LU88701A1 - Continuous casting mold and sealing element for continuous casting mold - Google Patents

Description

Continuous casting mold and sealing element for continuous casting mold.

The invention relates to a sealing element for sealing an annular gap between a vibrating pouring tube and a fixed housing component of a continuous casting mold. The invention also relates to a continuous casting mold with at least one such sealing element.

During the continuous casting of steel strands, the molds are oscillated in the casting direction to prevent the strand from sticking to the cooled inner walls of the pouring tube. These vibrations of the mold can, for example, have a frequency of a few Hertz and an amplitude of more than 10 mm, the vibrating mass making up several tons. The oscillation of the mold therefore requires a very high level of performance. From this it follows that it is desirable to keep the vibrating mass as small as possible.

A classic vibrating device comprises a vibrating table on which the continuous casting mold is arranged as a unit. In the international patent application WO 95/03904, however, a mold is described which has a fixed housing with an integrated rocker arm. The pouring tube is carried in this mold by the rocker arm and is connected to an outer, fixed housing via two elastically deformable, ring-shaped sealing membranes so that it can vibrate in the housing along the pouring axis. The annular sealing membranes seal an annular pressure chamber for a cooling liquid around the pouring tube. With this mold, the mass of the parts to be oscillated and thus the effort required are greatly reduced.

Patent application WO 95/03904 proposes both metallic and rubber-elastic ring membranes. These ring diaphragms are subject to extremely complex mechanical loads. First, you have to endure a cooling water pressure of at least 5 bar, which already leads to significant tensile stresses in the ring membrane. They are also vibration loads with a frequency of several hundred

Vibrations per minute exposed, whereby the vertical stroke movements of the pouring tube cause large tensile stress peaks in the ring membrane. Furthermore, the strand can exert horizontal tensile forces on the pouring tube, which can stress the ring membrane. Under these complex loads, signs of fatigue on the ring membranes can be expected relatively quickly.

The object of the present application is to create an improved sealing element for sealing an annular gap between a vibrating pouring tube and a stationary housing component of a continuous casting mold from a flexible material.

This object is achieved in that the sealing element forms an encircling bulge whose convex side is arranged on the pressure side when the sealing element is installed.

The sealing element according to the invention is structurally much more suitable for absorbing the extremely complex mechanical stresses in the continuous casting mold than the previously known flat sealing membrane branches. It shows signs of fatigue less quickly, which in turn results in a longer lifespan. This technical success can be explained approximately as follows. With an axial movement of the pouring tube relative to the stationary housing component, a deformation of the sealing element is determined, which essentially consists in a flattening of the bulge. The sealing element according to the invention is thereby stretched much less than the known flat ring membranes and is consequently subject to lower tensile stresses. Furthermore, the pressure acts on the convex side of the circumferential bulge of the sealing element and consequently essentially generates compressive stresses in this sealing element and no tensile stresses.

The sealing element according to the invention is advantageously designed as a ring membrane which is installed horizontally in the continuous casting mold. As a result of the bulging according to the invention, the material of the ring membrane does not undergo any substantial stretching in the radial or in the circumferential direction when the pouring tube moves axially. However, the sealing element according to the invention could also be designed as a pipe socket, which is installed coaxially to the casting axis in the continuous casting mold. In the design as a pipe socket, however, the material of the sealing element is slightly stretched in the region of the bulge in the circumferential direction.

The sealing element according to the invention is advantageously made of a rubber-elastic material, such as an elastomer or rubber. It advantageously comprises reinforcing inserts, for example fabric inserts. When designed as a pipe socket, such fabric inserts should have interruptions in the circumferential direction in order to take into account the extent in the circumferential direction.

The invention also relates to a continuous casting mold which comprises a vibrating pouring tube, a fixed housing and at least one flexible sealing element for sealing an annular pressure chamber for a cooling liquid between the vibrating pouring tube and the fixed housing. As described above, this flexible sealing element forms a circumferential bulge, the convex side of which faces the annular pressure chamber.

Such a mold advantageously comprises a vibrating device and a fixed support structure, the support structure carrying the vibrating device and the vibrating device carrying the pouring tube. As a result, the weight of the pouring tube is absorbed by the vibrating device and the sealing elements are no longer loaded by the weight of the pouring tube. No additional support elements need to be arranged between the housing and the pouring tube. A compact vibrating device is designed with a vibrating lever, which is articulated in the support structure and is articulated to the pouring tube. This oscillating device advantageously comprises a hydraulic cylinder as a drive. Alternatively, however, the pouring tube could also be elastically suspended in its housing by means of spring elements, so that the vibrating device does not have to perform a supporting function and only has to transmit the vibration energy to the pouring tube.

