Abstract:
The invention relates to a strip-casting machine ( 20 ) for producing a metal strip. Said strip-casting machine consists of a pair of casting rolls ( 22, 24 ) arranged in side-by-side parallel relation with a casting gap thereinbetween and of lateral sealing elements ( 25 ) that are provided with respective sealing plates ( 61 ) at both sides of the casting rolls ( 22, 24 ) that are pushed or pressed against the casting rolls from the front by means of pushing or pressing means. The respective sealing plate ( 61 ) is pushed or pressed against the two equilateral front faces ( 22′, 24 ′) of the casting rolls ( 22, 24 ) in such a manner that, in the heated operational state, it facilitates an extremely exact positioning on the front faces of the casting rolls. To this end, the sealing plate ( 61 ) is mounted in such a manner as to allow a three-dimensional displacement of the sealing plate, as if floating.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to strip-casting machine for producing a metal strip with two casting rolls set up next to each other to form a casting gap and with lateral sealing elements, each of which comprises a sealing plate which can be pressed against the end surfaces of the casting rolls on one side, where the sealing plate in question can be pressed against the two end surfaces of the casting roll in such a way that very precise contact can be achieved between the plate and the end surfaces of the casting rolls at the high temperatures of the casting operation. 
     2. Description of the Related Art 
     In a strip-casting machine of the general type in question according to EP-A 0,714,716, the device for sealing off the sides of the casting rolls consists of refractory sealing plates, one of which is pressed against the end surfaces of the two casting rolls on each side; these sealing plates prevent the molten steel poured in between the casting rolls from escaping toward the side. A metal bath is formed instead, as in a conventional mold. As these sealing plates are pressed against the rotating casting rolls, they are subjected to wear, which is accompanied by the large thermal load caused by the metal bath. The sealing plates are connected to a pressing device, which is designed in such a way that a disadvantageous wear pattern is necessarily formed on the sealing plates. One of the main problems of strip-casting machines of this type therefore remains unsolved, namely, the problem of ensuring that the lateral sealing elements offers a reliable seal throughout the entire duration of the casting operation. 
     In the case of casting rolls with small diameters in the range of approximately 500-800 mm, the seals to be provided for the roll sides are proportionately smaller. Because of the small volume of the metal bath, however, the surface of the molten bath is unsteady. In the case of large casting rolls with diameters of, for example, approximately 1,500 mm, the surface of the molten bath is calmer because of its larger volume. Although this is advantageous, larger and more complicated lateral sealing elements become necessary. As a result of manufacturing and installation tolerances, irregular wear, and differences in the degrees to which casting rolls are heated as a result of deposits, it is possible that the sealing edges or sealing surfaces of the rolls are not precisely aligned with each other. 
     From Japanese Patent Early Disclosure JP 4 [1992]-224,052 A, a strip-casting machine with two casting rolls is known, in which the frictional forces between a sealing plate and the end surfaces of the casting rolls are measured, and the pressing forces acting on the sealing plates are modified accordingly. This goal is to reduce asymmetrical wear on the sealing plate and to avoid the danger of the leakage of molten metal. The pressing forces are transmitted to the sealing plate by three hydraulic cylinders. The sealing plate is guided rigidly in an axial direction in a guide sleeve, which is disadvantageous. 
     In the document EP 0,806,997, a twin-roll casting system is described. The sealing plate for the two casting rolls consists of an upper and a lower part. The lower part of the sealing plate is pressed with much higher pressure against the end surfaces of the two casting rolls where they form the edges of the triangular gap than the upper part is. The upper sealing plate part is pressed by three cylinders against the rolls. The pressure applied by the cylinders is distributed uniformly over all the cylinders. The wear pattern of the sealing plate is necessarily irregular, even when a so-called “spring return” for the individual pressure cylinders is provided as a restoring force. The danger of leakage as a result of premature wear of the sealing plates remains high. 
     The document EP 0,692,330 B1 deals with the casting of strip between two casting rolls, the end surfaces of which are sealed off by sealing walls. For the continuous determination of the state of the contact between the end surfaces of the rolls and the sealing walls, the frictional conditions are measured and compared with specified settings. At least one casting parameter is controlled on the basis of the results of the comparison. The position of the sealing wall can also be controlled on the basis of the value of the friction conditions. For this purpose, the sealing wall is held by an arrangement which consists of a main slide, which can slide in the direction of the rolls, and a secondary slide, which is guided horizontally on the main slide. Thus the sealing wall can be adjusted in two planes in order to measure the pressure or the forces on the sealing wall in the vertical and horizontal directions. The measurement setup does not, however, eliminate the danger of leaks at the sealing walls as a result of irregular wear. 
     A twin-roll continuous casting machine with side walls pressed against the rolls for the continuous casting of thin metal strips is also described in another document, namely, EP 0,698,433 B1. The side walls are connected to a pressure plate and a support plate, so that the side walls can be moved in the axial direction of the casting rolls and also perpendicular to that direction. Between the pressure plate and the support plate, several compression springs are inserted, which act on the side walls. Each side wall is surrounded by a cooled ring. The pressure plate is carried by a cart, which can move in the axial direction. On the cart there is an adjusting cylinder, which acts on the pressure plate. The previously known design, however, is unable permanently to prevent irregular wear of the side walls and thus unable to guarantee the required absence of leakage between the casting rolls and the side walls over the course of several casting sequences. 
