-graphitic or partly graphitic materials containing caxbon.
This results in economical service times of the protective rings, while the properties of the carbon material with regard to slag or metal splashes are also favourable. If the dimensions of the protective rings are correct, the desired slow oxidation of carbon will be achieved especially on the hotter exterior peripheral areas of the rings, which prevents the accumulation of slag or metal parts, a disadvantage frequently observed when ceramic coatings are used.
Since the solution in accordance with the invention offers an ex~ellent heat transfer from the protective jacket to the metal shaft of the electrode holder, it is recommended that the protective jacket be made of materials that have a low thermal conductivity. Among the materials con~; n; ng carbon, the so-called non-graphitic or partly graphitic materials are, therefore, especially suitable.
If the user can do without the advantage of self-purification of the surface of the protective ring, céramic materials may also be used.
It is useful to use ceramic materials for the sectors in the upper section of the metal shaft of the electrode holder, and materials conta-ning carbon for the sectors in the lower section. Othex solutions, such as a mixed arrangement of rings or sectors of different materials, are also possible.
It is certainly an advantage that the non-positive connection of the sectors among each other and the formation of prestress,which enables the ring consisting of sectors to snugly rest on the metal shaft of the electrode holder, are achieved by spring power.
As far as the arrangement of the springs producing the spring power is concerned, there are a number of possibilities.
Each protective ring may have on~ or several spring rings, with each sp~ing ring being formed either by one spring or by several springs connected in series.
The springs are located in sector bores or recesses which are concentric to the ring. In this way the springs are incorporated in the sectors, which is a great advantage because they are protected against excessive thermal and mechanical stress.
In order to further reduce the ~herm~l strain on the springs, the bores or recesses are located near the inner sheath area of the sectors, which means that the springs and the cooling system of the metal shalt are as near as possible to each other so that the temperature in the spring zone is kept as low as possible.
The springs used may be spiral springs or leaf springs.
It is of special importance that the springs consist of a non-magnetic material in order to avoid the heating r~
of the springs as a result of hysteresis losses.
Basically r the springs should be characterized by a high heat resistance. For this reason the springs may be made of austenitic chrome-nickel-molybdenum steels or of material containing berylliumO
In accordance with another preferred embodiment of the invention, the abutting surfaces of neighbouring sectors, which lie in peripheral and/or axial direction, have at least one complementary radial graduation. Even i the abutting surfaces of neighbouring sectors do not snugly fit due to tolerances, these interlocking graduations guarantee that the sectors are well sealed, which, in turn, results in a safe protection of the cooled metal shaft of the electrode holder.
According to another embodiment the width of the sectors measured in peripheral direction is relatively small,with the abutting surfaces and the radial beam of the hollow cylinder forming an angle. This means that in relation to the respective radii the relatively thin sectors of a ring rest in an oblique manner on the metal shaft. Thus tolerances are balanced as a result of the so-called l'effect of self-adjustment", with the sectors adjusting thems~lves in a more vertical or a more horizontal position depending on the diameter of the metal shaft and/or the inside diameter of the sector ring.
This "e~fect of self-adj~stment" results from the fact that the inclined sectors of the protective riny are arranged by and in accordance with the tangential force component of the spring tension. The tangential force component of the spring tension is achieved if in the individual sectors - which are aligned along the periphery - the one end of the bore ~31 9~ 76~
or recess for the spring has a greater distance from t~e sheath area of the metal shaft than the other and of the bore or recess in question.
This sector adjustment can be observed particularly if the inner sheath areas of the sectors are smaller than the outer sheath~areas resulting theoreticall~ from the circular division. The result is a protective ring which, if properly mounted t has splits between the sectors. These splits become wider towards the inside. ~he sectors are arranged in such a way that wedge-like splits are formed between the sectors.
As mentioned before, these splits always open up towards the inside and are closQd on the outside, even if the diameter decreases.
For the adjustment process described above it is useful that the sectors have a plane inner sheath area so that they can move and align themselves accordingly on the sheath area of the metal shaft. The outer sheath areas of the sectors may also be plane and need not have a cylindrical shape. In addition, the imler as well as the outer sheath area of the sectors may have suitable profilesO
In order to avoid the heating of sprinys, particularly of springs closed in peripheral direction, on account of potential parasitic currents, it may be useEul to build at least one electrically insulating connection element into the springu Such a connection element may e.g. consist of highly sintered aluminium oxide.
The same consideration may be the reason for the incorporation of electrically insulating elements between the abuttillg surfaces of the sectors. This applies above all to abutting surfaces in peripheral direction. A~utting surfaces in ~ ~2 ~ ~
axial direction may also be kept at a distance by mean~ of electrically insulating elements.
If form locking connections are used~ it will be advantageous to design the connection elements as -sliding connections the sliding direction of which is parallel to the axis of the metal shat of the electrode holder. In this way it is possible to move the moldings or individua~
sectors either up or down in the simple way described so that partly damaged rings or sectors can be exchanged without causing extensive assembly work or the use of an excessive number of spare or replacement rings or sectors.
In the concrete case the positive sliding connection mentioned is designed as dovetail guide. This dovetail guide is not only mechanically solid but also enables the user to slide the sectors in a simple manner against the sheath area of the metal shaft of the electrode holder.
