MX2008008957A - Threaded pin, carbon electrode, and electrode assembly - Google Patents

Abstract

The invention relates to a to carbon electrodes having at least one socket with an internal thread to be mated with a threaded pin having at least one external thread and to such threaded pin for connecting such carbon electrodes, wherein said internal thread or external thread is provided with non-load bearing abutment thread windings. Further, the invention relates to an electrode assembly with a threaded connection, comprising an electrode and a pin.

Description

THREADED PIN, CARBON ELECTRODE, AND ELECTRODE ASSEMBLY TECHNICAL FIELD The invention relates to a threaded pin for connecting carbon electrodes having at least one adapter bushing with an internal thread, said pin having a central axis running along of its length, two ends, a middle plane lying between said two ends and at least one external thread. Furthermore, the invention relates to a carbon electrode having at least one adapter sleeve with an internal thread for coupling with a threaded pin. In addition, the invention relates to an electrode assembly with a threaded connection, comprising an electrode and a pin. BACKGROUND ART Carbon electrodes, especially graphite electrodes, are used in the steel industry to melt metals in electrothermal furnaces such as electric arc furnaces, where electrical current is passed through the electrode in an arc between the electrode and the metal to generate the heat needed to melt the metal. The electric arc and the high temperatures in the furnace, which can be up to 1500 ° C or even more, cause the lower end of the electrode, which extends into the furnace in close proximity to the molten metal, it is consumed slowly. Accordingly, a series of electrodes is generally joined to form a column electrodes which advances progressively in the furnace. To compensate for the shortening of the electrode column, more electrodes are screwed on the upper end of the column. The electrodes are attached to said columns via a pin (sometimes referred to as a connecting sleeve) that connects the ends of adjacent electrodes. The pin usually has the form of two opposite male threaded ends which may have a cylindrical or conical shape. The pin is screwed into the threaded coupling adapter sleeves provided at both ends of the electrodes. The pin is usually screwed firmly into one of the electrode adapter sleeves before sending it to a customer. To prevent loosening of the pin due to vibrations and the like, the pin must be screwed firmly into the adapter sleeve, without leaving any clearances between the flanks of the thread. This mounting of a threaded pin inside the electrode adapter bushing is usually referred to as a monotrode, and the adapter bushing with the pin is referred to as a monotrode adapter bushing or a pre-adjusted adapter bushing. For use in an oven, the adapter sleeve with monotrode it is attached to another electrode by screwing the protruding portion of the pin into its exposed adapter bushing to build a column. When a furnace is in use, currents in excess of 100,000 A as well as bending moments are repeatedly exerted on the electrode column due to the oscillation of the furnace tubing. The column is also subject to constant vibrations or impacts of the loading material, which can also place stress on the pin. The extreme mechanical, electrical and thermal stresses exerted on the pin can cause cracks in the pin and, more commonly, grooves in the upper monotrode adapter bushing, usually in the lower electrode column seal. These slits in the adapter sleeve with upper monotrode of the lower electrode column seals are due to the temperature gradients combined with the thermal expansion differentiation coefficients (CTE) of the pin and the electrode. This is especially true if the pin is screwed firmly into the adapter bushing for transportation. Because the surfaces of the threads of the pin and the adapter sleeve with monotrode are in full contact, the movement of the threads of the pin, relative to the threads of the adapter sleeve, is inhibited, andvice versa, leading to high internal tangential forces in the adapter bushing. This problem is exacerbated, particularly as the juncture approaches the hot metal bath in an oven, where the temperature gradients are higher. To avoid these undesired effects, the pin can be slightly unscrewed from the adapter sleeve with a monotrode such that the threads are not completely engaged. In this constellation, only half of the surfaces of the threads of the pin and the adapter sleeve with monotrode are in contact, possibly supporting the full load of the electrode column. To prevent the partially meshed pin from being completely unscrewed from the monotrode adapter bushing, plastic pins are usually inserted within the internal diameters extending from the surface of the electrode adapter bushing to the pin. Thus, the clearances between the internal threads of the adapter sleeve