FR2682254A1 - Holding device for an electrode in an arc furnace - Google Patents

Abstract

The subject of the invention is an electrode holding device, especially for an electric arc furnace, comprising an electrode holder arm (1) fitted at its front end (11) with a clamp (3) for holding the electrode. The electrode holder arm (1) is extended beyond the electrode (E) by a hollow rigid piece (4) forming a support body for the clamp and comprising both an inner bearing part constituting at least a part of the fixed jaw (31) of the clamp and an outer bearing part (41) rigidly connected to the inner part, the moving jaw (32) being mounted horizontally sliding in the said support body (4) and the tightening member (5) being interposed between the moving jaw (32) and the outer bearing part (41).

Description

 The invention relates to an electrode holding device provided more specifically for an electric arc furnace.

 In general, an electric furnace used in particular in the metallurgical industry for the manufacture of steel by melting scrap, comprises a tank closed by a volte-shaped cover and in which one or more electrodes passing through corresponding holes in the boat. Each electrode is fixed to the end of an arm which extends in overhang above yours from a support mazot placed next to the tank.

 As the electrode is consumable, its height position relative to the arm must be adjustable. This is why the electrode-carrying arm is provided, at its front end, with means for holding the electrode in a vertical position allowing its progressive descent while ensuring its electrical supply.

 For this purpose, generally a clamp for holding the electrode in vertical position is used, comprising two jaws, respectively fixed and movable, associated with a clamping member for the electrode and the electrical supply to the electrode is ensured by at least one contact piece connected to a current source by at least one conductor.

 To allow the opening of the volte, the electrode is raised and then the electrode-holder arm is rotated around a vertical axis. In addition, the tank and, often, the mat and the electrode-holder arm are fixed on a platform which can be tilted slightly by tilting on rolling supports so as to pour the steel or the slag through suitable orifices provided in the side wall of the tank. This is why the electrode supply conductors generally comprise a first rigid part extending over the entire length of the electrode-carrying arm up to the support mat and a second flexible part connected to the current source and allowing the movements of rotation of the arm and tilting of the tank.

 The holding clamp must be provided to provide sliding and secure support for the electrode, as well as its electrical supply at extremely high currents. This is why the various parts constituting the clamp, in particular the two jaws and the clamping member, have relatively large dimensions.

 This is why, in the known arrangements, the assembly of the clamping members is placed on the side of the arm, often even inside of it, so that only the machotre placed on the other side of the the electrode is projecting from it.

 The applicant company was aware, however, that it could be interesting to modify the devices used until now for the maintenance of the electrode with the aim, in particular, of obtaining more reliable installations, more maintenance easy, and ensuring the power supply in better conditions.

 The invention therefore relates, in general, to an electrode holding device in an arc furnace comprising an electrode-carrying arm extending in a cantilever, substantially horizontally, between a rear end provided with fixing means on a support mast and a front end provided with support and electrical supply means for the electrode comprising an electrode holding clamp comprising two jaws, respectively fixed and movable, associated with a clamping member d '' an electrode interposed between said jaws, and means for electrically supplying the electrode comprising at least one contact piece applied to the electrode and connected to a current source by at least one first conductor extending along the electrode-carrying arm up to the support mast and extended by at least one second conductor extending from the support mast to the power source.

 In accordance with the invention, the electrode-carrying arm is extended beyond the electrode by a hollow rigid piece forming a support body for the clamp and comprising two support parts spaced from one another by a distance greater than the thickness of the electrode increased by the dimensions of the clamping member, respectively an internal part fixed directly on the front end of the electrode-carrying arm and constituting the fixed jaw of the clamp and an external part connected rigidly to the internal part by at least one lateral arm of fixed length, the movable jaw being slidably mounted horizontally in said support body and the clamping member being interposed between the movable jaw and the external support part and bearing on the latter for determining the tightening of the electrode against the fixed jaw, the latter carrying at least one conductive part constituting the electrical contact part.

Advantageously, the fixed jaw has the shape of a
U wide open comprising a central fixing part on the end of the electrode holder arm and two lateral wings each carrying an electrode support pad, said pads being made of conductive material and constituting the contact parts of the electrode connected to the current source.

 Preferably, the two conductive support pads are connected to each other by a U-shaped conductive part fixed to the fixed jaw with interposition of insulation and to which the first supply conductor is connected.