The grooves of the dovetail guides are located on the inner sheath areas of the sectors, while the contact strips are mounted on the sheath area of the metal shaft. This location of grooves on the inner sheath area of the sectors is advantageous because the loss of the relatively expensive sector material, which is extremely resistant to thermal and mechanical stress, is kept to a min;ml1m.
For reasons of expediency, the contact strips are separate components which are fastened to the sheath area of the metal shaft by riveting, bolting, welding or a similar method.
This is helpful not only in saving material for the metal shaft of the electrode holder but also in mounting the contact strips on relatively thin~wall~d metal shafts.
The cooled metal shaft of the electrode holder usually consists of copper, which is very expensive so that material savings are really decisive. Moreover, the metal shaft or the pipes making up the metal shaft which are intended for the cooling agent and the current supply, have to have relatively thin walls in order to obtain a cooling efficiency that is optimal for the entire unit.
If the protective jacket consists of several rings that are made up of sectors, it may be practical to place one one-piece ring between any two rings consisting o sectors.
As a result, the carrying capacity of the protective jacket may be further enhanced.
In accordanc~ with another embodiment of the invention the contact strips are interrupted in axial direckion of the metal shaft, with the distance between two aligned contact strip sections being not greater than the twofold axial height of a sector in this region. In this way it is possible to remove damaged or worn sectors and replace them by new ones even in the middle 20ne of the protectivP
jacket without having to remo~e the sectors above or below.
This also helps to reduce assembly time.
Furthermore~ it is advantageous if the contact strip sections are grouped in rings and if the contact strips of one group and the contact strips of the axially neighbouring yroup are staggered in peripheral direction. This results in a sector arrangement that is staggered ring by ring, which leads to a further increase in the mechanical stability of the protective jacket.
If that embodiment of the invention is used where at least one one-piece ring is part of the protective jacket, it is recommended that at the place where the ring is to be mounted the axial distance between two neighbouring groups of contact strips be somewhat greater than the axial height of the one~piece ring. The ring may then be turned at this place so that its grooves and the contact strips of the neighbouring groups are offset, which results in the ring being arrested in axial direction. Thus the ring serves as a support for all sectors or rings consisting of sectors that are located above the ring. If, therefore, the sectors below the ring break off partly or completely, the sectors above the ring are prevented from slipping along. This means that a large part of the metal shaft of the electrode holder r~ma; n.~ protected by undamaged sectors, even if the protec-tive jacket is damaged considerably. In this way it is possible to keep the damage to a minimum.
Sectors and/or one-piece rings should consist of non-graphitic or partly graphitic materials containing carbon. As a consequence, the life time of protective rings will be satisfactory from the economic point of view. A further advantage of the carbon cont~ining material relates to its favourable properties as far as slag or metal splashes are concerned. If the protective rings have the proper dimensions, the oxidation o~ carbon will proceed as slowly as desired~ especially on the hotter peripheral areas of the rings, thus preventing the troublesome accumulation of slag or metal parts that is requently observed on ceramic coatings.
The solution in accordance with the invention guarantees an excellent heat transfer from the protective jacket to the metal shaft. It is, thexe~ore, recommended that materials of low thermal conductivity be used for the pro-tective jacket.
Among the materials cont~; ni ng carbon the so-called non-graphitic or partly graphi~ic materials are especially suitable for this purpose.
I the user intends to do without the advan-tage of self-purification of the protective ring surface, ceramic materials may also be employed.
Depending on the respective requirements the material of the protective jacket may vary, i.e. materials con~Ain;ng carbon as well as ceramic materials may be used for both sectors and one-piece rings. It is favourable to use ceramic materials where the sectors of the upper section o-f the metal shaft are con~erned, and materials cont~;ning carbon where the lower section is concerned. Other solutions such as a mixed arrangement of rings or sectors of different materials are also possible.
When connecting the moldings located between metal shaft and clamping jaws in accordance with the invention, it is preferable to use a form loc~ing connection which is supported by resilient clamping.
For this purpose axially directed pairs of rails are affixed to the metal shaft the shape of which renders it possible to keep the axially directed rims or edges of the moldings between the rail parts projecting from the metal shaft and the metal shaft proper.