with monotrode and the external threads of the pin are provided to allow a different CTE growth of the pin with respect to the adapter sleeve with monotrode. However, the procedure for centering and fixing the pin inside an adapter bus before boarding the customer is difficult, time consuming, and highly dependent on the skill of the operator. Often also, during transportation, the plastic pins are not sufficient to restrict a connecting sleeve in a monotrode adapter bushing, and the thread damage may result. This damage can leave internal debris in the adapter sleeve with monotrode which prevents the correct tightening when the electrode is added to the oven. The loosening can then progress to the point where the contact of the end surface of the electrode to the electrode is lost, which leads to an increase in the electrical resistance of the connection. More electrical current is then channeled through the connection pin leading to localized superheat. As a result, the lower end of the electrode column can crack and fall into the molten steel, which interrupts the electric arc and ends the melting process. Alternatively, plastic or metal parts can be stuck on the threads of the pin and / or the adapter sleeve with monotrode. This process is usually referred to as "projection". The pin can then be screwed firmly into the adapter sleeve with monotrode for transport and it is not necessary to loosen the pin of the adapter sleeve with monotrode before connecting the pin with an additional electrode. In the oven, the material projection on the threads is fused such that the clearances are maintained between the internal threads of the adapter sleeve with monotrode and the external threads of the pin to allow different CTE growths of the pin and the adapter bushing with monotrode. However, it is difficult to mount the projection parts and it is difficult to obtain free spaces of defined dimensions. In addition, since the dimensions of the carbon electrodes and the connection pins for the electric arc furnaces are highly standardized to ensure the interchangeability of the electrodes and pins of several manufacturers, a solution is required that omits the changes of design for the electrodes and pins of the previous art. BRIEF DESCRIPTION OF THE INVENTION It is consequently an object of the invention to provide a threaded pin for the carbon electrodes, a carbon electrode and an electrode assembly with a threaded pin that overcomes the aforementioned disadvantages of the known devices and methods and which is Provide for a threaded connection that will prevent loosening and cracking. With the above and other objects in view, a threaded pin and an electrode are provided according to the invention. of carbon, which have thread coils of splicing that do not carry load integrated in their threads. Spliced thread coils that bear no load on the pin are provided for a defined splice to position the pin relative to an adapter sleeve of a prior art electrode. Also, splice thread windings that do not carry charge in the electrode adapter sleeve are provided for a defined splice to position a pin of the prior art with respect to the electrode adapter sleeve. Therefore, it is not possible to firmly screw a pin into an electrode such that the surfaces of the thread are in full contact. In addition, the thread splicing of the pin or the electrode contact the corresponding thread windings of a prior art electrode or pin of the prior art such that open open spaces are provided between the internal thread of the electrode and the external thread. of the passer. This prevents the threads of the pin from fully engaging the threads of the adapter bushing during placement in the finishing department prior to shipment of an adapter sleeve with monotrode. These open free spaces, which were previously only possible by special means, such as with the projection or fastening of the pin before mentioned, allow the growth CTE of the pin with respect to the adapter sleeve with monotrodo. Consequently, the presence of slots of the adapter sleeve in the threaded connection is reduced, which can lead to full length slits, body rupture, and loosening in the joint. In addition, an adapter sleeve with monotrode, ie a pin screwed into the adapter sleeve of an electrode, is still stable during transportation and handling since the forces exerted on the protrusion of the pin are sufficient to prevent loosening of the pin. In addition, the tangential stresses in the adapter sleeve with monotrode are lightened, which also helps to minimize the formation of indentations. Furthermore, this invention omits the design changes for the pins and electrodes of the prior art since a pin according to this invention can be used to connect (monotrode) electrodes of the prior art or an electrode according to this invention can be connected (monotrode) ) by pins of the previous art. When an electrode becomes monotroped by the insertion of a pin prior to shipping, it