 Furthermore, in a preferred embodiment, the clamping member of the clamp comprises a stack of elastic washers associated with at least one hydraulic or pneumatic cylinder for controlling the tightening of the stack, the latter being supported on one side. on the external support part and on the other on the movable jaw and having, in the fully relaxed state, a length such that the movable jaw is at a distance from the fixed jaw less than the thickness of an electrode.

 The cylinder for controlling the tightening of the stack advantageously comprises a cylinder body fixed on the external support part and inside which slides a piston associated with a rod connected at its other end to the movable jaw and on which are threaded stacked washers.

 In a first advantageous embodiment, the first electrode supply conductor extends along the electrode-carrying arm, outside of the latter.

 In another embodiment, the first conductor is constituted by the electrode-carrying arm itself, the latter comprising an outer envelope of conductive material pressed against an internal part of the support of resistant material.

 However, the electrode holder arm itself constituting the first conductor can also be made of a material that is both conductive and sufficiently resistant to support the electrode, for example aluminum.

 However, in a particularly advantageous embodiment, the first conductor extends inside the arm which is constituted by a hollow profile carrying at its front end at least one pad of conductive material constituting at least part of the fixed jaw and to which the end of the first conductor is connected.

 Furthermore, the electrode-carrying arm can be limited by an external wall associated with a parallel internal wall so as to constitute a double envelope limiting an external annular space allowing the circulation of a cooling fluid and an internal central space in which is advantageously placed the supply conductor.

 The invention will be better understood from the following description of certain preferred embodiments, given by way of example and shown in the accompanying drawings.

 Figures la and lb show schematically two usual embodiments of an electrode holding device.

 Figure 2 schematically shows a holding device according to the invention.

 Figures 3 and 4 schematically show two other embodiments of the invention.

 Figure 5 shows in elevation an electrode holder arm provided with a holding device according to the invention.

 Figure 6 is a top view partially in section.

 Figure 7 is a detail view, in section through a horizontal plane of the electrode holding device.

 Figure 8 shows in elevation another embodiment of the electrode holder arm.

 In Figure la, there is shown schematically an electrode-carrying arm 1 extending in overhang from a support mat M above an electric oven closed by a cover C in which is formed at least one orifice allowing the penetration of an electrode E carried at the free end of the arm 1 by means of a holding device 2.

 In this known embodiment, the holding device consists of a hollow cylindrical body 21 fixed to the front end of the arm 1 which limits a orifice for the passage of the electrode E. The latter is pressed against the front face of the cylindrical body 2 by a shoe 22 pushed back by a clamping device 23 of the spring or other type.

 It is seen that in such an embodiment the body 21 which surrounds the electrode E can have a fairly reduced thickness just sufficient to give the necessary resistance and that the clamping device 23 actuating the movable jaw 22 can be placed inside. of the arm 1. Normally the electrical contact is ensured by the body 21 which can be made of conductive material and connected to the current source.

 FIG. 1b shows another known arrangement in which the movable jaw 22 'is placed on the other side of the electrode E with respect to the arm 1 and constitutes the base of a stirrup 24 surrounding the electrode and which is pulled inward by a clamping device 23 to press the electrode E onto the fixed jaw 26 placed at the end of the arm 1.

 It can be seen that, in both cases, the clamping device is placed inside the electrode-carrying arm, and that only a support shoe or shoe, of relatively reduced thickness, is placed beyond the 'electrode. Thus, the size of the clamp is reduced, which is particularly advantageous in alternating current ovens, several electrodes are used which are relatively close to one another.

 As these provisions were satisfactory in ensuring the maintenance and the sliding guide of the electrode, they have been used commonly up to now.

 Contrary to acquired habits, the applicant company however had the idea of modifying the electrode holding device so as to be able to simplify it, facilitate its maintenance and ensure under better conditions the electrical supply of the electrode.

 The principle of the invention is shown diagrammatically, in three exemplary embodiments, in FIGS. 2, 3 and 4.

 We see that, the clamp comprising, as usual, a fixed jaw, a movable jaw and a clamping device, only the fixed jaw 31 is placed on the side of the support mAt M, at the front end 11 of the electrode holder arm 1 and that the clamping device 5 associated with the movable jaw 32 is placed on the other side of the electrode, in a support body consisting of a rigid part 4 in the form of a ring and comprising a support plate external 41 rigidly connected to the front end 11 of the electrode-carrying arm 1 by two lateral arms 42 passing on either side of the electrode E and thus limiting, in front of the latter, a hollow space 40 in which can be placed the movable jaw 32 and the clamping device 5 which bears on the plate 41 to effect the clamping of the electrode by bringing the movable jaw 32 towards the fixed jaw 31. The latter can carry contact parts in copper or else made itself -theme made of copper to constitute the electrical contact part to which a first supply conductor 6 is connected which extends along the electrode-carrying arm 1 as far as the rear end 12 thereof and is extended by at least one second conductor 63 connected to the current source 60.