     SUMMARY OF THE INVENTION 
     Against this background, the present invention was based on the task of improving a strip-casting machine of the general type indicated above in such away that the required absence of leakage at the lateral sealing elements is ensured during the entire casting operation, even when casting rolls of optimum diameter are used. Another goal is that it should be possible with the improved machine to deliver the lateral sealing elements quickly and after replacement has been completed to carry out operations reliably with them. 
     The task is accomplished according to the invention in that each sealing plate is supported in a floating manner so that it can be set or pressed against the rolls with freedom to move in three dimensions. As a result, very precise contact can be achieved between the sealing plate and the end surfaces of the casting rolls even at the high temperatures of the casting operation, and the wear of the sealing plate is reduced to a minimum. 
     In a highly advantageous embodiment, each lateral sealing element is attached to a carrier element. This carrier element consists of the sealing plate, a support frame holding the sealing plate, the setting or pressing means acting on the frame, and the floating support of these components on the carrier element. 
     In a further elaboration of the invention, it is provided that at least one of the casting rolls can be adjusted, especially in the axial direction, so that the end surfaces of the rolls can be aligned with each other on a plane as accurately as possible and/or aligned with respect to the sealing plates. 
     With this strip-casting machine according to the invention, optimum lateral sealing of the casting rolls is achieved, the functionality of the seals remaining effective for the entire duration of the casting operation even in the case of casting rolls with diameters of more than 1 meter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     An exemplary embodiment of the invention and additional advantages of same are explained in greater detail below on the basis of the drawing: 
     FIG. 1 shows a section through a strip-casting machine with the lateral sealing elements according to the invention; 
     FIG. 2 shows a longitudinal section through a lateral sealing element according to FIG. 1; 
     FIG. 3 shows a section through the lateral sealing element along line III—III of FIG. 2; 
     FIG. 4 shows a device for the axial displacement of the cylindrical, cooled jacket of a casting roll on its stationary axle; and 
     FIG. 5 shows a device for the axial displacement of the stationary axle of a casting roll with a cylindrical jacket which rotates around the axle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a strip-casting machine  20  for producing a metal strip  15 , especially a steel strip, which can be produced by a continuous casting operation. This strip-casting machine  20  stands on a suggested steel structure  12  and is supplied with molten metal by a tundish vessel mounted above it, as known from conventional continuous casting systems. It is advisable for the tundish vessel to have a stopper or the like to close the discharge opening, through which the molten metal can flow. 
     The strip-casting machine  20  consists primarily of two casting rolls  22 ,  24 , set up essentially parallel to each other with rotational axes approximately on a horizontal plane. Lateral sealing elements  25  can be pressed against the two end surfaces of the rolls on each side, as a result of which an enclosed space is created with a casting gap open at the bottom. The casting rolls  22 ,  24  are supported on both sides on a standard  32 , and each is driven in a controlled manner by an motor. The strip-casting machine  20  standing on a suggested steel structure  12  or the like is enclosed by a housing  30 , so that the strip-casting operation can be carried out under an inert gas, sealed off from the air. On top of the housing  30  are sliding doors  35 , so that the housing can be opened and closed. 
     Each of these lateral sealing elements  25  has a sealing plate  61 , which can be pressed by a pressing device against the end surfaces of the casting rolls  22 ,  24  to form a mechanical seal. These triangular sealing plates  61 , made of a refractory material, cover approximately the upper part of the end surfaces  22 ′,  24 ′ of the casting rolls. 
     According to the invention, each of the sealing plates  61  can be pressed against the two end surfaces  22 ′,  24 ′ on one side in such a way that very precise contact can be achieved between the plate and the end surfaces of the casting rolls even at the high temperatures of the casting operation. 
     According to FIGS. 2 and 3, each sealing plate  61  is for this purpose arranged so that it can be moved by the pressing means against the end surfaces  22 ′,  24 ′ of the casting rolls. Each plate is also supported in a floating manner via an articulation means, in the present case a ball joint  81 , so that a constant pressure can be applied and so that the sealing surfaces  61 ′ can be kept precisely parallel to the two end surfaces of the casting rolls, which lie on the same plane. 
     The pressing means has at least one and preferably three pressure cylinders  71 , each cylinder having a piston  72 , which can be displaced in a direction approximately perpendicular to the sealing plate  61 . By way of a support frame  64 ,  65 , the pressure cylinders exert a nearly constant, controllable pressure on the associated sealing plate  61  in the manner of a three-point bearing; these pressure cylinders  71  advisably act on the corner areas of the sealing plate  61 , which, because of the arrangement of the casting rolls, is approximately triangular. 