The invention proposes several solutions as to how the sealing elements according to the invention can advantageously be arranged in a continuous casting mold.

In a first embodiment, the mold has a lower and upper sealing element according to the invention, which delimit an annular pressure chamber for a cooling liquid around the entire pouring tube. This annular pressure chamber is advantageously divided by an inner sealing device with a rubber-elastic ring membrane into a lower and upper annular collector, which are connected to an inlet line or a return line for a cooling liquid. A water-conducting jacket is advantageously arranged around the pouring tube in such a way that it forms an annular gap along the pouring tube, which on the one hand opens into the lower collector and on the other hand into the upper collector.

In a second embodiment, the mold has a lower and upper flexible ring collector, which surrounds the lower or upper end of the pouring tube, these flexible ring collectors each comprising two directly opposite sealing elements according to the invention, which are arranged such that they form an annular one between them Define the pressure chamber for a coolant. Compared to the first embodiment, the cooling water content of the mold is reduced in this second embodiment. Furthermore, an electromagnetic stirring device can be arranged outside the cooling water between the lower and upper flexible ring collector.

Also in this second embodiment of the mold, a water guiding jacket can be arranged around the pouring tube in such a way that it forms an annular gap along the pouring tube, which on the one hand opens into the lower flexible ring collector and on the other hand into the upper flexible ring collector. This water jacket is then designed as a pressure jacket between the ring collectors.

In all molds, to absorb horizontal forces acting on the pouring tube, at least one guide element can be arranged between the oscillating pouring tube and the fixed housing in such a way that it limits the pivoting out of the pouring tube in at least a first direction. This guide element is advantageously bonded to the vibrating pouring tube or the fixed housing via at least one swivel joint. To avoid tensile stresses in the guide element, this swivel joint can have, for example, a horizontal play which allows the guide element to be displaced horizontally in a second direction, which is opposite to the first direction. Alternatively, however, the guide element can also be mounted in at least one swivel joint in an elastically compressible sleeve or can be designed telescopically. A leaf spring, which is installed essentially horizontally and is clamped on one side, is also a possible solution as a guide element.

Exemplary embodiments of the invention are explained with reference to the attached drawings.

Show it:

1 shows a schematic longitudinal section through a mold with two sealing elements according to the invention;

Figure 2 is a schematic longitudinal section through a mold with four sealing elements according to the invention;

Figure 3: in an enlarged detail of Figure 1, a section through the sealing element according to the invention and a guide element;

FIGS. 4-6: possible embodiments for fastening a sealing element according to the invention;

Figures 7-9: Design options of a swivel joint for a guide element;

Figure 10: a plan view of an alternative embodiment of a guide element.

FIG. 1 shows a first embodiment of a mold for a continuous casting plant. The mold comprises a pouring tube 10 which forms a pouring channel 12 for the liquid steel. This pouring tube 10 comprises, for example, a one-piece copper tube 12 made of pure copper or a copper alloy, which is provided at its lower end with a lower flange 16 and at its upper end with an upper flange 18. Vertical struts 20 connect the lower flange 16 to the upper flange 18 and give the pouring tube additional rigidity. It should be noted that the pouring tube 10 can of course also comprise individual shaped plates instead of the one-piece copper tube 12. These mold plates are then held together by a frame structure to form the pouring tube. The mold can be designed to cast a wide variety of products, such as billets, pre-profiles (beam blanks), slabs, thin slabs, etc.

The pouring tube 10 is surrounded by an outer cooling box 22, which has a lower frame 24 and an upper frame 26. This cooling box 22 is carried by a stationary support structure, which is indicated in FIG. 1 by the supports 28, for example. The pouring tube 10 is in this case carried by a rocker arm 30 which is connected to the fixed cooling box 24 via a cylindrical swivel joint 32. A second cylindrical swivel joint 34 connects the pouring tube 10 to the free end of the rocker arm 30. The other end of the rocker arm 30 is connected, for example, to a hydraulic cylinder which generates vibrations with a stroke of a few millimeters and with a frequency of a few Hertz. These vibrations are applied to the pouring tube 10 via the lifting device 30.

