EP2082069B1 - Method and installation for introducing a cored wire into a bath of molten metal - Google Patents

Description

The present invention relates to the field of metallurgy, more particularly the adjustment of the composition or the inclusion treatment of a bath of molten metal by the introduction of an additive using a cored wire containing said additive.

More specifically, it relates to a method and an installation for introducing a flux-cored wire into an improved effective additive adducting metal melt bath.

Metals and metal alloys such as steel or cast iron, have properties that depend in particular on their composition. In the manufacture of metals and metal alloys, one generally starts from a base composition whose content in certain components is adjusted according to the desired final composition.

This adjustment is done according to several techniques among which the introduction into the bath of molten metal of a predetermined length of a cored wire, that is to say a longiform element consisting of an outer envelope in which is contained in powder form, the additive which is desired introduction.

The envelope of the cored wire is generally made from a metal sheet of small thickness or strip, whose two opposite longitudinal edges are folded so as to hook to each other after having given said sheet a tubular configuration. By this mechanical stapling of the two edges, a good seal is obtained vis-à-vis the additive.

This cored wire is produced in the form of a coil of great length, for example 6000 meters. Classically, as illustrated schematically in figure 1 of the document FR 2.871.477 , it is extracted from the coil which is either static, arranged inside a cage, or dynamic, wound on a drum, then it passes in a horizontal course in an injector, which drives it into a guide tube elbow. The cored wire exits the distal end of the guide tube at a determined height above the surface bath, of the order of 1 to 1.4 meters. The injector shown in figure 1 of the document FR 2.871.477 is a conventional injector comprising three sets of two cylindrical rollers, driven in rotation, between which passes the cored wire. The pressure exerted by rollers must be sufficient to allow extraction of the wire from the coil and driving said wire to the bath, through the guide tube. This pressure generally causes deformation of the wire in cross section.

It is known that the implementation of the technique of adjusting the composition of a molten metal bath with a cored wire can cause difficulties with certain additives, in particular calcium, magnesium, selenium and sulfur. For some, the heat of the molten metal bath causes the cored wire to explode in an area very close to the surface of the bath. For others, the additive vaporizes very quickly and close to the surface. In all cases, there is a strong surface reactivity generating a certain number of phenomena: oxidation and / or nitriding of the bath, projection of the liquid metal, strong fumes emanation.

With this type of additive, it is found that to obtain the adjustment of the bath composition in the additive in question, it takes a length of cored wire and therefore a quantity of additives actually provided by the wire which is much more important than the theoretical length that would have been necessary if all the additive contributed had participated in the adjustment of the composition of the bath.

This introduction operation therefore generally has a very low yield, addition yield which can be of the order of 10 to 15%.

It has already been sought to improve the addition efficiency, by introducing the cored wire into the bath by passing it inside a tube or protective lance, refractory material, previously introduced into the bath. However, the presence of this tube or refractory lance which plunges into the bath has in addition to its high cost, other disadvantages related in particular to the risk of clogging of the tube or lance and pollution of the bath following the erosion of the tube or the spear by the bath itself.

It has also been proposed, in order to improve the addition efficiency, to cover the metal casing in which the additive is located by a second casing which is combustible but without leaving troublesome residues and which momentarily delays the propagation of heat towards the heart of the cored wire. This is in particular one or more paper strips wound helically around the first metal shell. This paper is chosen to have an ignition resistance and a coefficient of thermal resistance higher than those of a plain paper sheet.

The presence of this second envelope makes it possible to introduce the cored wire to a greater depth and thus to minimize the effects of explosion and / or vaporization of the additive.

To prevent this second envelope can be degraded during the reel and especially when removing the coil, it is preferable to provide a third metal casing of the same type as the first envelope.

