EP0053070A1 - Metallurgical ladle for inductive treatment of metals - Google Patents

Abstract

Metallurgical pocket for inductive treatment of metals. The pocket is internally lined with a refractory lining 1 and its enclosure 2, of generally tubular shape, is formed, in the heating zone, by longitudinal metal tie rods 4, electrically isolated from each other and protruding longitudinally above and below. of the heating zone. The pocket comprises an upper box 15 and, optionally, a lower box 16, of generally annular shape, respectively at the upper part and at the lower part of the enclosure 2. The tie rods 4 are held in place by connecting means 10 , electrically insulating, between the ends of the tie rods 4 and the upper box 15 and, optionally, the lower box 16. The tie rods 4 preferably have axial internal conduits communicating with the interior of the upper box 15 and that of the lower box 16 to allow the circulation of the cooling fluid. The bag according to the invention allows powerful inductive treatments of metals and alloys, and in particular steel.

Description

The present invention relates to a metallurgical ladle with a fragmented metal enclosure, intended for the inductive treatment of metals and alloys and in particular steel.

The production practices of metals, and of steel in particular, are increasingly oriented towards metallurgy "out of the furnace" or "pocket metallurgy". Such a solution comes up against the delicate problem of heating the metal in the ladle. Electric induction heating has the advantage of transmitting energy within the metallic charge with excellent thermal efficiency. However, this heating causes undesirable eddy currents in the metal parts of the enclosure. It follows that the enclosure is overheated and that, after a certain number of operations, it loses its mechanical strength due to excessive thermal stresses. On the other hand, the enclosure of the pocket must withstand the high pressure exerted by the molten metal.

Thus, it is necessary to produce a metallurgical ladle which satisfies two necessities: on the one hand, to avoid overheating by eddy currents in the massive parts placed in the magnetic heating field, and, on the other hand, to ensure a mechanical resistance of the pocket.

To this end, French patents No. 2,366,079, No. 2,368,542, No. 2,368,543, No. 2,368,326 and No. 2,370,797, in the name of the applicant, offer metallurgical bags of the type mentioned above -above. More particularly, French Patent No. 2,370,797 describes a metallurgical ladle, a schematic vertical section of which is shown in the appended figure.

As can be seen in FIG. 1, the pocket of the prior type is lined with a refractory lining 1. The metal enclosure 2 of the pocket is fragmented: it is formed, in the heating zone, that is to say opposite the inductor windings 3, by metal tie rods = longitudinal and hollow, so as to allow the passage of a cooling fluid. The tie rods 4 are held in place between two annular flanges, respectively upper 5 and lower 5 ', which are rigidly connected to a ferrule 6 and to the bottom 7 of the pocket.

The ferrule 6 serves as a hoop at the upper end of the pocket and has two crowns, respectively upper 8 and lower 9, the lower ring 9 serving to support the pocket during its installation in an induction heating tank.

The tie rods 4 are connected to the flanges 5 and 5 ′ by connection means 10 and have an axial internal conduit 11 which is connected to the zone 12 delimited by the crowns 8 and 9 via the connecting means 10 and a sealed extension 13. The cooling fluid is introduced at the lower end of the tie rods 4, rises in the conduit 11 and escapes into the zone 12.

The applicant studied the thermal evolution of the metal parts of a pocket of this type during an intensive treatment of inductive heating. Indeed, it is necessary to carry out intensive heating treatments (greater electrical power used and longer heating time). However, during such treatments, it is necessary to avoid excessive heating of the metallic parts of the bag.

To study this thermal evolution, five thermoelectric couples were implanted in different parts A (upper flange), B (bottom), C (ferrule), D (lower flange) and E (pulling) from the pocket, indicated on the figure 1. The attached figure 2 represents the results of this experiment.,

In this figure` 2, we have represented the curves giving the temperature (in ° C) as a function of time (in hours) for the different parts of the pocket (A, B, C, D, E).

As can be seen from these curves, the highest temperature of the bag (450 ° C.) is noted on the upper flange 5 although the latter is located outside the heating zone. The temperature reached by the lower flange 5 ′ and the ferrule 6 is significantly lower (350 ° C). The temperature of the bottom 7 and of the tie rods 4 remains low (150 ° C.), which confirms the efficiency of the internal cooling described above.

These experiments have therefore shown that the pocket described above is usable for medium-order heating but that, for more powerful heating, the thermal stresses resulting from the rapid heating of the flanges pose serious problems.

The object of the present invention is precisely to propose a metallurgical ladle, the solid metal parts of which do not overheat during high-power heating treatments and which at the same time has _" good mechanical strength.