The lower flange 16 of the pouring tube 10 is connected to the lower frame 24 of the cooling box 22 by means of a first flexible sealing element 36 according to the invention. The upper flange 18 of the pouring tube 10 is connected to the upper frame 26 of the cooling box 22 by means of a second sealing element 38 according to the invention. Urn the pouring tube 10 is accordingly axially sealed by the two sealing elements 36, 38 according to the invention, wherein the pouring tube 10 can swing freely in the cooling box 22 along the pouring axis.

The two sealing elements 36, 38 according to the invention consist of a flexible material, preferably a rubber-elastic material with fabric inserts. Each of the sealing elements 36, 38 forms an annular membrane, the outer edge of which is clamped in the upper or lower frame 26, 24 of the cooling box 22, and the inner edge of which is clamped in the upper or lower flange 18, 16 of the pouring tube 10 .

The lower membrane 36 is described on the basis of FIG. 3, representative of all other membranes. The membrane 36 forms a circumferential bulge 40, the convex side of which faces the annular pressure chamber. An essentially flat ring body 42, 44 flows smoothly on both sides of this circumferential bulge 40. The wall thickness of the membrane and the reinforcing inserts are designed so that the circumferential bulge 40 maintains its convex bulge in the direction of the pressure chamber even after pressurization of the annular pressure chamber. If the pouring tube 10 is now moved downward by an amount + y (in practice it is in most cases about 5 to 10 mm) (see arrow), the membrane 36 assumes the shape indicated by dashed lines. It is test that the deformation of the membrane consists essentially in a flattening of the bulge 40, that is, in a change in the radii of curvature. It should be noted that the material of the membrane 36, during an axial movement of the pouring tube 10, is not substantially stretched neither in the radial nor in the circumferential direction, that is to say that the stroke movements do not result in any significant tensile stresses in the membrane. Furthermore, the pressure in the annular pressure chamber acts on the convex side of the circumferential bulge 40 of the sealing element 36 and essentially generates compressive stresses in this sealing element 36. This prestressing of the sealing element 36 has a positive effect on the vibration stress of the sealing element, since it counteracts the remaining tensile stresses that arise during the oscillation process and thus reduces the tensile stress peak values in the material of the sealing element.

In FIGS. 3 and 5 it can be seen that the membrane 36 has an annular bead 24, 44 with a round cross-section both on its inner and on its outer edge. This annular bead 24, 44 is fitted and clamped in an annular groove of the flange 16 on the pouring tube or in an annular groove of the frame 24 on the cooling box 22 by means of a fastening flange 16 ″ or 24 ″. In FIG. 4, the annular bead 44 ″ has essentially a rectangular cross section with two concave, circumferential indentations in which a bead of the frame 24 or the fastening flange 24 ″ engages. The reference number 48 shows a through hole for a bolt in the bead 44 '. If the annular bead 44 ″ in FIG. 4 is designed to be relatively flat, the annular bead 44 ″ in FIG. 6 has a greater height than width.

As shown in FIG. 3, the membrane 36 is advantageously spanned with at least one guide element 50. This guide element 50 transmits horizontal forces, which are exerted by the strand on the pouring tube 10, from the pouring tube 10 via the lower frame 24 to the supporting structure 28 (see FIG. 1). In FIG. 3, the guide element 50 is connected to the flange 16 or the frame 24 by means of cylindrical or spherical joints 51 or 52. As can be seen more clearly from FIG. 7, the joint 52 not only allows the guide element 50 to be rotated about the joint axis “O” but also to move the guide element 50 to the right by the amount “x”, where: X> L - (l_2 - ymax2) 0 · 5, L = length of the guide element 50, ymax = maximum stroke (positive or negative).

As a result, the guide element 50 does not provide any substantial resistance to the vertical stroke movements of the pouring tube 10. In other

Words, the lifting movements of the pouring tube 10 cause neither tensile stresses nor bending stresses in the guide element 50. When horizontal forces are transferred from the pouring tube to the frame 24, the guide element 50 works exclusively in the direction of the arrow 44 and is under compressive stress. The guide element 50 in FIG. 3 thus prevents the pouring tube 10 from moving in the direction of the arrow 54. A second guide element 56 (see FIG. 1), which is arranged on the opposite side of the pouring tube 10, prevents the pouring tube 10 from moving in the opposite direction of the arrow 54. Further guide elements can, for example, be arranged in a plane perpendicular to the drawing.