This improvement brought to the cored wire, described in the document FR 2.871.477 has already made it possible to make a significant improvement in the efficiency of the operation of introduction of the cored wire, particularly with regard to additives such as calcium, magnesium, selenium and sulfur. The document JPS59-162161 U discloses a drive installation of a cored wire. This installation comprises two pairs of rollers for driving the cored wire, these pairs each comprise a drive roller and a driven roller, pressed against the drive roller. For each of these pairs, one roll comprises a flat wafer and the other comprises a concave wafer, wrapping the wire partially. It is specified that the wire is flattened as to the contact with the flat wafer in order to improve the linearity of the cored wire.

The purpose of the applicant is to propose a complementary improvement which is not related to a change in the structure of the cored wire but which takes into account the method and the installation of introduction.

This is a method which, in known manner, consists of extracting the cored wire from a coil and driving it in displacement to the metal bath, part of the path of the cored wire being made in a tube of guidance whose distal end is at a predetermined height of the surface of the metal bath.

Typically, according to the present invention, the cored wire is driven and is subjected to a straightening operation, under conditions not substantially altering its substantially circular section and allowing its introduction and penetration into the depth of the bath according to a vertical direction.

It is indeed the merit of the applicant to have been able to note the impact on the performance of the introduction of the flux-cored operation, on the one hand, of the deformation of the cross section of the wire caused by the systems. current plant drive and secondly the natural tendency of the wire, when entering the bath, to find the curved configuration he had in the coil. These two aspects both have the practical consequence that the cored wire, when it enters the molten metal bath, has a direction not rectilinear but curving towards the surface of the bath, which limits the depth of the bath. introduction into the bath. This is added to the fact that in the current wire injection installations the direction of introduction of the cored wire, in particular that of the guide tube, is oblique with respect to the surface of the bath, which only aggravates the phenomenon of rising of the wire towards the surface of the bath.

Thus according to the concept of the present invention, it is to implement the conditions that allow the cored wire penetrates deep into the bath in a direction that remains as vertical as possible over its entire height before disintegration.

The straightening operation is carried out by the passage of the cored wire, before entering the guide tube, in several sets of two pressure rollers. The pressure exerted, the number of sets of the pressure rollers, their respective distance, the configuration of the contact with the flux-cored wire are determined so as to obtain the desired straightening, namely that in the free state the flux-cored wire retains a rectilinear configuration and does not tend to resume the curved configuration that it had when stored in the coil, and so that the straightened cored wire keeps its substantially circular section.

During this operation, it is indeed a question of applying to the surface of the wire equally distributed and sufficient efforts to overcome and cancel the effect of the internal stresses that have been induced during the winding and unwinding operations.

In an alternative embodiment, the contact faces of the rollers with the cored wire are concave.

Preferably, in this case, the radius of curvature of the concave faces of the pressure rollers is substantially the same as that of the cored wire. Thus the pressure exerted by the rollers is exerted substantially radially on the cored wire so that there is no crippling crushing or deforming said wire, even with significant pressure. This makes it possible to limit the number of sets of pressure rollers, for example from two to five sets of two rollers.

It is understood that optimally, the curvature of the concave faces of the pressure rollers should be strictly the same as that of the cored wire, which would make it possible to have a total homogeneity of the pressure forces exerted radially on said wire over the entire surface of the contact between the wire and the roll, but would require to change the rollers according to the diameter of the wire. Nevertheless, it has been found that the radius of curvature of the concave faces may be slightly different from that of the cored wire without causing crushing or annoying deformation of the wire while preserving the correct straightening of the wire.

This is not exclusive, however. Satisfactory straightening, without any unacceptable deformation of the section of the cored wire, was obtained by implementing a larger number of sets of pressure rollers, for example about fifteen games, with a more limited pressure per set. In this case , the contact faces are formed by the two oblique walls of a peripheral groove of triangular section. The pressure exerted by each roller is applied to the cored wire along two continuous lines of contact, and not according to a contact surface as in the previous variant. However, because of the lower pressure exerted by each game and the greater number of games, there is no disturbing deformation of the circular section of the cored wire.

According to an alternative embodiment, the cored wire is held laterally during its passage between sets of pressure rollers, in particular by intermediate guide tubes. The purpose of this particular provision is to keep the cored wire so that it remains straight during its course in the set of sets of two pressure rollers.

