Refractory plate for slide gate and the slide gate

Abstract: The present invention concerns a plate for a slide gate with indentation. The plate is characterized in that it is asymmetric relative to its axes (XX, YY) so as to cooperate with a complementary form (34) of the indentations in order to define an aligning device that permits it to be mounted only in one position in the upper indentation (14) and in only one position in the lower indentation (18). The combination of both the plate and the slide gate permit efficient and safe recycling of the plates after a step of cleaning, repairing or reconditioning of the plate surface.

Description: The present invention concerns a refractory plate for slide gate closure, and the closure itself. To control the flow of molten steel through the bottom of a metallurgical container such as a steel making ladle, a slide closure is generally used. It involves an upper fixed refractory plate connected by a joint which is generally cemented to an internal nozzle located in the thickness of the refractory that covers the wall of the bottom of the metallurgical container, and a mobile lower plate connected to a collecting nozzle or to a jet protection tube, also through a generally cemented joint. These plates wear rapidly such that it is necessary to replace them frequently. In order to reduce the cost of refractories per ton of cast steel, it is known to use the same plates several times, possibly after cleaning or reconditioning. For example, the patent STOPINC FR 2,625,928 accessorily describes a plate with two pouring holes, rectified on its two faces and equipped with a metal bandage. This plate is turned upside down and reused. However, a problem that is posed in the familiar processes is that of human management. The operator does not know how many times the plates have been reused. The information should be stored ; the history of the plates should be noted. This necessitates a monitoring of the plates, which is difficult. The efficacy of recycling is reduced. Furthermore, a plate that has been used has damaged zones, e.g., eroded and abraded zones. Its reuse introduces risks, e.g. of the infiltration of metal between the two plates. Reuse of the plates, advantageous in the sense that it lengthens the service life of the refractories, also involves the disadvantage of introducing risks. The parent application proposes a process for reusing slide gate refractory plates, the closure having an upper indentation and a lower indentation for receiving a set of two refractory plates, each of these plates resting in an indentation through a face that becomes its support face and cooperating with the other plate through a face that becomes its sliding face. This process permits a simple management of the plates and it also permits prolonging the service life of the refractories by reducing the risks associated with this prolongation. It is characterized in that a set of refractories comprised of a new plate associated with a plate that has been used only once in the slide closure, and in that during the changing of the plates, the new plate is mounted in a lower or upper loading indentation, this indentation remaining the same for each plate change, the plate used once being mounted in the other indentation (recycling). This process thus defines a charging indentation of new plates, always the same, and a charging indentation of plates used only once, also always the same. Thus, the management of the plates is simple. During a reconditioning of the slide gate the operator knows, in view of the indentation in which it was placed, which is used for the first time and which should be recycled, and which plate has been used for the second time and should be discarded. The operator systematically discards the recycled plate and keeps the plate that has been used once in an appropriate place so that it can be recycled. He then systematically mounts a new plate in the charging indentation, always the same, of new plates and a recycled plate in the other indentation. Furthermore, this process is very reliable. In effect : each plate is used twice and only twice ; each face of the plate is used as a slide face once and only once ; the sliding surfaces are systematically new ; two reused plates are never simultaneously present in the slide closure. A set of two recycled plates is thus never used. According to a preferred embodiment, the plate used once is placed in the recycling indentation such that the face that was its support face during its first application becomes its sliding face. Depending on the casting mode used, it can be of interest to mount the new plate either in the upper position or in the lower one. According to one embodiment, the new plate is mounted as the lower plate and the reused plate is the upper plate. Thus, closure and regulation is always with a new plate. Security is optimal because the lower plate is important for the closure of the pouring orifice. According to another embodiment, the new plate is used as a upper plate. Thus, the joint between the internal nozzle and the plate is made on new surfaces. The present invention concerns a refractory plate designed to be mounted in an indentation of a slide closure for a metallurgical container such as a ladle or a tundish, this slide closure having an indentation for the upper plate and an indentation for the lower plate. The object of the invention is to provide a refractory plate with an aligning device that permits it to be mounted in only one position in each indentation. This object is achieved with the refractory plate