Therefore, the rails are characteri~ed by a section adjacent to the metal shaft, a section leading away from it~ and a section that is parallel to the metal shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
Some embodiments of the electrode holder are illustrated in the accompanying figures in which Figure 1 is a schematic full-view illustration of an electrode with an electrode holder in accordance with the invention, Figure 2 ls an illustration of a hollow cylinder sector several of which make up the protective jacket of the ~8~
electrode holder in accordance with the invention, Figure 3 is a sec~ional view of a par~ial ring consisting o~ several sectors, Figure 4 is a projection of such a partial ring, Figure 5 is an illustration of the assembly of the protective jacket of the electrode holde.r in accordance with the invention, with the ring being made up of sectors that con~ist of several partial rings, Figure 6 is an illustration of a possible type of connection of the springs connecting the sectors which then form a ring or a partial ring, Figure 7 is an illustration of another embodLment of the se tors, Figure 8 is a perspe~tive view of the sectors as lllustrated in Figure 7, Figures 9 to 11 are illustrations of possible axial connections of rings consisting of sector~, Figures 12, and 13 are illustrations of further ~bodiment~
of sectors, Flgure 14 is an illustration of another possibility of joining springs which then form a spring ring, Figure 15 ~s an axial sectional view o~ an electrode with an electrode holder in accordance with the invention, Figure 16 is a radial secti.onal view of the electrode a~ shown in Figure 15 along the intersection line XVI~XVI, Figure 17 is an illustration of the metal shaft of the electrode holder with paxtly omitted protective jacket to show the distribution of contact strips on the sheath area of the metal sha~t, Figure 18 is a radial sectional view of the electrode as illustrated in Figure 17 along the intersection line XVIII--XVIII, Figure 19 is a perspective view of a sector several of which form the protective jacket of the electrode. holder in accordance with the invention, Figure 20 is a perspective view of a one-piece ring intended for use in a protective jacket of an electrode holder in accordance with the invention, Figure 21 is a modified embodiment of a sector for the protective jacket of an electrode holder in accordan~e with the invention, Figure 22 is a further embodiment of a sector for the protective jacket of an electrode holder iIl accordance with the invention, Figure 23 is an illustration of the metal shaft with three moldings which are arranged between metal shaft and clamping jaws and which are fastened by~means of form locking rails.
7~
DETAILED DESCRIPTION OF THE DE~AWINGS
Figure 1 is a schematic illustration of the basic structure of a combination electrode for electric arc furnaces. This electrode comprises an electrode holder that is formed by a cooled metal shaft 1. An active part 2 of consumable material, e.g. graphite, is attached by means of a threaded nipple 3 to the lower tip of the metal shaft 1 constituting the electrode holder. The electrode is held by a supporting structure 4 affixed to the upper section oE the metal shaft I of the electrode holder. Figure 1 is a schematic illustration only, the electrical components and cooling elements are not shown, as they may be of the conventional type. The only part that is important in connection with the invention is the hollow cylindrical protective jacket 5 of temperature-resistant material which surrounds that section of the metal shaft 1 which remains within the furnace, thus protecting it from excessive thermal and mechanica stres~.
The protective jack~t 5 is made up of hollow cylinder sectors 10 as shown in Figure 2. The hollow cylinder sector has an inner 11 and an outer sheath area 12, two abutting surfaces in peripheral direction 13l and two faces in axial direction 14. In addition, the sector has two bores 15 which are located on one chord.
Figures 3 and 4 clearly show ho~ several s~ctors 10 form a partial ring by joining their abutting surfaces 13. The sectors 10 of this partial ring are connected by springs which pass through the bores 15~ In the figure the springs shown are spiral springs 20. Fork-like clamping elements 21 guarantee that the spiral springs 20 are secured at the end, thus prestressing them. These elements 21 hook on counter stops located at the end of the springs 20 or ~l76V
on their windings, thus keeping the springs 20 in a prestressed position.
Figure 4 illustrates on the left how the clamping elements 21 are fastened, while on the right of the illustration they are already arrested.
Figure 5 shows how partial rings, which consist of sectors lo, are joined,thus forming a complete ring. The partial rings are successively joined by connecting the respective tips of the springs 20 which are kept in a prestressed position by clamping elements 21. Upon the removal of the clamping elements 21 the abutting surfaces of the sectors rest snugly on each other also at the places where the partial rings join.
Such a ring, which is made up of sectors 10, may either be slid on the metal shaft 1 from one end or may be radially mounted ~n the metal shaf~-t in the w~y described by joining partial rings.
Th~ decisive criterion is that the rings, which consist of sectors 10, rest directly and with prestress on the sheath area of the metal shaft 1, as can be seen in Figure 1. This results in the advantages alxeady described, namely A good heat transfer between the protective jacket 5 and the metal shaft 1, less wear and tear due to oxidation, and the complete lack o~ detrimental tensions within the protective ring which-may result from a di:Eferent ~hPr~l expansion of the protective ring and the metal shaft or from radial temperature gradients within the protective ring.
Figure 6 illustrates a further possible type of connection of two springs connected in series 20 which, on the one hand, help to connect the sectors 10 among each other in the way described and which, on the other, are helpful _ 20 in mounting a ring consisting of sectors 20 with a certain prestress on the metal shaft 1. As shown in Figure 6, the tips of the springs 20 are equipped with stops 22 for the respective recesses 16 at the ends of the sector bores 15, with the respective spring 20 bracing the respective sectors 10 and at the same tirne pressing the entire ring, which consists of sectors 10, in assembly position with prestress against the sheath area of the metal shaft 1.
Figures 7 and 8 show a ~urther embodiment of thP sectors 10.
According to this embodiment, the abutting surfaces 13 of the respective sectors 10 which lie in periPheral direction, have at least one complementarY qraduation 17 in radial direction which engages in the way illustrated. In this case the metal shaft 1 is always safely protected, even if the abutting surfaces 13 of neighbouring sectors 10 do not snugly rest on each other, thus forming a split between the individual sectors 10 that is covered by the graduations 17~ Small splits between the individual sectors may be observed in the assembly position whenever the outside diameter of the metal shaft 1 is greater than specified and/or the inside diameter of the ring, consisting of sectors 10, of the protective jacket 5 is smaller than specified.