In an alternative embodiment, the driving of the cored wire is carried out at the same time as its straightening, in particular when the straightening is obtained by passing between successive sets of rollers, some of these rollers being then rotated.

This is not exclusive, the drive of the cored wire can in particular be performed upstream and regardless of its recovery. In this case, the straightening operation is performed under conditions to rectify the cross-section deformation of the wire caused by the drive system. This is preferably obtained with a rectification using rollers having concave faces whose radius of curvature is substantially the same as that of the undeformed cored wire.

It is another object of the invention to provide an installation for introducing a cored wire into a bath of molten metal which comprises means for driving said cored wire from a coil and a guide tube of the cored wire. whose distal end is at a determined height H of the bath surface.

Typically, according to the present invention, the guide tube has a vertical direction. In addition, the installation comprises means for straightening the cored wire which are arranged before entering the guide tube and able to give the cored wire vertical rectilinear direction without substantially altering its substantially circular section.

According to the invention, the rectifying means consist of a plurality of sets of two pressure rollers, the contact of each roller with the cored wire being made according to a contact surface or in two continuous contact lines.

In the first variant embodiment, the rectifying means consist of a limited number, for example from three to five, sets of pressure rollers whose contact faces with the cored wire are concave; of preferably the concave contact face of each pressure roll has a radius of curvature which is substantially the same as that of the cored wire.

Advantageously, in this case, each contact face of each roll corresponds to an angular portion of between 120 and 180 °. It is understood that in theory the angular portion of 180 ° provides a radial distribution of pressure forces over the entire outer periphery of a reference wire whose radius corresponds strictly to the radius of curvature of the pressure rollers. The angular portion in the range between 120 ° and 180 °, however, straighten wires of diameter greater than this reference wire without crushing or annoying deformation.

In the second embodiment, the straightening means are constituted by a large number, for example from twelve to twenty, sets of pressure rollers, in which each roll has a peripheral groove of triangular section, delimiting two oblique contact faces. with the cored wire.

Preferably, the installation comprises, between each pair of sets of pressure rollers, an intermediate guide tube capable of holding the wire laterally as it moves between sets of pressure rollers in a rectilinear direction.

According to an alternative embodiment, the ratio between the inner diameter of the guide tube, and possibly interposed tubes, and the diameter of the cored wire is of the order of 1.5 to 5. The guide tube must allow free movement of the cored wire by forcing it nevertheless to maintain a rectilinear vertical direction. This function is fulfilled for the aforementioned range by the same guide tube for the usual range of flux cored wire diameter.

According to an alternative embodiment, the distal end of the guide tube is provided with a protective tip more thermally resistant than said guide tube. The purpose of the implementation of this protective tip is to avoid alteration of the distal end of the guide tube due to the heat of the molten metal bath and also due to projections.

The protective tip may extend beyond the distal end of the guide tube over a given distance, for example of the order of 10 to 30 cm.

Preferably, the guide tube is in at least two parts, namely on the one hand, a proximal part and on the other hand, a distal portion equipped with the protective cap, the two said parts being securable by means removable connection, in particular by threading or bayonet system, so as to allow the replacement of the distal portion of the tube and the protective tip.

In an alternative embodiment, the straightening means of the cored wire act as drive means.

According to an embodiment of the variant, wherein the rectifying means consist of a limited number of sets of two pressure rollers, each set comprises a driven roller and a free roller. In addition, the free roller is mounted on a pivoting arm, forming a rocker, movable cylinder.

In another variant embodiment, the rectifying means are dissociated from the drive means, the latter consisting of an injector disposed upstream of the rectifying means. In this case, the cored wire necessarily has in the rectifying means, a vertical direction. In addition, it is appropriate that the rectifying means are able to correct the deformation caused on the wire, in cross section, by the rectifying means.