defined in claim 1. Thus, when the recycled plate is mounted, one is certain that it is placed correctly, that is, so that its support face becomes its sliding face and vice versa. The plate is possibly ringed or has a metal envelope. In this case, its smaller face is at least equal to 60 % of the other face. It can have two or more tapholes. The invention also concerns a slide gate for a metal container as defined in claim 4. Other characteristics and advantages will be manifested in reading the following description of exemplary embodiments that are provided by means of illustration with reference to the attached Figures. Figure 1 is a cross-sectional view of a slide gate and can be equipped with plates according to the present invention; Figures 2a, 2b and 2c present three stages of the parent invention process; Figure 3 is a top view of a plate according to the invention having an aligning device; Figure 4 is a cross-section view of a plate according to the present invention and having a means for preventing a mounting more than once in the same indentation; Figure 5 is a top view of the plate shown in Figure 4 after an initial use; Figure 6 shows the circulation of the plates. Figure 1 shows a cross-sectional view of a slide gate for a metallurgical container such as a steel-making ladle or a distributor. The gate 2 is mounted under a bottom wall 4 covered with a layer of refractory material 6. The slide gate has a fixed underframe 8 mounted under the plate 4 and a door 10 that can be mounted to pivot relative to the fixed underframe 8. A fixed upper plate 12 is mounted in an indentation 14 of the upper underframe 8. A lower mobile plate 16 is mounted opposite the fixed plate 12. The plate 16 is seated in an indentation 18 of a slide 20. The slide 20 can be displaced in a known manner relative to the fixed part of the slide gate in order to regulate or stop the flow of molten metal. The upper fixed plate 12 is connected to an internal nozzle 13 that passes through the layer of refractory material 6 and has an axial channel for the passage of the molten metal. The mobile lower plate 16 is connected to a collecting nozzle 21. The two plates are symmetrically identical. Each of the fixed 12 and mobile 16 plates has a circular hole 22 for the passage of molten metal. In the exemplary embodiment shown the plates 12 and 16 are ringed. In a variant, these plates could also be surrounded by a metal envelope in a known manner, or have neither ringing nor metal envelope. The plates 12 and 16 have identical plane faces. These faces are not distinguished from each other when they are not mounted in the slide gate. On the other hand, when the plates have been put in place, they each have a support face with which they rest on the bottom of the indentation in which they are seated (upper indentation 14 or lower indentation 18). Each plate also has a sliding face, also called a working face. During pouring, these working faces makes it possible to regulate the flow of metal. They rub permanently against each other and wear rapidly. Consequently, it is necessary to change them frequently. According to the process described in the parent application, a new plate is systematically mounted in the lower indentation 18 of the slide 20. After being used only once, the lower plate 16 is recovered and mounted in the indentation 14 of the upper underframe 8. It is positioned so that the face that was its working face when it was positioned in indentation 18 becomes its support face in the upper indentation 14. Reciprocally, the face that was its support face becomes its sliding or working face. This face is new in the sense that it was never used as a sliding face. The portion of it that surrounds the taphole was utilized to effect a joint with the nozzle 21, but no wear occurs on the surface in question. The upper plate 12 that had already been used once as the lower plate is simply discarded. For the orifice of metal passage 22 of the lower plate 16 to be located opposite the axial channel of the internal nozzle 13, it is necessary to pivot it 180° in the horizontal plane since the hole 22 is off-centered relative to the plate. Figures 2a, 2b and 2c illustrate the successive stages of the reutilization process described in the parent application. In Figure 2a plate A is the upper plate and plate B is the lower plate before the metal is poured. The face of the plate A that had already been used is indicated by hatching 24. This face serves as the support face in the indentation 14 (see Figure 1). The other face of plate A constitutes its working face. It had never been used. The lower plate B is new, none of its faces have been used. Figure 2b shows the plates A and B after one cycle of pouring, e.g., some dozen ladles, before these plates had been replaced. The two faces of the upper plate A have been used, as indicated by the hatchings 24 and 26. Only one face of the lower plate B has been used, its upper face in the example shown, as indicated by the hatching 28. Plate A is discarded and plate B is mounted as the upper plate. A new plate C is mounted as the lower plate. The situation is then as shown in Figure 2c, which is identical to that shown in Figure 2a, with the sole exception that plate B occupies the position that was that of plate A in Figure 2a and plate C the plate that was that of plate B. The cycle thus continues in the same manner. In the example described with reference to Figures 1 and 2, a new plate is placed in the lower position. However, it is also possible according to the invention to place the new plate in the upper position and then reuse it as the lower plate. The lower plate undergoes a more intense erosion because it laminates or flattens the metal. This is why the upper plate is less eroded than the lower plate. Figure 3 shows a top view of a plate according to the present invention, which has an aligning device. This plate has a circling 30. The aligning device is comprised of a cut panel 32. The plate is thus asymmetric relative to each of its axes XX and YY. The profile of the plate in the absence of a cut panel is designated by 34. 