is known to measure a so-called "pin width projection". This is a measure of how deeply seated the pin is in the electrode adapter bushing; that is, how far projects out the pin of the adapter sleeve, measured from the flat end surface of the electrode with respect to a reference point on the pin using a pin width. This pin width projection is, at least indirectly, an indication of how far the pin will be inserted into a non-monotone adapter bushing when mounted in an electric arc furnace. The total distance that the pin will be inserted into the adapter sleeve without monotroping an electrode then depends on the tolerances of the adapter sleeve with monotrode, the tolerances of the end with monotrode of the pin, the tolerances of the end without monotrode of the pin and the tolerances of the bushing adapter without monotrode. Splicing thread coils that do not carry load on the thread of the pin or the electrode according to the present invention ensure that the monotrode end of the pin is only inserted a certain distance into the adapter sleeve with monotrode, and that there are clearances between the threads of the pin and the threads of the adapter sleeve. The pin width projection being exclusively determined by the splicing thread windings that do not carry the pin or electrode load consequently has a relatively small variation. Accordingly, the variation of the width projection of Pin can just be cut in half by the invention. In addition, the variation in the distance with which the monotrode end of the pin will be inserted into an adapter sleeve without monotroping in an electrode can be minimized (by half), likewise. The net result is that the variation of the joint of the assembled electrode is less than about half. In this application, the term "middle plane of the pin" is defined as the region where the two ends of the pin meet, without distinction of a possible different size of the two ends, that is, the median plane of the threaded pin is not necessarily the geometric center with respect to the total length or structure of the pin. In a preferred embodiment of the invention, at least one of said ends of the pin, preferably both ends, comprising said thread is / are conical in order to facilitate the screwing into the adapter sleeves of the electrode and to improve the coupling. Usually, the pin is provided with external bi-conical threads. In accordance with this invention, splice thread windings that bear no pin loading are provided at both ends of the pin in the area of the thread adjacent the middle plane of the pin. These splicing thread windings that do not carry load comprise up to 30% of the thread windings of each end of the pin. In accordance with a preferred embodiment of this invention, spliced thread coils that bear no pin load are provided on only one end of the pin. This end of the pin is the one designed to convert. in monotrode an electrode. In accordance with this invention, splice thread windings that do not carry electrode charge are provided on both electrode adapter sleeves in the area of the thread adjacent to the bottom of the adapter sleeve. These non-load-bearing splice coils comprise up to 30% of the thread windings in each adapter sleeve. According to a preferred embodiment of this invention, splicing thread coils that do not carry the electrode charge are provided only in an electrode adapter sleeve. This electrode adapter bushing is designed to be monotroped by a pin. According to a preferred embodiment of this invention, the splicing thread coil bearing no final charge is followed by a single thread coil having no contact to the coupling threads. This coil of thread that has no contact acts as a buffer zone between splice threads that do not carry a load and thread windings that carry a load (conventional) to prevent thermo-mechanical stress. The present invention is further directed to an electrode assembly with a threaded connection comprising an electrode made of a carbon material with an adapter sleeve having an internal thread, a bottom of the adapter sleeve and a central shaft running along the length of its length, with the assembly further comprising a pin made of a carbon material and having an external thread for connecting two electrodes, two ends and a central axis running along its length, where either said electrode or said pin have splice thread windings that carry no load on their threads, which, when the pin is screwed into the adapter sleeve, come into contact with the corresponding thread surfaces of the pin or coupling electrode before one of said ends of the pin reach the bottom of the corresponding adapter sleeve. This contact of the splicing thread windings that do not carry charge of the inventive electrode or pin with the corresponding (conventional) thread windings of the coupling electrode or pin coincides with the contact of the remaining (conventional) thread windings of the inventive electrode or pin with the corresponding (conventional) thread