• la figure 1 est une représentation schématique de ladite installation, incluant le parcours du fil fourré ;
• la figure 2 est une représentation schématique en coupe d'un ensemble redresseur composé d'une succession de jeux de deux rouleaux de pression ;
• la figure 3 est une représentation schématique et partielle en coupe de deux rouleaux de pression agissant sur le fil fourré ;
• la figure 4 est une représentation schématique en coupe de la portion distale du tube de guidage avec son embout de protection.

The present invention will be better understood on reading the description which will be made of the introduction of a flux-cored wire into a bath of molten metal through the implementation of an installation of which the preferred embodiment is illustrated. by the appended drawing in which:

• the figure 1 is a schematic representation of said installation, including the course of the cored wire;
• the figure 2 is a schematic sectional representation of a rectifier assembly composed of a succession of sets of two pressure rollers;
• the figure 3 is a schematic and partial sectional representation of two pressure rollers acting on the cored wire;
• the figure 4 is a schematic representation in section of the distal portion of the guide tube with its protective tip.

The installation 1 is intended for the introduction of a cored wire 2 into a bath 3 of molten metal in order to adjust the composition of this bath or to treat it with a component or additive, which is contained under powder form inside the cored wire 2.

In the example shown in figure 3 , the cored wire 2 has a structure which is in accordance with that described in the document FR 2.871.477 . More specifically, the additive 4, in powder form, is housed inside a first metal sheath 5, which is surrounded by a casing 6 which, itself, is surrounded by a second metal sheath 7 In cross section as shown on the figure 3 , the cored wire 2 has a generally circular configuration, the intermediate casing 6 being sandwiched between the two metal sheaths 5 and 7. Each of the two metal sheaths 5, 7 is made from a strip whose two longitudinal edges opposed are folded so as to hook to each other after the strip has been given a substantially tubular configuration. These attachment zones are schematically represented on the figure 3 under the references 5a and 7a, being turned towards the inside of the tubular wire 2.

The intermediate casing 6 is made of a material which is combustible but without leaving troublesome residues in the molten metal bath and which momentarily delays the propagation of heat towards the core of the cored wire 2. In a specific embodiment, this interlayer consists of several strips of paper wound helically around the first metal sheath 5, being a pyrotechnic type paper, having a higher fire resistance and thermal resistance coefficient to those of ordinary paper. Although the above-described structure of the cored wire 2 is preferred, it is not, however, exclusive of the present invention.

The supply of cored wire 2 is made from a platform 8 supporting two coils 9, 9 'in which large and continuous lengths of cored wire 2 are wound, for example of the order of 6000 linear meters. The second coil 9 'serves as a reserve for the supply of wire at the end of the first coil 9.

In the illustrated embodiment, each coil 9 is held statically inside a cage 10. During the extraction of the cored wire, the coil 9 remains fixed, the cored wire 2 being extracted from the heart of the reel. This mode of presentation of the cored wire 2 has the advantage over a conventional winding on a drum does not require rotation of the coil during unwinding. On the other hand, it has the major disadvantage that can be overcome by the present invention, namely to considerably increase the deformation capacity of the flux-cored wire in the free state, which deformation prevents the rectilinear penetration of said wire into the molten metal bath. .

The installation 1 comprises successively on the path of the cored wire 2 a guide assembly 11, a trainer and rectifier assembly 12, a guide tube 13 and a protective cap 14. The guide assembly 11 serves to accompany the cored wire 2 taken from the coil 9 during its transfer to the input of the trainer / rectifier assembly 12. This guide assembly 11 comprises a number of rollers 15 which are rotatably mounted each along an axis These rollers 15 are mounted on a frame 16 having generally an inverted U shape, with two elbows whose ends respectively upstream 16a and downstream 16b have a substantially vertical direction. The cored wire 2 taken from the coil 9 is introduced into the upstream end 11a of the guide assembly 11, it is supported by the rollers 15 and prevented from coming out of the guide assembly 11 because of its configuration. cage form, with hoops 17 fixed to the frame 16 at the level and / or between the rollers 15.