To this end, the subject of the invention is a metallurgical ladle for the inductive treatment of metals, internally lined with a refractory lining and whose enclosure, of generally tubular shape, is constituted, in the heating zone, by metal tie rods longitudinal, electrically insulated from each other and protruding longitudinally above and below the heating zone, the tie rods being held in place by tightening at the upper part and at the lower part of the enclosure.

According to the invention, the upper part of the enclosure is constituted by a box of generally annular shape and the tie rods are held in place at the upper part of the enclosure by connecting means, electrically insulating, between the upper ends of the tie rods and the bottom of the box.

According to one embodiment of the invention, the lower part of the enclosure also consists of a box of generally annular shape which bears on the bottom of the pocket. The tie rods are also held in place at the lower part of the enclosure by electrically insulating connection means between the lower ends of the tie rods and the ceiling of the lower box.

According to a preferred embodiment of the invention, the connecting means consist of threaded connecting pieces at one of their ends and passing through openings in the bottom of the upper box and possibly in the ceiling of the lower box . The threaded ends of these parts are screwed into threads formed in the corresponding ends of the tie rods.

According to a first alternative embodiment, each of the assembly parts consists of a threaded rod at its two ends. One of these ends is intended to be screwed into the thread of the corresponding tie rod and the other is intended to be screwed into a flange nut.

According to a second alternative embodiment, each of the assembly pieces consists of a rod, one of the ends of which ends in a base and the other of which is threaded. The threaded end is intended to be screwed into the thread of the corresponding tie rod while the base is clamped against the internal face of the bottom of the upper box and possibly against the internal face of the ceiling of the lower box.

According to a characteristic of the invention, each of the tie rods has an internal conduit, to allow the circulation of a cooling fluid. This duct communicates tightly with the interior of the box. To achieve an upward circulation of the cooling fluid, the lower box is connected to a cooling fluid supply source and the upper box has an opening for the outlet of the fluid outside of the pocket. Of course, a downward circulation of the cooling fluid can be achieved by connecting the upper box to a source of fluid supply and by making an outlet opening for the fluid in the lower box.

As can be understood, the device according to the invention has the advantage, compared to the bag of the prior type described above, that the upper and lower boxes are likely to be cooled quickly. Thus, the drawbacks due to the excessive heating of the flanges of the pocket of the previous type are avoided. In addition, the upper and lower boxes of the pocket according to the invention fulfill the function of holding in place and tightening the tie rods thanks to the special provisions of the connecting means between the tie rods and the boxes. Furthermore, the assembly and disassembly of the tie rods is easily carried out, as will be seen below.

• - la figure 3 représente une coupe verticale d'un mode de réalisation de la poche conforme à l'invention,
• - la figure 4 représente une vue en élévation de ce mode de réalisation,
• - la figure 5 représente une coupe longitudinale d'un tirant muni de ses moyens d'assemblage avec les caissons supérieur et inférieur, conformément à une variante de l'invention.

The invention will be clearly understood and the advantages which it provides will become clear from the description which follows, given with reference to the appended drawings in which:

• FIG. 3 represents a vertical section of an embodiment of the bag according to the invention,
• FIG. 4 represents an elevation view of this embodiment,
• - Figure 5 shows a longitudinal section of a tie rod provided with its means of assembly with the upper and lower boxes, according to a variant of the invention.

In all the figures, identical elements will be designated by the same reference. Furthermore, in FIGS. 3, 4 and 5, the elements identical to those of the bag of the previous type will be designated by the same references as those indicated in FIG. 1.

As seen in Figures 3 and 4, the pocket is lined internally with a refractory lining 1. The enclosure 2 of the pocket is formed in the inductive heating zone, that is to say in the part of the middle, by a large number of metallic tie rods 4. These tie rods 4 are made of non-magnetic material, for example non-magnetic stainless steel, so as not to channel the incident magnetic field lines to the detriment of the load to be treated. As can be seen in FIG. 4, the tie rods 4 are distributed regularly around the refractory lining 1. The spaces formed between two consecutive tie rods 4 are occupied by seals 14 made of refractory material.

The enclosure has an upper box 15 at its upper part and a lower box 16 at its lower part. Each of these boxes 15 and 16 is made up respectively of a ferrule 17 and 18 enveloping the refractory lining 1, of a ceiling 19 and 20, of a bottom 21 and 22 and of a wall 23 and 24. These various elements respectively define an interior space 25 and 26 of generally annular shape. The tie rods 4 are held in place by tightening between the upper box 15 and the lower box 16 by means of assembly 10.