 It appears that, in such an arrangement, the whole of the movable jaw and of the clamping device is perfectly accessible since it is placed outside the electrode-carrying arm 1, while remaining protected by the support body. 4. Furthermore, the constitution of the electrode-carrying arm, and in particular of its front end 11 is simplified since the latter only carries the fixed machine 31 also constituting the electrical contact part. Thus, one can intervene on the clamping device of the clamp and, in particular, access the clamping cylinder, without dismantling the clamp and, in particular, all the electrical supply members remain fixed on the arm.

 Admittedly, the size of the electrode-carrying arm 1 is increased since the support body 4 extends beyond the electrode E. But, in many cases, this does not present any drawbacks, in particular for ovens supplied with direct current, in which the electrodes can between relatively spaced and which, moreover, often have only one or two electrodes.

 In FIG. 3, an even simpler arrangement is shown, in which the electrode-carrying arm 1, which can be made of aluminum or copper-plated steel, itself constitutes the current-supplying member, the second conductor 63 being connected directly to the rear end 12 of the arm which leads the current through its external wall to the fixed jaw 31 which is fixed directly to the front end 11 and of which at least one contact part is made up of conductive material, for example copper.

In the more perfected embodiment shown in FIG. 4, the first current supply conductor consists of a rod 6, preferably rigid, extending inside the electrode holder arm 1 and over all the length thereof and the rear end of which is connected to the power source 60 by the second flexible conductor 63 while its front end is connected to a fixed part 62 of conductive material constituting at least part of the fixed jaw 31 to which the electrode E is applied by the movable jaw 32 of the clamp
The conductive rod 6 is held inside the arm 1 by support members 16, preferably by means of insulators, but this is not essential, the arm 1 possibly being able to be brought to the potential of the electrode if necessary precautions are taken.

 This preferred embodiment of the electrode-carrying arm is shown in more detail in FIGS. 5 to 8.

 Figure 5 is a side view! in elevation, of the electrode-carrying arm 1 carried by a support mat M of which only the upper part has been shown. and provided, at its front end 11, with a clamp 3 for holding the electrode E placed in a support body 4 which extends in the extension of the arm 1 beyond the electrode E.

 The support body 4 which is shown in horizontal section in Figure 6 and, in more detail, in Figure 7, consists of a hollow monobloc piece! comprising two support parts, respectively an external part 41 and an internal part 43 spaced from one another and rigidly connected together by two lateral arms 42.

The latter are further connected by an intermediate plate 45 which thus limits, on the side of the internal part 43, an orifice 44 for passage of the electrode (E) and, on the side of the external part 41 a hollow space 40 in which the clamping device 5 can be placed.

 The internal support part 43 consists of a rigid plate forming a flange which can be applied and fixed to the front end 11 of the arm 1.

 The whole of the support body 4 is symmetrical with respect to an axis Y ′ Y which, when the body 4 is fixed to the arm 1, is located in the extension of the longitudinal axis X ′ X of the arm.

 Advantageously, the fixing flange 43 is associated with a curved U-shaped plate 46 comprising a central part 46a perpendicular to the axis Y 'Y, extended by two lateral wings 46b inclined symmetrically with respect to the axis Y' Y and which is supported on the flange 43 by means of a spacer tube 43a. The flange 43 and the curved plate 46 thus forming a rigid assembly constituting the fixed jaw 31 of the holding clamp 3.

 The movable jaw of the plate 3 is constituted by a piece 32 in the form of a shoe which can slide along the axis of the axis Y ′ Y and is actuated, for this purpose, by the clamping device 5 so as to apply the electrode E on the fixed jaw 31.

 The clamping device 5 comprises, a stack of elastic washers 51, threaded on a rod 52 which extends along the axis Y 'Y between a rear end 52a on which is fixed the shoe 32 and a front end 52b fixed on the piston 53 of a jack whose body 54 is fixed on the external support part 41 of the body 4. This consists of a plate provided with a central orifice in which the body 54 of the jack is threaded, this the latter being integral with a flange 54 'which is applied and removably fixed to the plate 41.