As it passes through the guide assembly 11, the cored wire is first displaced from bottom to top and then substantially horizontally and finally from top to bottom, having a substantially vertical direction when it is introduced into the trainer / rectifier assembly. 12 at the outlet of the downstream end 11b of said assembly 11.

In the coil 9, the cored wire 2 is wound in the form of substantially joined turns. During the extraction of the wire 2 from the core of the coil 9, the wire drawn upward gradually deforms to move from the spiral configuration to a substantially rectilinear configuration due to the traction exerted. Nevertheless, this passage generates internal stresses that cause the wire to keep "in memory" its configuration in the initial turn, a configuration that it finds at least in part when the traction exerted on it ceases. These internal stresses are in addition to those that had been caused during the winding operation.

It is the function imparted to the rectifier assembly that overcoming and canceling the effect of all these internal stresses prevents the flux-cored wire, once introduced into the bath 3, from continuing to penetrate in a rectilinear manner.

In the embodiment which will now be described, the assembly 12 fulfills both the driving function of the cored wire 2 and the straightening function of said wire. This is not exclusive, however, the drive function can be dissociated from the recovery function; in this case, however, it is preferable that the drive assembly is disposed upstream of the recovery assembly and that the path of the wire in the recovery assembly is in a vertical direction relative to the theoretical plane PP 'of the surface of the bath of molten metal 3.

The trainer / rectifier assembly 12 which is illustrated in FIG. figure 2 comprises a succession of five sets 18 of two pressure rollers 19,20 between which passes the cored wire 2, in a vertical direction. Each roller 19,20 of each set 18 is in contact with the cored wire 2 according to a contact face 21,22 which is concave. In the example shown in figure 3 , each concave face 21,22 has approximately the same radius of curvature as that of the outer face of the cored wire 2, namely the second metal sheath 7. As explained above, these rollers 19,20 could nevertheless be used for training and straightening wire 2 having a radius of curvature less than that of the wire shown.

However, it is preferable for each concave face 21, 22 to correspond to an angular portion α of between 120 ° and 180 °, for example 130 °, in particular when the driving and straightening operations are independent and the straightening means must be correct the deformation caused on the wire during its passage in the drive means.

One of the rollers 19 is rotated, while the other 20 is freely mounted on its axis. This free roller 20 is mounted on a pivoting arm 23 whose pivot axis 28 is offset relative to said free roller 20. This pivoting arm 23 is moved by a jack 24 whose body 25 is pivotally attached to the frame 29 of the assembly 12 and whose rod 27 is pivotally mounted on the arm 23, opposite the axis 28 of said arm 23. Thus, thanks to the action of the cylinder 24, it is possible to remove possibly the two rollers 19,20 during the introduction of the wire 2 but especially to exert a determined pressure between the two rollers 19,20, pressure which is exerted correlatively on the flux-cored wire 2 for the purpose of its recovery.

Due to the concave curvature of the contact faces 21,22, this pressure is exerted radially over the entire surface between said contact faces and the flux-cored wire 2, so that not only does it not occur deformation or flattening annoying during this recovery, but moreover, that there is correction of the deformation or flattening that may exist on the wire, especially during its passage through independent drive means and upstream rectification means.

In order to obtain the desired straightening, it is necessary for a given cored wire to exert overall a determined pressure. Thanks to the application of the pressure according to a surface of contact, it is thus possible to reduce the number of sets of pressure rollers. A satisfactory result is nevertheless obtained with a larger number of sets of pressure rollers and the application of the pressure in the form of two continuous lines for each roll, for example the cored wire coming into contact with the two oblique walls of a roll. peripheral groove of triangular section made in the roll.

The contact faces 21, 22 may have a certain texture, symbolized by the curved lines 29 on the figure 3 , so as to increase the coefficient of friction between said faces 21,22 and the outer face of the cored wire 2, allowing optimization of its transfer and also its recovery.