windings of the coupling pin or electrode, which eventually support the loading of the electrode column. Again, the defined splice of the pin and adapter sleeve before one end of the pin reaches the bottom of the adapter sleeve is provided for open spaces or gaps between the internal thread of the adapter sleeve and the external thread of the pin. These open open spaces in turn allow the CTE growth of the pin relative to the adapter sleeve with monotrode, thus minimizing the risk of cracks and the possibility of subsequent breaks in the pin, in the adapter sleeve, or in the body. It is preferred, do both; the electrode and the carbon pin or graphite synthetically produced. This material imparts the property of plastic deformation capacity. Therefore, the crests of a thread coil made of synthetically produced carbon or graphite do not simply break but can deform. This further minimizes the probability of slots in the pin or in the corresponding adapter bushing of an electrode. The internal thread of an electrode adapter sleeve and the external thread of a pin usually have windings of thread with a substantially uniform spacing, a root, a ridge and a substantially V-shaped profile. To provide an approximately equal part of the load transferred between the two thread windings, it is preferred that at least one of said internal threads and external is formed with a wedge slope in said root and that the ridges of at least the other of said internal and external threads splices with said wedge slopes, when said pin is screwed into said adapter bushing. In a conventional threaded connection, the upper thread winding usually carries the largest load on its flank. The thread coil immediately below is subjected to a lower load and the additional thread coils underneath have to withstand even lower loads. As a consequence, only a few thread windings participate in the transfer of the loads. These higher stresses in the first thread windings can cause pin slits and / or adapter bush. In contrast to that, when the crests of a thread coil join with the wedge slopes of the other thread coil, an approximately equal part of the load is transferred through all the thread coils. With the pin or the electrode provided with non-load-bearing splice coils in accordance with this invention, the aforementioned modified thread shape can be be used in the adapter with monotrode more easily, because the opposing forces ensure that the correct contact between the standard threads and wedge slopes is maintained during transportation, etc., before adding the electrode with monotrode to an electrode for form a column of electrodes. The invention will now be described in detail with reference to preferred embodiments and drawings. All the features described and / or illustrated in the drawings form the subject matter of the invention, independently of their inclusion or combination in the claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A / B shows a pin and a longitudinal section of an electrode before forming the monotrode (joining) Figure 2A / B shows a longitudinal section of two prior art electrodes joined by a prior art pin and a detailed view of the area of the joint Figure 3A / B shows a longitudinal section of two prior art electrodes joined by a pin according to the invention and a detailed view of the joint area Figure 4 shows a detailed longitudinal section of the adapter sleeve of an electrode according to the invention monotroped by a prior art pin Figure 5A / B shows a detailed longitudinal section of two different threaded connections between an electrode and a pin. In Figure 5A, the load vectors are drawn on the flanks of the thread windings, while in Figure 5B these load vectors are applied to the wedge slopes in the roots of the thread windings. Figure 6 shows a detailed longitudinal section of the adapter sleeve of an electrode of the prior art monotroped by a pin according to an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES In the drawings, electrodes 1, 2 are schematically represented, each having two ferrules 3 and 4 adapters. The electrodes 1, 2 are fixed coaxially by a connecting pin 5 being screwed into the sockets 3, 4 adapters. The electrodes 1, 2 and the connecting pin 5 are made of a carbon material, preferably graphite. Figure 1A and Figure IB provide an overview of the arrangements of an electrode 1 and a connection pin 5 before forming the monotrode. The sockets 3, 4 adapters arranged coaxially of the electrode 1 are recessed on both end surfaces 6 of the electrode. Each cap 3, 4 adapter has a bottom 7 of the cap adapter and is provided with internal threads 8 having thread coils 9 (conventional). The connecting pin 5 has external threads 10 and has flat end surfaces 11 on each side. The adapter sleeve 3 (lower) is also referred to as "adapter sleeve with monotrode" in the figures. The connecting pin 5 has the shape of two opposite male threaded ends 5a and 5b which can have an external