 The stack of elastic washers 51 is maintained between the internal face 54a of the body of the jack and a washer 55 which bears on a shoulder 56 of the rod 52.

Furthermore, to maintain the rod 52 along the axis
Y 'Y, the washer 55 is slidably mounted in a fixed ring 56 connected by a cylindrical wall 57 to the internal face 54a of the body 54 of the jack.

 Under the action of the elastic washers 51, the shoe 32 constituting the movable jaw pushes the electrode 1 against two support pads 64 of conductive material fixed on two wings of a connecting piece 65 of conductive material having a U shape corresponding to that of the fixed jaw 31 so as to bear on it via an insulator 66.

 The assembly is fixed by bolts 68 themselves insulated with respect to the metal parts of the jaw 31.

 Preferably, the shoe 32 and the support pads 64 have curved faces of curvature corresponding to the profile, generally circular, of the electrode.

 It may, moreover, be advantageous to fix each shoe 64 on the fixed jaw 31 by means of an articulation giving said shoe a certain latitude of orientation to better adapt to the profile of the electrode (E). .

 The clamping device 5 thus forms a compact assembly which can be housed in the space 40 limited by the intermediate plate 45, the two lateral arms 42 and the external flange 41. This assembly is always accessible and can easily be dismantled and replaced without other disassembly than that of the flange 54 '.

The stroke of the jack 54 is determined so that, when the piston 53 bears, at the end of the stroke, on the rear face 54a of the jack body, the distance between the movable shoe 32 and the bearing pads 64 of the fixed jaw 31 is less than that which corresponds to the minimum diameter of the electrode (E). In this way, the elastic stack 51 always tends to strongly apply the electrode E against the pads 61 to maintain the electrode and to ensure electrical contact.
The jack 54 can be single acting, and of the hydraulic or pneumatic type, the chamber 50 between the internal face 54a and the piston 53 being able to be supplied with fluid by a pipe 71 connected to a source of pressurized fluid by a circuit d 7.

 The clamping device 5, thus placed in the space 40, between the two arms 42, 42 'is perfectly protected, for example against impact, inside the support body 4.

But, according to another advantageous characteristic of the invention, the support body 4 also provides thermal protection of the clamp 3 and of its clamping device 5 against heat radiation and steel projections possibly coming from the metal bath which is located directly below the clamp 3
Indeed, the support body 4, which is made in mechanical welded construction in the form of a hollow annular box, each lateral arm 42 consisting of two spaced faces, an external lateral face 47 which extends between the plate outer 41 and the inner plate 45 and an inner face 48 which comprises a plate 48a extending between the outer plate 41 and the intermediate plate 45 and a second table 48b which extends between the intermediate plate 45 and the side edges 46b of the curved plate 46. The two tabs 48b which laterally limit the orifice 44 are themselves curved so as to allow the passage of the electrode E.

 The assembly is covered by two plates 49 constituting the upper and lower faces of the box 4 and welded to the upper and lower edges of the external lateral faces 47, of the plates 41, 45 and 43 and of the rear parts 48b of the internal faces 48.

 The rear part of the plates 49 is open to the right of the pantry 44 to allow the passage of the electrode E, the front part covering the clamping device 5.

 At this level, the upper and lower edges of the front parts 48a of the internal faces 48 are connected by internal plates 49 ′ slightly spaced from the external plates 49, so as to provide, in front of the electrode (E), two spaces communication between the two hollow sides 42, 42 'of the box 4 which, on the other hand, are separated from each other, in the rear part 31, by a partition 43b.

 It is thus possible to circulate a cooling fluid inside the box.

 In a particularly advantageous manner, the cooling circuit is placed inside the arm 1 so as to be well protected.

 To this end, as shown in FIGS. 5 and 7, the arm is advantageously limited by a rigid external lateral wall 10 associated with an internal wall 10 ′ so as to constitute a double envelope limiting an external annular space 13 and a central space 13 ′ in which the electrical conductor 6 is placed.

 The latter is preferably made of a copper tube or other conductive material whose front end 61 is provided with a flange that passes inside the tube 43 to be fixed on the central part of the conductive part 65. The tube 6 opens at the inlet of a cooling circuit 67 formed inside the conductive part 65 and opens at its other end inside the side 42 of the box 4 passing through a through hole 46c the curved plate 46.