Figure. 9 illustrates a possible way in which the rings which consist of sectors 10 can be axially joined, if the protective jacket consists of several rings made up of sectors 10. In this case the faces 14 of the individual sectors 10 have grooves 18 in peripheral direction which are intended for the joining rings 19. As a result, there is also a tight connection between the faces 14 of the sectors 10 of neighbouring rings.
Figure 10 shows a further possibility of how the springs 20 may be fastened in the sectors 10. According to this embodiment the faces 14 of the sectors 10 have recesses 15a in peripheral direction which accommodate the springs 20 6~D
in a similar way as the bores 15 do. The recesses 15a may also act as grooves 18 required in the embodiment according to Figure 9.
Figure 11 is an illustration of a sector 10 whose axially directed faces and/or abutting surfaces 14 have a complementary radial graduation 17a. This graduation enables neighbouring sectors 10 to be positively joined in axial direction. If the faces and/or abutting surfaces 14 of neighbouring sectors 10 do not snugly fit over the entire area, the resulting split is covered by these graduations 17a. As a result, the metal shaft 1 will always be safely protected. Furthermore, by joining the sectors 10 in a positive manner, the protective jacket 5 will be even more resistant from the mechanical point of view.
It is, of course, possible to graduate the peripheral abutting surfaces 13 as well as the axially directed abutting surfaces 14 of each se~tor in order to brace the entire structure of sectors, which constitutes the protective jacket, not only in a form locking bu~ a1so in a resilient manner.
Figure 12 and Figure 13 show further embodiments of a protective ring for an electrode in accordance with the invention. According to these embodimentsl the width of the individual sectors 10 measured in peripheral direction is relatively small so that a large number of sectors is required for one protective ring. The sides 11 and 12 may be plane. Furthermore, the shape of the sectcrs 10 may be such that their abutting surfaces 13 and the radial beam 30a and/or 30b of the hollow cylinder form an angle or two angles oC and/or ~ of different sizes. The inner sheath areas 11 of the sectors 10 may be smaller than the outer sheath areas 12 calculated on the basis of a circular division.
3'7~
- 2~ -As a result, wedge-like splits 40, which become wider towards the interior, will show between the abuttiny surfaces 13 of the assembled protective ring that rests with prestress on the metal shaft 1. The tangential force component of the spring tension presses the sectors 10, which join in an oblique manner and which have smaller inner sheath areas 11J
in such a manner against the metal shaft 1 that the wedge-shaped splits 40 are always closed on the outside. This effect makes it possible to balance tolerances on the outside diameter of the metal shaft 1 and/or on the inside diameter of the ring made up of sectors 10. But even if the sector areas 12 are attacked by oxidation, the wedge-like splits will basically remain closed on the outside.
As is shown in Figure 12, the bores 15 are not located on the chord of an ideal cylinder sector but they are rather at an angle to this chord. This means for each sector that the distance between the sheath area of the metal shaft 1 and one tip of the bore 15 is greater than the distance between the sheath area of the metal shaft 1 and the other tip of the bore, with the respective tips having the same peripheral direction. In this way the tangential force component results from the spring tension which causes the "effect of self-adjustment" described earlier.
In order to prevent the spring which is closed in peripheral direction from being heated by possible parasitic currents, it may be useful to build at least one electrically insulating connection element into the spring. This embodiment is shown in Figure 14, where the electrically insulating connection element 50 is used for the connection of two springs 20. The electrically insulating connection element 50 may e.g. be made of highly sintered aluminium oxide.
t7~
The same consideration m~y play a role if electrically insulating elements, e.y. of asbestos, are inserted between the abutting surfaces of the ~ectors. This type of embodiment is not illustrated. This solution is recommended especially for abutting surfaces 13 in peripheral direction, it may, however, also be used for faces and/or abutting surfaces 14 in axial direction.
Figure 1S is again a schematic illustration of ~he basic structure of a combination electrode for electric arc furnaces. This electrode comprises a cooled metal shat 51 constituting the electrode holder. An active part 52 of consumable material, e.g. graphite, is attached to the lower tip of the metal shaft 51 by means of a threaded nipple 53. The electrode is held by a supporting structure 54 located in the upper section of the metal shaft 51 of the electrode holder. Since Figure 15 is a schematic illustration only, the electrical components and cooling elements of the electrode holder are not included, as these components may have a conventional design. What is important in connection with the invention is a protective jacket 55 in the form of a hollow cylinder that consists of one of the temperature-resistant rnaterials mentioned. This jacket surrounds the metal shaft 51 of the electrode holder along the section located within the furnace, thus protecting it in the way described against detrimental thermal and mechanical stressO
The protective jacket 55 is made up of hollow cylinder sectors.
One of them is shown in the perspective illustration of Figure 19. The hollow cylinder sector 60 has an inner sheath area 61 and an outer sheath area 62, two abutting surfaces 63 in peripheral direction, and two faces 64 in axial direction~
A number of such sectors 60 make up a ring. Several rings consistiny of such sectors 60 form the protective jacket 65.
7~
The sectors 60 and ~he sheath area of the cooled metal shaft 51 are joined by means of positive connection elements. In the concrete case these positive connection elements are dovetail guides. Basically, there are two possible designs.