conical thread (Figure IB) or cylindrical thread (Figure 1A). Consequently, the bushings 3, 4 adapters have a conical internal thread (Figure IB) or cylindrical thread (Figure 1A). The end 5a of the pin (upper) is also referred to as "pin end with monotrode" in the figures. The two ends 5 a, b of the pin are in the median plane M of the pin, without distinction of a possible different size of the two ends 5 a, b of the pin, that is, the median plane M of the threaded pin 5 is not necessarily the geometric center with respect to the total length or structure of the pin 5. Figure 2A shows the joint of an electrode column of the prior art consisting of electrodes 1, 2 joined together by the pin 5. The connecting pin 5 is a standard connection pin having two end portions 5a, 5b, conical, and a midplane lying between the two end portions. The external threads Conics are provided in each of the two end portions 5a, 5b, which mesh with the internal threads of the adapter bushings 3, 4. The electrode 1 was initially converted to monotrode with the pin 5 (prior art) by screwing the pin 5 with its end 5a threaded firmly into the adapter sleeve 3 for transportation. As shown in Figure 2B, both ends 5a, b of the pin are provided exclusively with standard (conventional) thread windings 13. The surfaces of the thread 10 of the pin at its threaded end 5a of the adapter sleeve 3 with monotrode are in full contact so that the growth CTE different from the pin 5 and the adapter sleeve 3 leads to cracks and other aforementioned problems. In addition, the median plane M of the pin is displaced and the pin width projection with respect to the end surface 6 of the monotrode adapter bushing 3 is reduced. Figure 3A shows the joint of an electrode column according to this invention consisting of the prior art electrodes 1, 2 joined together by a pin 5 according to this invention. The connection pin 5 is a standard connecting pin, with respect to its geometry, having two end portions 5a, 5b, conical, and a median plane M lying between the two portions of extreme. The external conical threads 10 are provided in each of the two end portions 5a, 5b, which mesh with the internal threads 8 of the adapter bushes 3, 4. The adapter sleeve 3 of the electrode 1 was initially converted into a monotrode by screwing the pin 5 with its end 5a threaded firmly to it. As shown in Figure 3B, the external thread 10 of the end 5b of the lower pin has exclusively standard (conventional) thread windings 13, while the end 5a of the upper pin (monotrode) is additionally equipped with spliced thread 14 windings. which do not bear load adjacent to the median plane M of the pin having face fitting surfaces 15 towards the end surface 11 of the pin. In accordance with this invention, the splice coils 14 that bear no load on the pin 5 are provided at both ends 5 a, b of the pin in the area of the thread adjacent to the median plane of the pin M. According to an embodiment Preferred of this invention (Figure 3B), splice thread windings 14 that bear no load on pin 5 are provided only at one end 5a of the pin. This end 5a of the pin is designed to convert an electrode 1, 2 into a monotrode.

The non-loaded splice coils 14 comprise up to 30% of the thread windings of one end 5 a, b of the pin, depending on the length of the pin 5 and the diameter of the electrode 1, 2. The windings 14 of The threads are molded and positioned in relation to the (conventional) thread windings 13 of the pin 5 such that they provide the splice surfaces 15 that bear no load that they buttress with the screw coils 9 of the adapter sleeve 3 with monotrode. This contact, which carries no load of the connecting screw windings 14 of the inventive pin 5 with the corresponding (conventional) thread 8 of the coupling electrode 1, coincides with the gear of the standard thread windings 13 of the inventive pin 5 with the windings 9. of the coupling electrode 1, which eventually support the loading of the electrode column. Thus, the free spaces 12 between the internal threads 8 of the monotrode adapter bushing 3 and the external threads 10 of the pin 5 are provided to allow different CTE growths of the pin 5 and the adapter bushing 3 with monotrode. The non-loaded splice coil windings 14 may have the same shape as the (conventional) thread coils 13 to simplify the process machining Other forms of the thread windings 14 that include the non-planar splice surfaces 14 are within the scope of this invention. It is, however, important that the non-splicing surfaces 16 of the thread coil 14 not be in contact with the thread 8 of the coupling electrode to provide a free space 12. It is a preferred embodiment of this invention that the non-loaded splice coils 14 are followed by a single thread coil 17 having no contact to the internal threads 8 of the monotrode adapter sleeve 3. This non-contacting thread coil 17 acts as a buffer zone between the non-loaded splice coils 14 and the (conventional) thread coils 13 