During its passage between the five sets 18 of pressure rollers 19,20, the cored wire 2 takes a vertical direction. To constrain, if necessary, the wire 2 to keep this direction, it is expected, in the assembly 12, intermediate tubes 30 which extend over the entire height of the assembly 12 in the intervals between the five games 18 pressure rollers 19,20 and in the input and output portions of said assembly 12, and in which the flux-cored wire 2 passes.

Each intermediate tube 30 is fixed to the frame 29 by spacers 31. At the exit of the driver / rectifier assembly 12, the cored wire 2 enters the guide tube 13, which is strictly in the extension of the intermediate tubes 30, said guide tube 13 having a vertical direction. The function of this guide tube is both to protect the cored wire from the outside environment and to maintain the vertical direction of said cored wire during its movement towards the bath 3.

To ensure this function, the inner diameter of the guide tube 13 is of the order of 1.5 to 5 times the outer diameter of the cored wire 2.

In one embodiment, the cored wire 2 had an outside diameter of 11.5 mm and the inner diameter of the guide tube 13 was 36 mm.

To the distal end of the guide tube 13 there is provided a protective tip 14 intended to protect the said end on the one hand from the heat emitted by the bath 3 and on the other hand from molten metal projections which may occur during the introduction of the cored wire 2 in the bath 3. This protective tip is made of a thermally more resistant material than that in which is formed the guide tube 13, for example ceramic.

This protective tip 14 extends beyond the distal end 32 of the guide tube over a given distance, for example of the order of 10 to 30 cm, so that the protective tip 14 can be found itself at a relatively small distance D from the surface of the bath 3, for example of the order of 20 cm to 50 cm.

This provision is intended to allow the introduction of the cored wire 2 in the bath 3 being sure that it retains its vertical direction, without being tampered with before its introduction into the bath by the heat emitted by it. Of course, this distance D may vary depending on the driving speed of the cored wire 2, this speed can range from 40 to 400 meters per minute.

A particular embodiment of a protective tip 34 is illustrated in FIG. figure 4 . In this embodiment, the guide tube is in two parts, namely a proximal portion, not shown on the figure 4 , and a distal portion 33 on which is fixed the protective cap 34. The distal portion 33 may be connected to the proximal portion of the guide tube by removable connecting means, for example a bayonet system 35 of which only the part female is represented on the figure 4 . The advantage of this embodiment in two parts proximal and distal of the guide tube allows to replace only the distal portion and the protective tip in case of alteration thereof, due to projections and the heat emitted by the bath 3.

Claims (20)

1. Method for introducing a cored wire (2) into a bath (3) of molten metal, consisting in extracting the cored wire from a reel (9), especially from the core of the reel, and in making it run into the bath of metal (3), one part of the path travelled by the cored wire being formed in a guide tube (13) that is disposed vertically above the bath and whose distal end (32) is at a defined height (H) above the surface (PP') of the bath of metal (3), characterized in that the cored wire (2) is driven and subjected to a straightening operation, under conditions practically not altering its substantially circular cross-section and allowing it to be introduced and penetrate into the depth of the bath (3) in a vertical direction, the straightening operation is carried out by the passage of the cored wire (2), before its entry into the guide tube (13), through a plurality of sets (18) of two press rolls (19, 20), the contact between the cored wire and each press roll being:

   - either along a contact surface, the contact faces (21, 22) of the press rolls with said wire (2) being concave, or

   - along at least two lines of contact, each roll including a peripheral groove of triangular cross-section whose oblique walls delimit the contact faces with the cored wire.
2. Method according to claim 1, characterized in that the radius of curvature of the concave faces (21, 22) of the press rolls is substantially the same as that of the cored wire (2).
3. Method according to claim 1 or 2, characterized in that the cored wire is held laterally during its passage between the sets (18) of press rolls (19, 20), for example by interposed guide tubes (30).
4. Method according to any one of claims 1 to 3, characterized in that the driving of the cored wire is carried out at the same time as its straightening, in particular some of the press rolls (19) being drive rolls.
5. Method according to any one of claims 1 to 3, characterized in that the driving of the cored wire is carried out upstream and independently of its straightening, and in that during the straightening operation the cored wire (2) extends in a vertical direction.
6. Method according to any one of claims 1 to 5, characterized in that the ratio between the inside diameter of the guide tube, and optionally of the interposed tubes, and the outside diameter of the cored wire is of the order of 1.5:1 to 5:1.
7. Method according to any one of claims 1 to 6, characterized in that it further consists in protecting the distal end (32) of the guide tube (13), and preferably the cored wire (2) on its path beyond said end (32), in proximity to the bath (3), by a protective end-piece (34).
8. Installation (1) for introducing a cored wire (2) into a bath (3) of molten metal, comprising:

   - driving means (12) for driving said cored wire, from a reel (9) in which the wire is extracted from the core of the reel;

   - a guide tube (13) for guiding the cored wire (2) the distal end (32) of which tube is at a defined height (H) above the surface of the bath (3),

   characterized in that the guide tube (13) extends in a vertical direction and in that it includes straightening means (12) for the cored wire (2), disposed before its entry into the guide tube (13) and capable of imparting a straight direction to the cored wire (2) without altering its circular cross-section and optionally while correcting the deformation present on said cross-section, the straightening means consisting of a plurality of sets of two press rolls, the contact between the cored wire and each press roll being:

   - along a contact surface, the contact faces (21, 22) of the press rolls with said wire (2) being concave, or

   - along at least two lines of contact, each roll including a peripheral groove of triangular cross-section whose oblique walls delimit the contact faces with the cored wire.
9. Installation according to claim 8, wherein the contact between the cored wire and each press roll is along a contact surface, characterized in that the straightening means are formed by a limited number, for example from three to five, sets (18) of two press rolls (19, 20).
10. Installation according to claim 8 or 9 wherein the contact between the cored wire and each press roll is along a contact surface, characterized in that each contact face (21, 22) with the cored wire of each roll has a radius of curvature which is substantially the same as that of the cored wire (2).
11. Installation according to one of claims 8 to 10 wherein the contact between the cored wire and each press roll is along a contact surface, characterized in that each contact face of each roll corresponds to an angular portion of between 120° and 180°.
12. Installation according to claim 10, wherein the contact between the cored wire and each press roll is along two lines of contact, characterized in that the straightening means are formed by a large number, for example from twelve to twenty, of sets of press rolls.
13. Installation according to any one of claims 8 to 12, characterized in that it includes interposed guide tubes (30) for guiding the cored wire (2) between each pair (18) of sets of press rolls (19, 20).
14. Installation according to any one of claims 7 to 13, characterized in that the ratio between the inside diameter of the guide tube (13), and optionally of the interposed tubes (30), and the diameter of the cored wire is of the order of 1.5:1 to 5:1.
15. Installation according to any one of claims 7 to 14, characterized in that the distal end (32) of the guide tube (13) is provided with a protective end-piece (14) more heat-resistant than said guide tube (13).
16. Installation according to claim 15, characterized in that the protective end-piece (14) extends beyond the distal end (32) of the guide tube (13) for a given distance, for example of the order of 10 to 30 cm.
17. Installation according to either claim 15 or claim 16, characterized in that the guide tube is in two parts, one proximal and the other distal (33) to which the protective end-piece (34) is fixed, and in that the two said parts are firmly connectable by detachable connecting means, especially by a screw thread or by a bayonet system (35), so as to permit the replacement of the assembly formed by the distal part (33) of the tube and the protective end-piece (34).
18. Installation according to any one of claims 7 to 17, characterized in that the straightening means serve as driving means.
19. Installation according to claims 8 and 18, characterized in that each set (18) of two rolls (19, 20) comprises a driven roll (19) and an idle roll (20), and in that the idle roll (20) is mounted on a pivoting arm (23), forming a rocker arm, movable by a jack (25).
20. Installation according to any one of claims 8 to 19, characterized in that the driving means are upstream of the straightening means and in that, in the straightening means, the cored wire extends in a vertical direction.

Images