According to Figures 15 and 16 the grooves 65a run in axial direction over the sheath area of the metal shaft 51~ i.e.
they are cut into the sheath area, while the corresponding contact strips 60a run over the inner sheath area 61 of the respective sectors 60. If this embodiment is used, the grooves 51a run continuously over the entire length of the metal shaft 51, which simplifies the manufacture of the metal shaf-t 51. However, in this case the sectors can be slid on the metal shaft 51 only from one end.
If the embodiment according to Figures 17 and 18 is used, the contact strips of the dovetail guides are located on the sheath area o the metal shaft 51. They are divided into contact strip sections 72 which are grouped in rings 73 taking up at least one ring, preferably,however, two or more rings consisting of sectors 60.
The individual contact strip sections 72 are riveted or bolted 74 to the sheath area of the metal sha~t 51 and are thus removable, if required.
The axial distance 75 between two groups 73 and 73' of contact strip sections 72 is not greater than the twofold axial height of the sectors 60 to be arranged in this region.
As a rule, it is rec~mm~n~d to have an axial distance 75 that is somewhat greater than the axial height of the sectors 60 to be arranged in this region. In the area where the contact strips are interrupted it is thus possible to slip the sectors 60 on the individual contact strip sections 72 so that damaged or worn sectors can be exchanged in the middle 20ne of the protective jacket 55 without having to remove all sectors above and below.
It has proved useful to place a one-piece ring at certain intervals between the ring-shaped groups. Such a ona-piece ring 80 is shown in Figure 20. The inner sheath area 81 of such a ring 80 has grooves 82 which correspond or are complementary to the contact strip sections 72. Such a ring will, of course, be placed between two groups 73' and 73"
of contact strips 72. For this purpose the axial distance 76 between these two groups 73' and 73" of contact strip sections 72 is somewhat greater than the axial height of the ring 80. In this way the ring 80 may be moved from one end of the metal shaft 51 to the zone of interruption 76 and turned in such a way that the grooves 82 and the contact strip sections 72 of group 73~i and, if necessary, also those of group 73' are staggered. In this way the one-piece rlng 80 will be firmly secured in axial direction elther against the bottom or against both sides. If the sectors arranged below the ring 80 break under certain extreme conditions, the sectors arranged above the ring 80 are safely held by the ring 80. As a consequence, any damage of the protective jacket 55 or of the metal shaft 51 is kept to a minimum.
The group-wise staggering OL the contact strips 72, which was described earlier, serves the same purpose, since it prevents the sectors above from slipping down in case of a complete braakdown of the sectors below. An additional advantage of the groupwise staggering of the contact strip sections 72 is that the abutting surfaces 6C of the sectors 63 are also staggered groupwise, which further increases the solidity of the protective jacket 55.
Although the measures described help not only to obtain a snug connection between the inner sheath area 60 of the sectors 61 and the sheath area of the metal shaft but also guarantee that the abutting surfaces of neighbouring sectors rest snugly on each other, the latter may be improved even more. Such an improvement is shown in Figure 21. The abutting 7~
surfaces of two neighbouring-sectors 60, wh:ich lie in peripheral direction 63, have a complementary radial graduation. As shown in Figure l5, these complementary graduations 66 of two neighbouring sectors 60 engage. This mea~s that eve~ if there is a split between two neighbouring sectors 60, this split will be covered by the graduations 660 ~s a result, the metal shaft 51 will nevertheless be safely protected.
Figure 22 shows that the axially directed abutting surfaces and/or faces 64 of the sectors 60 of two axially neighbouring rings may have radial complementary graduations that guarantee the safe cover of these areas even if greater tolerances are involved.
Another possibility are ring-shaped coverings between the faces of axially neiqhbourinq sectors which rest on the correspondinq periPheral qrooves in the sector faces, thus guaranteeing the desired safe cover of possible splits.
Figure 23 illustrates a cross section of tha upper part of an electrode holderD On the outside wall of the metal shaft 91 there are three graphite moldings 92 which are held by rails 94. Clamping jaws 93 are pressed against the electrode holder which is thus secured in a certain axial position.
The graphite moldings 92 may be distributed along the periphery in an even or uneven manner, they may have, but need not have, the same size as far as their length on the periphery is concerned, but they should have the same thickness. The rails ~4 are affixed to the metal part 91 by suitable bolts. As the graphite moldings occasionally have to be exchanged, bolting is more practical than a fixed connection such as welding.
7~
The rails are shaped in such a way that they encompass the graphite moldings at their axial edges in such a m~nnPr that they are held against the metal part 91 without tension, for in view of ~he strong clamping forces of the clamping jaws 93 an excessive prestress would be highly unfavourable.
In order to be able to fulfill this holding function, the rails 94 are designed in such a way that one part 96 rests directly on the metal part 91, one part 97 leads away from the metal part, and one part 98 runs at a certain distance parallel to the metal part. This distance 99 is basically identical with the thickness of the graphite moldings.
in such a manner against the metal shaft 1 that the wedge-shaped splits 40 are always closed on the outside. This effect makes it possible to balance tolerances on the outside diameter of the metal shaft 1 and/or on the inside diameter of the ring made up of sectors 10. But even if the sector areas 12 are attacked by oxidation, the wedge-like splits will basically remain closed on the outside.