 To simplify the figure, circuit 67 has been simply shown in dashed lines.

 A cooling fluid such as water, supplied by the tubular conductor 6 thus passes first into the conductive part 65 by the circuit 67, then circulates successively in the cste 42 then in the side 42 'of the box 4, up to the rear part 31 communicating through orifices 15 with the annular space 13 through which the fluid is discharged.

 This effectively ensures cooling of the box 4 and the support arm 1, as well as of all the conductive parts.

 Furthermore, all the other members can between placed inside the arm 1 and the box 4, sheltered from shocks and thermal radiation.

 This is the case, not only of the conductor 6 but also of the hydraulic circuits 7 of the jack 54 which can be passed inside one of the arms 42 ′ of the box 4 and into the annular space 13, sheltered from all attacks.

 The rear end 62 of the tube 6 is fixed to the rear end 12 of the arm 1 by an insulating support 16 ′ and is provided with one or more lugs i7 for connecting the flexible conductor (s) 63.

 Of course, the invention is not limited to the details of the preferred embodiment which has just been described, other equivalent provisions which can be used while remaining within the scope of the claims.

 Thus, in the embodiment of Figure 8, the conductor 6, which may consist of two parallel conductors, is placed outside the arm 1 and carried by supports 15, a rear support 15 'being provided with a part 17 to which the rear end 62 of the conductor 6 can be fixed as well as connection terminals for the conductors 63.

AT
But other variants could be envisaged, in particular for the production of the clamp 3 of the clamping device 5, or of the support body 4, the latter being able, for example, to comprise a single lateral arm for maintaining the part d support 41 at a fixed distance from m-jaw 31.

Claims (17)