14 and 18 indicate the form of the upper or lower indentation. As can be seen, this form follows the periphery of the plate at the level of the cut panel 32 so that the latter can be mounted only in a single position. Of course, the position of the plate in the upper indentation is different from its position in the lower indentation, such that the support face of the plate becomes its working face. However, in the mode of implementation shown in Figure 3 there is nothing to prevent mounting an already used plate instead of a new plate in the lower indentation. The implementation mode of Figures 4 and 5 remedies this shortcoming. Figure 4 shows a cross-sectional view of a preferred mode of implementation of a plate according to the invention. This plate has a means for preventing the mounting more than once in one of the indentations 14 or 18 of the slide gate. In the example shown this means is comprised of a slug 44 and a spring 42 that is capable of forcing the slug 44 out of a recess 40 provided in the thickness of the plate 12 or 16. The slug 44 is retained by a thermofusible substance. During the pouring of steel, under the effect of the heat of the molten metal, the plate 12 or 16 is heated and the thermofusible element melts, which frees the slug 44. The slug 44 then comes in contact with the indentation (the indentation 18 in the example shown on Figure 4). When the plate 16 is removed from this indentation, the slug 44 projects out completely and prevents the placement of the plate 16 in the indentation 18 a second time. On the other hand, the upper indentation 14 has a slot 46 capable of accepting the slug 44 (see Figure 5). The plate 16 can then be mounted without difficulty in this indentation after pivoting 180° in the horizontal plane. Thanks to this device, the operator is systematically forced to mount a new plate in the desired indentation, the upper indentation 14 in the example described in Figure 4. On the other hand, there is nothing to prevent the simultaneous mounting of two new plates, e.g., if there should not be any used plates. The means that prevents mounting the plate more than once in the same indentation can be situated on the longitudinal axis XX of the plate, as in Figures 4 and 5. However, it is preferably located outside of this axis so that the plate is asymmetric relative to each of its axes XX and YY. In this manner, the means can also play the role of aligning device shown in Figure 3. For example, when the plate is new, it projects out so as to penetrate into a shallow recess in the lower indentation. After an initial use of the plate, the slug moves out more and can no longer enter into the recess of the lower indentation. On the other hand, the recess 46 of the upper indentation is sufficiently deep to receive it. The circulation of the plates is shown in Figure 6. A box 50 contains new plates, which are mounted in the lower indentation of the gate 2. The box 52 contains plates that were used a single time. These plates are mounted in the upper indentation of the gate 2. The gate is then ready for a pouring cycle. After pouring, the gate is opened and the plates are withdrawn. The lower plate, used once, is recovered in the box 54. It is given a cleaning in 56, and then goes into box 52. The upper plate, which was used twice, is discarded into the garbage can 58. According to another of its aspect, the invention relates therefore to a process comprising a step of cleaning a used refractory plate. The invention plate can also have more than one hole, e.g., two. This offers the advantage of having a new pouring hole when the plate is reused. The surfaces that produce the joint with the internal nozzle and with the collecting nozzle respectively are also new. The cleaning of the plate is facilitated. The plate can be reused so that its old support face becomes its sliding face and vice versa. But the same face can also be reused as the support face or as the sliding face provided these are different working zones of the plate.

Claims: Refractory plate for use in a slide gate (2) for a metallurgical container, such as a ladle or a distributor, characterized in that the periphery of the refractory plate (12,16) is asymmetric relative to its axes (XX, YY). Plate (12, 16) according to claim 1, characterized in that the asymmetry of the refractory plate is comprised of a cut-off (32). Plate (12, 16) according to claim 2, characterized in that the plate is circled with a metal ring or has a metal envelope. Slide gate (2) having an indentation (14) for an upper refractory plate (12) and an indentation (18) for a lower refractory plate (16), characterized in that these indentations present a form, the periphery of which is asymmetric relative to their axes (XX, YY). Use of a refractory according to any one of the claims 1 to 3, comprising a step of cleaning the faces of the plate.

Inventors: HANSE ERIC, RICHARD FRANCOIS-NOEL, HANSE, ERIC, RICHARD, FRANCOIS-NOEL
Applicants: VESUVIUS FRANCE SA, VESUVIUS FRANCE (S.A.)
Application year: 1996
Main classification: B22D41
IPC codes: B22D41, B22D11