to prevent thermo-mechanical stress. The thread coil 17 having no contact can have a shape similar to the thread coils 13 or 14, but somewhat reduced in size, to simplify machining. It can also be machined completely, that is, leaving a reserve space instead of a winding flank. As shown in Figure 3A, the position of the middle plane of the pin coincides according to this invention with the plane of the flat end surface 6 of the electrode 1 (monotrode) and, possibly, with the flat end surface 6 of the connected electrode 2. (without monotrode). The projection of pin width is thus correct and the free space 11 of the threaded joint between the internal thread 8 of the adapter sleeve 4 (without monotrode) of the electrode 2 and the external thread 10 of the end 5b of the pin of the pin 5 is provided to allow the CTE growth of the pin 5 within the ferrule 4 adapter of the electrode 2 without causing additional thermo-mechanical stresses on the pin or on the adapter sleeve. Figure 4 shows the adapter sleeve 3 of an electrode 1 according to the invention with monotrode with a pin 5 (conventional). The external thread 10 of both ends 5 a, b of the pin has exclusively threads 13 of standard thread (conventional). The monotrode adapter bushing 3 has standard (conventional) thread windings 9 and is additionally equipped with non-load-bearing splice windings 14 adjacent to the bottom 7 of the adapter bushing having face splice surfaces 15 toward the end surface 6 of the electrode. According to this invention, the splicing windings 14 that do not carry charge of the electrode 1, 2 are provided in both cylindrical 3, 4 adapters in the area of the thread adjacent the bottom 7 of the adapter sleeve. According to a preferred embodiment of this invention, the splicing windings 14 that do not carry electrode charge 1, 2 are provided only in an adapter sleeve 3. This bushing 3 adapter is the one designed to be monotroped by a pin 5 (conventional). The non-loaded splice coil windings 14 comprise up to 30% of the thread windings of an adapter sleeve 3, 4, depending on the length of the pin 5 and the diameter of the electrode 1, 2. As further shown in FIG. FIG. 4 shows the non-load-bearing contact of the connecting thread windings 14 of the inventive electrode 1 with the corresponding (conventional) thread 9 of the coupling electrode 1 coincides with the gear of the standard thread windings 13 of the pin 5 with the corresponding screw threads. thread coils 10 (conventional) of electrode 1, which eventually support the loading of the electrode column. In addition, the thread 9 of the electrode 1 is provided with a non-contacting thread coil 17 which acts as a buffer zone between the non-loaded splice coils 14 and the (conventional) thread coils 10 to prevent the thermo-mechanical effort. Figure 5 A, B illustrates the improved transfer of mechanical loads compared to a traditional threaded connection (Figure 5A) with a threaded connection between a electrode 1 and a pin 5 according to patent application EP 1 528 840 Al (Figure 5B). Particularly the load vectors drawn on the flanks of the screw coils 13 of the pin clarify the differences. The threads 8, 10 of the electrodes 1, 2 and the pin 5 have windings 9, 13 with substantially uniform spacing, a root, a ridge 19 and a substantially V-shaped profile. In the traditional threaded connection, see Figure 5A, the upper thread winding 13 has the longest load vector on its flank. The thread coil 13 immediately below is subjected to a smaller load vector, the thread coil 13 below that has an even smaller load, and so on. The screw coils 13 of the bottom barely participate in the transfer of the charges from the electrode 1 to the pin 5. According to EP 1 528 840, one of the threads 8, 10 is formed with the wedge slopes 18 at the root of the windings 9, 13 and the ridges 19 of the coupling thread windings 9, 13 connect with said wedge slopes 18 when the pin 5 is screwed into the adapter sleeve 3, 4. In the threaded connection between an electrode 1 and a pin 5 according to the patent application EP 1 528 840 Al, see Figure 5B, the load vectors drawn on the wedge slopes 18 at the roots of the windings 13 of Threads are of practically equal size for all 18 wedge slopes. This means that an approximately equal part of the load is transferred at each contact surface of the ridge 19 of the thread coil 9 of the electrode 1 to the wedge slope 18 at the root of the thread coil 13 of the pin 5. Figure 6 shows the socket 3 adapter of a monotrode conventional electrode 1 with a pin 5 having a thread 10 formed according to EP 1 528 840 A1 with wedge slopes 18 at the root of the windings 13 where the ridges 19 of the windings 9 The threaded coupling electrode splices with said wedge earrings 18 when the pin 5 is screwed into the adapter sleeve 3. According to this invention, the thread 10 also comprises windings 14 of splicing thread that bear no load and preferably a winding 17 of thread that has no