The design of the joint in FIG. 8 corresponds to the design of the joint in FIG. 7, only one sliding sleeve 58 being provided for the cylindrical articulation pin 60 of the guide element 50. FIG. 9 relates to an alternative embodiment of the joint of a guide element 50. In this embodiment, two lateral bearing journals 60 are each equipped with an elastically compressible sleeve 62, for example made of rubber, and are each fitted into a bearing bore in a fastening tab 64. The elastically compressible sleeve 62 ensures that the guide element 50 ’does not oppose any substantial resistance to the vertical stroke movements of the pouring tube 10. In contrast to the guide elements 50 of FIGS. 7 and 8, the guide element 50 ′ of FIG. 9 can transmit both compressive stresses and tensile stresses. The guide element 50 can also be designed as a spring element (for example as a leaf spring). One end of the spring element is to be clamped rigidly and the second end is to be mounted in a joint corresponding to FIG. 7, 8 or 9. In this embodiment, the lifting movements of the pouring tube 10 in the spring element cause bending stresses, but no tensile stresses. The guide elements 50 can also be designed as a telescopic rod, with blocking means limiting the axial collapse of the telescopic rod. Although good guidance by the lifting device 30 is ensured at the upper end of the mold, guide elements can of course also be arranged between the upper flange 18 and the upper frame 26.

In Figure 10, an additional design of a guide element is shown. This guide element 50 ”is designed as a metallic, spring-elastic ring membrane with radial, wedge-shaped openings 150. In other words, the guide element 50 ”has an outer ring flange 152 and an inner ring flange 154, which are connected to one another via resilient webs 156. The outer ring flange 152 is clamped in the frame 24. The inner ring flange 154 is clamped in the flange 16 of the pouring tube 10.

In FIG. 1, the reference number 70 designates a sealing device which divides the annular chamber between the pouring tube 10 and the cooling box 22 into an upper collector 72 and a lower collector 74, while allowing the pouring tube 10 to move freely in the cooling box 22. This sealing device 70 advantageously comprises an inner ring plate 76 on the pouring tube 10 and an outer ring plate 78 on the cooling box 22, which are connected by means of an annular, flexible sealing membrane 80. This annular, flexible sealing membrane 80 advantageously has a circumferential bulge which is designed such that its convex side faces the collector in which the pressure is highest (in FIG. 1 this is the lower collector 74). The lower collector 74 is supplied with cooling water via an inlet line 82. This cooling water flows through an annular inlet slot 84 into an annular gap 86, which is formed around the pipe 14 by a water-conducting jacket 88. The cooling water flows into the upper collector 46 via an annular return slot 90 and finally leaves the mold via a return line 92.

Ring lines 116, 118 with spray nozzles are arranged on the outside below or above the ring membranes 36, 38. The latter spray the side of the ring membranes 36, 38 facing away from the pressure chamber with a cooling liquid. This results in a relatively uniform cooling of both

Reached outside and inside of the relatively thick and poorly conductive ring membranes 36, 38, which prevents premature aging of the ring membrane branches.

FIG. 2 shows an embodiment of a mold for a continuous casting installation with four ring membranes 100, 102, 104 and 106 according to the invention. This embodiment differs from the embodiment of FIG. 1 essentially in that the upper and lower collector 72, 74 of the figure 1 are formed as flexible ring collectors 72 ', 74' by two ring membranes 100, 102 and 104, 106, one above the other. These ring membranes 100, 102 and 104, 106 are designed and fastened as described above.

The actual cooling box 22 is therefore omitted in the mold according to FIG. 2. The pouring tube 10 is only surrounded by a supporting structure 108 in which the pouring tube 10 is suspended and the two pairs of ring plates 110, 112 and 114, 116 for connecting the ring membranes 100, 102 and 104, 106. The ring plates of each pair 110, 112 and 114, 116 are each connected to one another via an outer pressure jacket 111, or 115. Ring plate pair 110, 112 and pressure jacket 111 form an outer fixed boundary of the lower ring collector 74 '. Ring plate pair 114, 116 and pressure jacket 115 form an outer fixed boundary of the upper ring collector 72 '. Support brackets 118 connect the outer fixed boundary of the upper ring collector 72 'with that of the lower ring collector 72' and create axial space between the ring collectors 72 ', 74' for an electromagnetic stirrer 200. It should be noted that between the ring collectors 72 ', 74 'The water jacket 88' is of course designed as a pressure jacket, since he has to endure the cooling water pressure here. As in FIG. 1, the ring membranes 100 and 106 are also spanned with guide elements, and ring lines 120, 122, 124 and 126 are arranged with spray nozzles above and below the ring membranes 100, 102, 104 and 106.