As is shown in Figure 12, the bores 15 are not located on the chord of an ideal cylinder sector but they are rather at an angle to this chord. This means for each sector that the distance between the sheath area of the metal shaft 1 and one tip of the bore 15 is greater than the distance between the sheath area of the metal shaft 1 and the other tip of the bore, with the respective tips having the same peripheral direction. In this way the tangential force component results from the spring tension which causes the "effect of self-adjustment" described earlier.
In order to prevent the spring which is closed in peripheral direction from being heated by possible parasitic currents, it may be useful to build at least one electrically insulating connection element into the spring. This embodiment is shown in Figure 14, where the electrically insulating connection element 50 is used for the connection of two springs 20. The electrically insulating connection element 50 may e.g. be made of highly sintered aluminium oxide.
t7~
The same consideration m~y play a role if electrically insulating elements, e.y. of asbestos, are inserted between the abutting surfaces of the ~ectors. This type of embodiment is not illustrated. This solution is recommended especially for abutting surfaces 13 in peripheral direction, it may, however, also be used for faces and/or abutting surfaces 14 in axial direction.
Figure 1S is again a schematic illustration of ~he basic structure of a combination electrode for electric arc furnaces. This electrode comprises a cooled metal shat 51 constituting the electrode holder. An active part 52 of consumable material, e.g. graphite, is attached to the lower tip of the metal shaft 51 by means of a threaded nipple 53. The electrode is held by a supporting structure 54 located in the upper section of the metal shaft 51 of the electrode holder. Since Figure 15 is a schematic illustration only, the electrical components and cooling elements of the electrode holder are not included, as these components may have a conventional design. What is important in connection with the invention is a protective jacket 55 in the form of a hollow cylinder that consists of one of the temperature-resistant rnaterials mentioned. This jacket surrounds the metal shaft 51 of the electrode holder along the section located within the furnace, thus protecting it in the way described against detrimental thermal and mechanical stressO
The protective jacket 55 is made up of hollow cylinder sectors.
One of them is shown in the perspective illustration of Figure 19. The hollow cylinder sector 60 has an inner sheath area 61 and an outer sheath area 62, two abutting surfaces 63 in peripheral direction, and two faces 64 in axial direction~
A number of such sectors 60 make up a ring. Several rings consistiny of such sectors 60 form the protective jacket 65.
7~
The sectors 60 and ~he sheath area of the cooled metal shaft 51 are joined by means of positive connection elements. In the concrete case these positive connection elements are dovetail guides. Basically, there are two possible designs.
According to Figures 15 and 16 the grooves 65a run in axial direction over the sheath area of the metal shaft 51~ i.e.
they are cut into the sheath area, while the corresponding contact strips 60a run over the inner sheath area 61 of the respective sectors 60. If this embodiment is used, the grooves 51a run continuously over the entire length of the metal shaft 51, which simplifies the manufacture of the metal shaf-t 51. However, in this case the sectors can be slid on the metal shaft 51 only from one end.
If the embodiment according to Figures 17 and 18 is used, the contact strips of the dovetail guides are located on the sheath area o the metal shaft 51. They are divided into contact strip sections 72 which are grouped in rings 73 taking up at least one ring, preferably,however, two or more rings consisting of sectors 60.
The individual contact strip sections 72 are riveted or bolted 74 to the sheath area of the metal sha~t 51 and are thus removable, if required.
The axial distance 75 between two groups 73 and 73' of contact strip sections 72 is not greater than the twofold axial height of the sectors 60 to be arranged in this region.
As a rule, it is rec~mm~n~d to have an axial distance 75 that is somewhat greater than the axial height of the sectors 60 to be arranged in this region. In the area where the contact strips are interrupted it is thus possible to slip the sectors 60 on the individual contact strip sections 72 so that damaged or worn sectors can be exchanged in the middle 20ne of the protective jacket 55 without having to remove all sectors above and below.
It has proved useful to place a one-piece ring at certain intervals between the ring-shaped groups. Such a ona-piece ring 80 is shown in Figure 20. The inner sheath area 81 of such a ring 80 has grooves 82 which correspond or are complementary to the contact strip sections 72. Such a ring will, of course, be placed between two groups 73' and 73"
of contact strips 72. For this purpose the axial distance 76 between these two groups 73' and 73" of contact strip sections 72 is somewhat greater than the axial height of the ring 80. In this way the ring 80 may be moved from one end of the metal shaft 51 to the zone of interruption 76 and turned in such a way that the grooves 82 and the contact strip sections 72 of group 73~i and, if necessary, also those of group 73' are staggered. In this way the one-piece rlng 80 will be firmly secured in axial direction elther against the bottom or against both sides. If the sectors arranged below the ring 80 break under certain extreme conditions, the sectors arranged above the ring 80 are safely held by the ring 80. As a consequence, any damage of the protective jacket 55 or of the metal shaft 51 is kept to a minimum.
The group-wise staggering OL the contact strips 72, which was described earlier, serves the same purpose, since it prevents the sectors above from slipping down in case of a complete braakdown of the sectors below. An additional advantage of the groupwise staggering of the contact strip sections 72 is that the abutting surfaces 6C of the sectors 63 are also staggered groupwise, which further increases the solidity of the protective jacket 55.