 1. An electrode holding device, especially for an electric arc furnace, comprising an electrode-carrying arm (1) extending in overhang, substantially horizontally between a rear end (12) provided with means for attachment to a support mast (M) and a front end (11) provided with means for supporting and supplying the electrode (E) comprising an electrode holding clamp (3) comprising two jaws, respectively fixed ( 31) and mobile (32), associated with a member (5) for clamping an electrode (E) interposed between said jib and is means (6) for electrical supply of the electrode, comprising at least one contact piece (61) applied to the electrode (E) and connected to a current source (60) by at least one first conductor (6) extending along the electrode-carrying arm (5) up to m * t support (M) and extended by at least one second conductor (63) extending from the support mast (M) usqutà la current source (60), characterized in that the electrode-carrying arm (1) is extended beyond the electrode (E) by a rigid hollow piece (4) forming a support body for the clamp and comprising two support parts (41, 43) spaced from each other by a distance greater than the thickness of the electrode (E) increased by the size of the clamping member (5), respectively an internal part (43) fixed directly on the front end (of the electrode-carrying arm (1) and constituting at least part of the fixed jaw (31) of the clamp and an external part (41) rigidly connected to the part internal (43) by at least one lateral arm (42) of fixed length, the movable jaw (32) being slidably mounted horizontally in said support body (4) and the clamping member (5) being interposed between the movable jaw (32) and the external support part (41) and bearing thereon to determine the tightening of the electrode (E) against the fixed jaw (31), the latter carrying at least one conductive part (64) constituting the electrical contact part.  2. Holding device according to claim I, A characterized in that the fixed jaw (31) has the shape of a widely open U comprising a central part (43, 46) for fixing on the end (11) of the electrode holder arm and two lateral wings (46b) each carrying an electrode support pad (E), said pads (64) being made of conductive material and constituting the contact parts of the electrode (E), connected to the current source (60).  3. Holding device according to claim 2, characterized in that each support pad (64) is hingedly mounted on the fixed mSchoire (31) so as to adapt to the profile of the electrode.  4. Holding device according to one of claims 2 and 3, characterized in that the two conductive support pads (64) are interconnected by a conductive piece (65) U-shaped fixed on the fixed jaw (31) with the interposition of an insulator (66) and to which the first supply conductor (6) is connected.  5. Holding device according to one of the preceding claims, characterized in that the clamping member (5) of the clamp (3) comprises a stack of elastic washers (51) associated with at least one jack (54) hydraulic or pneumatic control of the tightening of the stack (51), the latter bearing on one side on the external support part (41) and on the other on the movable jaw (32) and having at the being completely relaxed, such a length on the movable jaw (32) is at a distance from the fixed jaw (31) less than the thickness of an electrode (E).  6. Holding device according to claim 5, characterized in that the cylinder for controlling the tightening of the stack (51) comprises a cylinder body (54) fixed to the external support part (41) and to the inside of which slides a piston (53) associated with a  A rod (52) connected at its other end to the movable jaw f32) and on which is threaded the stack of washers (51).  7. Holding device according to one of the preceding claims, characterized in that the first conductor (6) extends along the length of the electrode holder arm (1), outside of the latter.  8. Holding device according to one of claims? to 6, characterized in that the first conductor (6) is constituted by the electrode-carrying arm (1) itself, the latter comprising an outer casing (14) of conductive material pressed against an internal support part in resistant material.  9. Holding device according to one of claims 1 to 6, characterized in that the first conductor (6) is constituted by the electrode holder arm (1) itself, the latter being made of a material such that aluminum that is both conductive and strong enough to support the electrode.  10. Holding device according to one of claims 1 to 6, characterized in that the electrode-carrying arm (1) consists of a hollow profile (1Q) and that the first conductor (6) extends to the inside the arm t to the front end (11) of the latter and is connected to the care a piece (65) of conductive material constituting at least part of the fixed jaw (31)  Holding device according to one of the preceding claims, characterized in that the support body (4) comprises two parallel lateral arms (42, 42 ') extending between two spaced apart plates (41, 43) constituting, respectively, the external support part (41) and the internal support part (43), the latter being fixed on the end (11) of the arm (1).  12. Holding device according to claim 11, characterized in that the two lateral arms (42, 42 ') are connected by an intermediate plate (45) limiting, on the csté of the internal support part (43) an orifice (44) for the passage of the electrode E and, from the side of the external support part (41), a space (40) in which the clamping device (5) can be coated.  13. Holding device according to one of the preceding claims, characterized in that the fixed jaw (31) consists of two separated parts, respectively a part (43) for fixing on the end (11) of the arm (1 ) and a piece (46) for supporting the electrode E connected to the plate (43) by a spacer piece (43a).  14. Holding device according to one of the preceding claims, characterized in that the support body (4) has the shape of a hollow rigid box limiting an annular space comprising, on either side of the orifice (44) for passage of the electrode (E), two lateral sides (42, 42 ′) which are isolated from each other, on the side of the fixed jaw (31), by a partition wall (43b ) and which communicate with each other in the front part of the box (4), on the other side of the electrode (E), the box (4) being associated with circuits for supplying and discharging a fluid coolant opening respectively in the two sides (42, 42 '), on either side of the partition (43b).  15. Holding device according to claim 14, characterized in that each arm (42, 42 ') consists of two spaced apart faces, respectively an outer face (47) extending between the outer support part (41) and the fixing part (43), and an internal face (48) comprising a first part (48a) extending between the external bearing part (41) and the intermediate part (45), and a second part (48 ') extending between the intermediate part (45) and the support plate (46) of the jaw (31).  16. Holding device according to claim 15, characterized in that the edges, respectively upper and lower of the external lateral faces (47) of the two arms (42, 42 ') are connected by plates (49) constituting the two faces , respectively upper and lower of the box (4), the latter comprising a rear part (49a) provided with an opening for passage of the electrode and a front part (49b) covering the clamping device (5), and that the upper and lower edges of the sheets constituting the first parts (48a) of the internal faces (48) of the two arms (42, 42 ') are connected by two internal plates (49') slightly spaced from the external plates (49), respectively, upper and lower, of the box (4) to provide communication spaces between the two cstés (42, 42 ') of the box (4).  17. Holding device according to one of the preceding claims, characterized in that the electrode-carrying arm (1) is limited by an external wall (10) associated with an internal wall (10 ') parallel so as to constitute a double envelope limiting an external annular space (13) and an internal central space (13 ').  18. Holding device according to one of claims 14 to 16, characterized in that the electrode holder arm (1) forms a double envelope limiting an external annular space (13) and a central space (13 ') and that the supply conductor (6) consists of a tube applied to a conductive part (65) of the fixed jaw (31) and emerging at the inlet of a pipe (67) formed inside the part conductive (65) and opening at its other end inside one of the sides (42) of the hollow annular box (4), the other side of which (42 ') communicates with the annular space (13) for allow the circulation of a heat transfer fluid successively in the conductor (5), the conductive part (65), the box (4), and the annular space (13).