Claims (21)

1. Sealing element made of flexible material for sealing an annular gap between a vibrating pouring tube (10) and a stationary housing component (22) of a continuous casting mold, characterized by a circumferential bulge (40) which is designed such that its convex side when the sealing element (36 , 38, 80, 100, 102, 104, 106) is arranged on the pressure side. 2. Sealing element according to claim 1, characterized in that the sealing element is designed as an annular membrane. 3. Sealing element according to claim 1, characterized in that the sealing element is designed as a pipe socket. 4. Sealing element according to one of claims 1 to 3, characterized in that the sealing element is made essentially of a rubber-elastic material. 5. Continuous casting mold with a vibrating pouring tube (10), a fixed housing (22) and at least one flexible sealing element for sealing an annular pressure chamber for a cooling liquid between the vibrating pouring tube and the fixed housing, characterized in that the flexible sealing element (36, 38, 80, 100, 102, 104, 106) falls under one of claims 1 to 4 and the convex side of its circumferential bulge (40) faces the annular pressure chamber. 6. Continuous casting mold according to claim 5, characterized by a vibrating device and a supporting structure (22), the supporting structure carrying the vibrating device and the vibrating device carrying the pouring tube. 7. continuous casting mold according to claim 6, characterized in that the oscillating device comprises a rocker arm (30) which is articulated in the support structure (22) and is articulated to the pouring tube (10). 8. Continuous casting mold according to one of claims 5 to 7, characterized in that the lower and upper end of the pouring tube with the fixed housing (22) each have a flexible sealing element (36, 38) according to one of claims 1 to 4 is connected in such a way that an annular pressure chamber (72, 74) for a cooling liquid is delimited around the pouring tube (10). 9. Continuous casting mold according to claim 8, characterized in that the annular chamber is divided by an inner sealing device (70) into a lower and upper annular collector (72 and 74), these lower and upper annular collectors (72 and 74) having a Inlet line (82), or a return line (92) for a coolant are connected. 10. Continuous casting mold according to claim 9, characterized in that the inner sealing device (70) comprises an elastic ring membrane (80). 11. Continuous casting mold according to claim 9 or 10, characterized in that around the pouring tube (10) a water guiding jacket (88) is arranged such that it forms an annular gap along the pouring tube which on the one hand opens into the lower collector and on the other hand into the upper collector. 12. Continuous casting mold according to one of claims 5 to 7, characterized by a lower and upper flexible ring collector (72 ', 74') which surrounds the lower or upper end of the pouring tube (10), these flexible ring collectors (72 ', 74 ') each comprise two directly opposite flexible sealing elements (100,102), (104,106) according to one of claims 1 to 4, which are arranged such that they delimit an annular pressure chamber for a cooling liquid between them. 13. Continuous casting mold according to claim 12, characterized in that a water guiding jacket (88 ') is arranged around the pouring tube such that it forms an annular gap (86') along the pouring tube (10) which, on the one hand, into the lower flexible ring collector (74 ') and, on the other hand, opens into the upper flexible ring collector (72 '), this water guiding jacket (88') being designed as a pressure jacket outside the ring collectors (72 ', 74'). 14. Continuous casting mold according to claim 12, characterized in that an electromagnetic stirring device (200) is arranged between the lower and upper flexible ring collector (72 ’, 74’). 15. Continuous casting mold according to one of claims 5 to 13, characterized in that a cooling water spray device on the side facing away from the pressure chamber of the at least one flexible sealing element is arranged such that this side of the flexible sealing element can be sprayed with cooling water. 16. Continuous casting mold according to one of claims 5 to 14, characterized by at least one guide element which is arranged between the vibrating pouring tube and the fixed housing such that it limits a lateral pivoting out of the pouring tube in at least a first direction. 17. Continuous casting mold according to claim 15, characterized in that the guide element is connected via at least one swivel joint to the oscillating pouring tube or the fixed housing. 18. Continuous casting mold according to claim 16, characterized in that the guide element has a horizontal play in at least one swivel joint which permits horizontal displacement of the guide element in a second direction, which is opposite to the first direction. 19. Continuous casting mold according to claim 16, characterized in that the guide element is mounted in at least one swivel joint in an elastically compressible sleeve. 20. Continuous casting mold according to claim 15 or 16, characterized in that the guide element is telescopic. 21. Continuous casting mold according to claim 15, 16 or 17, characterized in that the guide element is designed as a leaf spring which is installed essentially horizontally.