As can be seen in FIG. 4, the upper box 15 has lateral pins 27 for the usual handling operations. The upper box 15 has, in addition to the function of tightening and maintaining the refractory lining 1, that of supporting, thanks to its bottom 21, the pocket during the installation of the latter in the induction heating tank.

The boxes 15 and 16 preferably have openings 28 called "manholes" in their walls 23 and 24 to allow access to the assembly means 10. When the bag is put into service, the holes 28 men are blocked.

In the example shown in FIGS. 3 and 4, a supply duct 29 supplies the lower box 16 with pressurized cooling fluid which generally is air. This fluid rises in the internal conduits I1 of the tie rods 4 and spreads inside 25 of the upper box 15. Then, the fluid escapes outside the pocket through the opening 30 provided for this purpose in the box. higher 15.

As can be seen in FIG. 5, the tie rods 4 are held by clamping between the bottom 21 of the upper box 15 and the ceiling 20 of the lower box 16 by means of the assembly means 10. Each of the tie rods 4 consists of 'a tubular rod 31, the ends 32 of which are internally threaded and bear on the external face of the bottom 21 of the upper box 15 and on the external face of the ceiling 20 of the lower box 16. These supports are provided by means of washers support 33 and flat annular seals 34.

The assembly means 10 consist of a stud, the threaded rod 35 of which passes through an opening 36 provided for this purpose in the bottom 21 of the upper box 15 and in the ceiling 20 of the lower box 16. The threaded rod 35 is thus screwed into 1 = thread 32 of the corresponding tie rod 4. The assembly means 10 can be either a single piece stud, that is to say a rod ending at one of its ends by a thread and at the other by a base secured to the rod 35, either by a stud consisting of two parts separable from one another. The one-piece stud is more convenient for the assembly and disassembly of the tie rods 4. On the other hand, it is less easy to machine. In any case, the stud must have an internal conduit, so as to allow the passage of the cooling fluid.

In the embodiment shown in FIG. 5, the assembly means 10 consist of two separable parts. The tubular rod 35 is threaded at its two ends. One of these ends is screwed into the thread 32 of the tie rod 4, and the other is engaged in a nut with base 37 by screwing, which allows the tightening of the tie rod 4 between the bottom 21 and the ceiling 20 of the boxes 15 and 16. The tightening of the nuts 37 is ensured against the internal face of the bottom 21 and the internal face of the ceiling 20 by l 'intermediate support washers 33' and flat annular seals 34 'identical to the support washers 33 and flat annular seals 34 described above.

The openings 36 formed for the passage of the assembly means 10 in the bottom 21 of the upper box 15 and in the ceiling 20 of the lower box 16 have a diameter slightly greater than that of the threaded rods 35 which pass through them, so as to be able to place an annular seal 38 of the "cannon" type.

Joints 33, 34, 33 ', 34' and 38 are above all good electrical and thermal insulators. They must also exhibit good resistance to temperature which can, where they are plastered, reach several hundred ° C., and good resistance to compression due to the inevitable expansions of the metallic structure during the commissioning of the pocket. Given all these requirements, the applicant recommends the use of a material sold under the name of "Syndanio", which is composed of a mixture of mineral stones and asbestos previously ground.

In the embodiment described, the tie rods 4 and the corresponding studs 35 respectively have internal conduits II and 39 communicating with each other, so as to constitute passages for the cooling fluid between the interior 26 of the lower box 16 and the interior 25 of the upper box 15.

As mentioned above, the cooling fluid coming from a power source (not shown in FIG. 5) enters via line 29 in the lower box 16. It then circulates in the lower box 16, the tie rods 4 and the upper box 15 (via the conduits 11 and 39), cools them, then escapes outside the pocket through the opening 30 made in the upper box 15.

In the above description, the circulation of the cooling fluid is ascending, but it is also possible to produce a descending circulation. In this case, the upper box 15 is connected to a fluid supply source and the lower box 16 has an opening for letting the fluid exit outside the pocket.

• Tout d'abord, on ouvre les trous d'hommes 28 et 28'. Puis, on retire les écrous 37 supérieur et inférieur. Ensuite, on dégage les rondelles d'appui 33' et les joints plats 34'. Un méplat 40, usiné sur la partie lisse de la tige 35 à un endroit tel qu'il est accessible après dégagement des rondelles 33' et joints 34' précités, permet le dévissage de la tige 35 au moyen d'une clef appropriée. On dégage ainsi les tiges 35 des taraudages internes 32 du tirant 4 correspondant. Le tirant 4 peut alors être dégagé par simple traction latérale. Les opérations de remontage s'effectuent dans un ordre inverse à celui qui vient d'être décrit.