Although the measures described help not only to obtain a snug connection between the inner sheath area 60 of the sectors 61 and the sheath area of the metal shaft but also guarantee that the abutting surfaces of neighbouring sectors rest snugly on each other, the latter may be improved even more. Such an improvement is shown in Figure 21. The abutting 7~
surfaces of two neighbouring-sectors 60, wh:ich lie in peripheral direction 63, have a complementary radial graduation. As shown in Figure l5, these complementary graduations 66 of two neighbouring sectors 60 engage. This mea~s that eve~ if there is a split between two neighbouring sectors 60, this split will be covered by the graduations 660 ~s a result, the metal shaft 51 will nevertheless be safely protected.
Figure 22 shows that the axially directed abutting surfaces and/or faces 64 of the sectors 60 of two axially neighbouring rings may have radial complementary graduations that guarantee the safe cover of these areas even if greater tolerances are involved.
Another possibility are ring-shaped coverings between the faces of axially neiqhbourinq sectors which rest on the correspondinq periPheral qrooves in the sector faces, thus guaranteeing the desired safe cover of possible splits.
Figure 23 illustrates a cross section of tha upper part of an electrode holderD On the outside wall of the metal shaft 91 there are three graphite moldings 92 which are held by rails 94. Clamping jaws 93 are pressed against the electrode holder which is thus secured in a certain axial position.
The graphite moldings 92 may be distributed along the periphery in an even or uneven manner, they may have, but need not have, the same size as far as their length on the periphery is concerned, but they should have the same thickness. The rails ~4 are affixed to the metal part 91 by suitable bolts. As the graphite moldings occasionally have to be exchanged, bolting is more practical than a fixed connection such as welding.
7~
The rails are shaped in such a way that they encompass the graphite moldings at their axial edges in such a m~nnPr that they are held against the metal part 91 without tension, for in view of ~he strong clamping forces of the clamping jaws 93 an excessive prestress would be highly unfavourable.
In order to be able to fulfill this holding function, the rails 94 are designed in such a way that one part 96 rests directly on the metal part 91, one part 97 leads away from the metal part, and one part 98 runs at a certain distance parallel to the metal part. This distance 99 is basically identical with the thickness of the graphite moldings.
Claims (43)
1. Electrode holder for electric arc furnaces comprising a water-cooled metal shaft and a working part of consumable material, the metal shaft being at least partly surrounded by moldings of high temperature resistant material, characterized in that the moldings are connected to the metal shaft and/or among each other in a removable manner by form locking and/or resilient fastening means.
2. Electrode holder according to claim 1 wherein said moldings form a protective jacket, surrounding essentially that part of the electrode holder which is located within the furnace or a region provided for the clamping of the electrode holder.
3. Electrode holder according to claim 2 wherein said protective jacket consists of at least one ring made up of several hollow cylinder sectors which are connected in a resilient way and which, with prestress, rest directly on the metal shaft.
4. Electrode holder according to claim 3 wherein said sectors preferably consist of non-graphitic and/or partly graphitic materials containing carbon.
5. Electrode holder according to claim 3 wherein said sectors consist of ceramic materials.
6. Electrode holder according to claims 4 and 5 wherein the sectors in the upper region of the electrode holder consist of ceramic materials, while the sectors in the lower region are made of materials containing carbon.
7. Electrode holder according to claim 3 wherein said sectors are connected by spring power.
8. Electrode holder according to claim 7 wherein each sector ring has one or several spring ring(s), each spring ring comprising one spring or several springs connected in series.
9. Electrode holder according to claim 7 wherein said springs are arranged in sector, bores or sector recesses located in an essentially concentric manner to the ring.
10. Electrode holder according to claim 9 wherein said bores or recesses are located near the inner sheath area of said sectors.
11. Electrode holder according to claim 8 wherein said springs are spiral springs.
12. Electrode holder according to claim 8 wherein said springs are leaf springs.
13. Electrode holder as according to claim 8 wherein said springs consist of a non-magnetic material.
14. Electrode holder according to claim 8 wherein said springs consist of a high-temperature resistant material.
15. Electrode holder according to claims 13 and 14 wherein said spring consist of austenitic chrome-nickel-molybdenum steels.
16. Electrode holder according to claim 13 wherein said springs consist of a material containing beryllium.
17. Electrode holder according to claim 3 wherein the abutting surfaces of neighbouring sectors, which are located in peripheral and/or axial direction, have at least one complementary radial graduation.
18. Electrode holder according to claim 3 wherein the inner sheath area of the sectors is even.
19. Electrode holder according to claim 3 wherein the outer sheath area of the sectors is even.
20. Electrode holder according to claim 3 wherein the width of the sectors measured in peripheral direction is relatively small.
21. Electrode holder according to claim 17 wherein one or both abutting surfaces of the sectors and the radial beam of the hollow cylinder form an angle (d;B).
22. Electrode holder according to claim 20 wherein the two abutting surfaces of the sectors and the radial beam of the hollow cylinder form angles (d;B) of different sizes.
23. Electrode holder according to claim 3 wherein the inner sheath areas of the sectors are smaller than the outer sheath areas resulting theoretically from a circular division, which is the reason why the fully mounted protective ring between the sectors is characterized by wedge-shaped splits which become wider towards the inside.