     The support frame  64 ,  65  carrying the sealing plate  61  is connected by articulated joints  66 ,  67  to a butt plate  80 , which is supported on the carrier element  41 ,  41 ′ in a floating manner by the ball joint  81 ; the support frame  64 ,  65  is pressed continuously against the pistons  72  of the pressing means by an elastic connection, namely, an adjustable tension spring  68  with anchor, located between the frame and the butt plate  80 . The articulated joints consist in each case of an approximately horizontal articulated lever  66  and an vertical articulated lever  67 , these articulated levers  66 ,  67  also being spherically supported on the support frame  64  at one end and on the butt plate  80  at the other end, so that the sealing plate  61  can be moved parallel to the butt plate  80  in three different directions. With optimum support of the sealing plate  61 , it is possible to exclude permanently the possibility that the plate could become jammed or locked even when the entire lateral sealing element is at elevated temperature. 
     A projecting centering pin  82 , furthermore, is provided on the ball joint  81 , by means of which the carrier element  41  can be centered with respect to the device  85 . A cam  83  or the like makes it possible to center the lateral sealing element  25  vertically with respect to the carrier element  41 . A flexible retaining element  84  is provided between the butt plate  80  and the top part  41 ′ of the carrier element  41 . A stop screw  86  on this top part  41 ′ limits the range over which the plate  80  can swing. 
     FIG. 1 also clearly shows that the carrier element  41  holding the lateral sealing elements  25  is associated with a manipulator  40 , by means of which the lateral sealing element in question can be moved laterally away from the casting rolls  22 ,  24  and returned. After the lateral sealing elements  25  have been brought laterally up into position next to the casting rolls  22 ,  24 , they are centered by a device  85  mounted on the standard  32  for the casting rolls, and the cylinders  71  are connected to their respective drive elements. Conversely, after the device  85  has been disconnected, the lateral sealing elements  25  can be moved away by the manipulator for maintenance. The device  85  is mounted on the standard  32 , but it could also be mounted on the manipulator. 
     A monitoring and control system for these lateral sealing elements  25  makes it possible to adjust the pressing means acting on the sealing plate  61  in optimum fashion and also to monitor the system for problems, leaks, etc., both for the sake of prevention and for the sake of early detection in conjunction with an on-line error correction system, especially in regard to the sealing plate. 
     FIG. 4 shows a device for the axial displacement of the end surfaces  22 ′ of the casting rolls  22  to be sealed and for their alignment with respect to each other. The casting roll  22  consists of a stationary axle  1  with an axle journal  2 , which is supported on a stand  3 . The casting roll  22  comprises a ring-shaped support element  4 , which is connected to the cylindrical jacket  5  by means of a wedge-type clamping device  6 . The jacket  5  is provided around its circumference with axially oriented cooling bores  7 , which are connected to additional bores  9 ,  10 ,  11  in the support element  4 , in the axle  1 , and in the stand  3 , which supply and carry away a coolant. The jacket  5  and the support element  4  are mounted rotatably on the axle  1  by the bearings  8  and are driven by a motor/transmission device (not shown). So that the end surfaces  22 ′ of the casting roll  22  can be aligned on the same plane with the end surfaces of the other casting roll (not shown), the jacket  5  is mounted on the stationary axle  1  with freedom to shift position together with the support element  4 . The displacement is accomplished with a ring-shaped, double-acting piston-cylinder unit  13 , which is connected to both the support element  4  and the axle  1  and is installed at the end of the casting roll  22 . A piston ring  14  on the support element  4  engages with clearance in a circumferential groove  16  in the axle  1 , so that cylindrical chambers  17  are formed at the sides of the piston ring  14 . Pressure can be built up in either of these chambers by a pressure medium via pressure lines p 1  and p 2 . As a result of the pressure difference ±p between the chambers, the support element  4  and thus the end surface  22 ′ of the casting roll  22  are shifted by a maximum value of, for example, 8 mm toward one side or the other. It is also possible for a second displacement device or pressure device to be set up at the other end of the casting roll. 
     An alternative design of a displacement device  13  is shown in FIG.  5 . The cylindrical, cooled jacket  5  with its cooling bores  7  is shown on the stationary roll axle  1 . The jacket  5  is supported by support elements  4  on the axle  1 . One of the support elements  4 ′ is connected to the jacket  5  and is, for example, held with freedom of rotation on the axle  1  by means of a radial bearing  18 . The other support element  4 ″ is connected to the axle  1 , where the cylindrical jacket  5  is supported with freedom of rotation on the support element  4 ″ by means of an axial bearing  19 . Between the support elements  4 ′ and  4 ″, there is an electromagnetic brake  21  on the axle  1 . So that the end surfaces  22 ′ of the casting roll  22  can be brought into alignment on the same plane with the end surfaces  22 ′ of the other casting roll (not shown), the axle  1  is shifted together with the cylinder  5  in the axial direction. For this purpose, and adjusting device  26 , designed, for example, as a piston-cylinder unit  27  with a restoring spring  28 , acts on the one side of the axle  1 . On the other side of the axle  1 , there is a pressure device  29