The disassembly of each of the tie rods 4 is carried out as follows:

• First, we open the manholes 28 and 28 '. Then, remove the upper and lower nuts 37. Then, the support washers 33 'and the flat seals 34' are released. A 40 flat, machined on the part smooth of the rod 35 in a location such that it is accessible after release of the washers 33 'and seals 34' above, allows the unscrewing of the rod 35 by means of an appropriate key. The rods 35 are thus released from the internal threads 32 of the corresponding tie rod 4. The tie rod 4 can then be released by simple lateral traction. The reassembly operations are carried out in reverse order to that just described.

Thus, the invention has this additional advantage that the operation of replacing defective or used tie rods 4 is easy. Indeed, the assembly or disassembly of the enclosure 2 can be carried out at the level of the manholes 28 and 28 ′ without disassembling the boxes 15 and 16. During this operation, it is also possible to precisely adjust, tightening the tie rods 4 between the upper 15 and lower 16 boxes.

It goes without saying that the present invention cannot be limited to the particular embodiments described. Thus, the particular technology of the tie rods described with reference to FIG. 5, can be replaced by any other technology, the main thing being that the means of assembly of each of the tie rods with the upper box and, possibly, the lower box, are electrically insulating and keep the tie rods in place.

Similarly, the nature of the cooling fluid (air) is in no way limiting. It is also possible to use another gas, and even a liquid, for example water. In the latter case, it will be desirable to provide a collector at the place where the liquid is discharged.

Claims (9)

1. Metallurgical pocket for the inductive treatment of metals, internally lined with a refractory lining and whose enclosure (2), of generally tubular shape, is constituted, in the heating zone, by longitudinal metallic tie rods (4), insulated electrically between them and protruding longitudinally above and below the heating zone, the tie rods (4) being held in place by tightening at the upper part and at the lower part of the enclosure (2), characterized in that that the upper part of the enclosure (2) is constituted by a box (15) of generally annular shape, the retention of the tie rods (4) at the upper part of the enclosure (2) being ensured by connecting means ( 10), electrically insulating, between the upper ends of the tie rods (4) and the bottom of the box (15). 2. metallurgical pocket according to claim 1, characterized in that the lower part of the enclosure (2) is constituted by a box (16) of generally annular shape, bearing on the bottom (7) of the pocket, maintaining tie rods (4) at the lower part of the enclosure (2) being provided by connecting means (10), electrically insulating, between the lower ends of the tie rods (4) and the ceiling of the box (16). 3. metallurgical ladle according to one of claims 1 or 2, characterized in that the connecting means (10) consist of assembly parts threaded at one of their ends and passing through openings (36) formed in the bottom of the upper box (15) and / or in the ceiling of the lower box (16), the threaded ends of the parts being screwed into threads (32) formed in the corresponding ends of the tie rods (4). 4. metallurgical ladle according to claim 3, characterized in that each of the assembly parts (10) consists of a threaded rod at its two ends, one of these ends being capable of being screwed into the thread ( 32) of the corresponding tie rod (4) and the other being capable of being screwed into a flange nut. 5. Metallurgical ladle according to claim 3, characterized in that each of the assembly parts (10) consists of a rod, one of the ends of which ends in a base and the other of which, threaded, is capable of '' be screwed into the thread (32) of the corresponding tie rod (4), thus causing the base to be tightened against the internal face of the bottom of the upper box (15) and / or the internal face of the ceiling of the lower box (1 ₆ ). 6. Metallurgical pouch according to one of claims 1 to 5, characterize _s ed in that each of the tie rods (4) has an internal conduit (11) for circulation of a cooling fluid, said duct (11) communicating sealingly with the interior of the box (15) and / or (16). 7. metallurgical ladle according to claim 6, characterized in that the interior of the lower casing (16) is connected to a source of supply of cooling fluid and the upper casing (15) has an outlet opening (30) for the fluid cooling outside the pocket. 8. metallurgical ladle according to claim 6, characterized in that the interior of the upper box (15) is connected to a source of supply of cooling fluid and the bottom box (16) has an outlet opening of the coolant to the outside the pocket. 9. metallurgical pocket according to one of claims 1 to 8, characterized in that the wall of the box (15) and / or (16) has openings (28) for access to the connecting means (10), said openings (28) being capable of being closed when the bag is put into service.

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