contact. Therefore, it is shown that the invention can also be applied to new thread designs without being limited to traditional threads. KEY FOR THE FIGURES 1 electrode (upper) 2 electrode (lower) 3 adapter bush (with monotrode) 4 adapter bush (without monotrode) connection pin 5a end (with monotrode) of the pin 5 5b end of pin pin 5 6 end surface of electrode 7 bottom of adapter bushing 8 internal thread (adapter bushing) 9 screw threads of adapter bushing (conventional) 10 external thread (pin) 11 end surface of pin 12 head clearance Threaded joint 13 Thread coils (conventional) of pin 5 14 Thread coils for splicing of pin 5 15 Splicing surface of winding 13 Thread 16 Non-spliced surface of winding 13 Thread 17 Thread coil having no contact 18 Slope in wedge 19 Crest of the thread windings M middle plane of the pin

Claims (15)

1. CLAIMS 1. A threaded electrode (1, 2) with two end surfaces (6) of the electrode and two bushings (3, 4) adapters with a bottom (7) of the adapter sleeve and internal threads (8), said electrode (1, 2) having a central axis running along its length, characterized in that said internal thread (8) is provided with non-bearing splice coil windings (14) having splice surfaces (15) facing towards each other. the extreme surfaces (6) of the electrode. The electrode (1, 2) according to claim 1, characterized in that the internal thread (8) of only one of the two adapter sleeves (3, 4) is provided with windings (14) of splice thread that They do not carry cargo. The electrode (1, 2) according to claim 1 or 2, characterized in that up to 30% of the windings of the internal thread (8) are coiled thread windings (14) without load. The electrode (1, 2) according to one of claims 1 to 3, characterized in that the non-loaded splice coils (14) are provided in the area of the thread (8) adjacent to the bottom (7) of the adapter bushing. 5. A threaded pin (5), especially for connecting carbon electrodes (1, 2) having two ferrules (3, 4) adapters with an internal thread (8), said pin (5) characterized in that it has a central axis that runs along its length, two extreme surfaces (11), two portions (5a, 5b), a middle plane (M) lying in the middle of said two end portions (5a, 5b) and at least one thread (10) external, wherein said external thread (10) are provided with non-load bearing splice windings (14) having face splicing surfaces (15) toward the end surfaces (11) of the pin. The pin (5) according to claim 5, characterized in that the external thread (10) of only one of the two end portions (5a, 5b) is provided with windings (14) of splice threads that do not carry cargo. The pin (5) according to claims 5 or 6, characterized in that up to 30% of the thread windings (10) external are windings (14) of splicing thread that carry no load. The pin (5) according to one of claims 5 to 7, characterized in that the non-loaded splice coils (14) are provided in the area of the thread (10) adjacent to the median plane M of the passer. 9. The electrode (1, 2) or the pin (5) according to one of the preceding claims, characterized in that the Non-loaded splice coils (14) are followed by a coil (17) with no contact. 10. The electrode (1, 2) or the pin (5) according to one of the preceding claims, characterized in that the thread coils (9, 13) of the threads (8, 10) have a substantially uniform separation, a root , a ridge (19) and a substantially V-shaped profile, and wherein at least one of said internal and external threads (8, 10) is formed with a wedge slope (18) in said root, said crests (19). ) of at least the other of said internal and external threads (8, 10) spliced with said wedge slopes (18), when said pin (5) or electrode (1, 2) are screwed together. The electrode (1, 2) or the pin (5) according to one of the preceding claims, characterized in that said electrode (1, 2) or pin (5) are made of carbon or graphite. The electrode (1, 2) or the pin (5) according to one of the preceding claims, characterized in that the internal threads (8) and the external threads (10) have a conical shape. 13. A pre-installation of an electrode (1, 2) according to one of claims 1 to 4, 9 to 12, characterized in that the electrode (1, 2) is converted to monotrode with a pin (5) of the Previous art in a cap (3,4) adapter provided with non-loaded splice thread windings (14) and wherein the median plane (M) of the pin is aligned with the end surface (6) of the electrode in said bushing (3), 4) adapter. A pre-installation of a pin (5) according to one of claims 5 to 12, characterized in that one of the ferrules (3,4) adapters of an electrode (1, 2) of the prior art becomes monotrode with the end (5a, b) of the pin provided with non-loaded splice coils (14) and wherein the median plane (M) of the pin is aligned with the end surface (6) of the electrode in said bushing (3,4) adapter. 15. An electrode assembly, characterized in that it comprises pre-installations according to claims 13 or 14 of a pin (5) and an electrode (1, 2).