24 . Electrode holder according to claim 17 wherein the slant sectors of the protective ring due to the tangential force component of the spring tension are arranged in such a way that wedge-shaped splits which open up towards the inside and which are closed outside are formed between the sectors,
25. Electrode holder according to claim 24 wherein said slant sectors keep the wedge-shaped splits closed on the outside, even if the outside diameter of the mounted protective ring decreases e.g. as a result of oxidation.
26. Electrode holder according to claim 3 wherein at least one electrically insulating connection element is incorporated in the spring closed in peripheral direction.
27. Electrode holder according to claim 17 wherein electrically insulating elements are inserted in between the abutting surfaces of the sectors.
28. Electrode holder according to claim 3 wherein said moldings or hollow cylinder sectors are removably mounted on the sheath area of the metal shaft by means of form locking connection elements.
29. Electrode holder according to claim 28 wherein said form locking connection elements are sliding connectors which allow the displacement of the sectors in a direction of the metal shaft.
30. Electrode holder according to claim 29 wherein said sectors are connected to the sheath area of the metal shaft by means of dovetail guides.
31. Electrode holder according to claim 30 wherein the groove of the dovetail guides are located on the inner sheath areas of the sectors, while the contact strips are situated on the sheath area of the metal shaft.
32. Electrode holder according to claim 31 wherein said contact strips are separate elements which are connected to the sheath area of the metal shaft by riveting, bolting, welding or a similar method.
33. Electrode holder according to claim 2 wherein said protective jacket consists of several rings made up of sectors, characterized in that there is always one one-piece ring between any two rings consisting of sectors.
34. Electrode holder according to claim 32 wherein said contact strips are interrupted in the axial direction of the metal shaft, with the distance between two aligned contact strip sections being smaller than the twofold axial height of the sectors to be arranged in this region,
35. Electrode holder according to claim 32 wherein said contact strips are arranged in ring-shaped groups, whereby the contact strips of one group and the contact strips of the axially neighbouring group are staggered in peripheral direction.
36. Electrode holder according to claim 35 wherein at least one one-piece ring is part of the protective jacket, and wherein at the place where the one-piece ring is to be mounted the axial distance between 2 neighhouring groups of contact strips is greater than the axial height of the one-piece ring.
37. Electrode holder according to claim 36 wherein said abutting surfaces of neighbouring sectors, which lie in peripheral and/or axial direction, have at least one complementary radial graduation.
38. Electrode holder according to claim 36 wherein said sectors and/or said one-piece rings consist of non-graphitic or partly graphitic materials containing carbon.
39. Electrode holder according to claim 37 wherein said sectors and/or said one-piece rings consist of ceramic materials.
40. Electrode holder according to claim 28 wherein said positive connection elements consist of rails encompassing the moldings and their axial edges.
41. Electrode holder according to claim 40 wherein said rails hold the moldings against the metal shaft without prestress.
42. Electrode holder according to claim 41 wherein said rails comprise one part adjacent to the metal shaft one part leading away from the metal shaft and one part at which is parallel to and set off a distance from the metal shaft.
43. Electrode holder according to claim 42 wherein said distance essentially corresponds to the thickness of the moldings.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3144520 | 1981-11-09 | ||
| DEP3144437 | 1981-11-09 | ||
| DE19813144437 DE3144437A1 (en) | 1981-11-09 | 1981-11-09 | Electrode holder for an arc furnace |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1198760A true CA1198760A (en) | 1985-12-31 |
Family
ID=6145954
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000415103A Expired CA1198760A (en) | 1981-11-09 | 1982-11-08 | Electrode holder for arc furnaces |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS58126694A (en) |
| CA (1) | CA1198760A (en) |
| DE (1) | DE3144437A1 (en) |
| RO (1) | RO89746A (en) |
| ZA (1) | ZA828211B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| USD804555S1 (en) | 2015-09-28 | 2017-12-05 | Carl Townsend | Welding electrode holder |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102013101488B3 (en) * | 2013-02-14 | 2014-02-06 | Connex Gmbh | Method for producing an electrode attachment |
| FI125874B (en) | 2013-08-27 | 2016-03-15 | Outotec Oyj | Pressure ring assembly for contact shoes in an electrode system |
-
1981
- 1981-11-09 DE DE19813144437 patent/DE3144437A1/en not_active Withdrawn
-
1982
- 1982-11-08 CA CA000415103A patent/CA1198760A/en not_active Expired
- 1982-11-09 JP JP57197413A patent/JPS58126694A/en active Pending
- 1982-11-09 ZA ZA828211A patent/ZA828211B/en unknown
- 1982-11-09 RO RO82109003A patent/RO89746A/en unknown
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| USD804555S1 (en) | 2015-09-28 | 2017-12-05 | Carl Townsend | Welding electrode holder |
| US10259069B2 (en) | 2015-09-28 | 2019-04-16 | Carl Townsend | Welding electrode holder |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58126694A (en) | 1983-07-28 |
| DE3144437A1 (en) | 1983-06-09 |
| ZA828211B (en) | 1983-09-28 |
| RO89746A (en) | 1986-07-30 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |