Abstract:
The invention relates to a strip-casting machine ( 20 ) for producing a metal strip ( 15 ). Said strip-casting machine comprises a pair of casting rolls ( 22, 24 ) which are arranged adjacent to each other, form a casting gap and are rotatably mounted on a machine tool table ( 32 ). The casting rolls ( 22, 24 ) and at least the machine tool table ( 32 ) carrying said rolls can be displaced on rails ( 48, 48′ ) or the like from the casting position (G) into a waiting position (W) and vice versa. The machine tool table ( 32 ) together with the casting rolls ( 22, 24 ) can thereby be displaced away from the casting position (G) by such a distance that a second machine tool table ( 32 ) that is provided with prepared casting rolls ( 22, 24 ) can be displaced into the casting position (G). The machine tool table ( 32 ) is held in a displaceable manner and preferably together with a housing ( 30 ) which surrounds said table. The inventive strip-casting machine allows for quick maintenance or quick changing of the casting rolls and an increase in the casting performance thereof.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to a strip-casting machine for producing a metal strip with two rotatably supported casting rolls set up next to each other to form a casting gap, where the casting rolls can be shifted away from the casting position to a servicing position and back again, and to a method for controlling the strip-casting machine. 
     2. Description of the Related Art 
     In strip-casting machines with two casting rolls, arranged essentially parallel to each other, side pieces are used to form the boundaries of the casting gap on the narrow sides. When strips, especially steel strips are cast, these side pieces are worn down by abrasive wear as a result of the friction with the casting rolls and also, in the lower part, by the friction with the solidified strip. When thus worn out, these side pieces must be replaced. So that they can be replaced, the side pieces are moved out of the casting position, in which they rest against the barrels, by means of the setting device in an essentially horizontal direction away from the barrels and into a setting position. Then side piece changing devices, e.g., robots, which are mounted on the casting platform on both sides of the machine, raise the side pieces up and out of the setting position. Japanese Patent Kokai JP-5[1993]-329,583 A, for example, describes robots of this type for replacing these side pieces. 
     In the known strip-casting machines, the casting rolls are stationary and are mounted rigidly underneath a ladle turret and a tundish vessel or the like. When these casting rolls must be serviced by regrinding or when they must be replaced, for example, a great deal of complicated disassembly and reassembly work is involved, because the casting rolls are difficult to access in themselves. Because of their weight, furthermore, they must be lifted away by a crane and set back into position again with an accuracy on the scale of millimeters. The connection and disconnection of the water lines or the electrical connecting lines is also associated with cumbersome work procedures because of the limited degree of accessibility present. It is even necessary to divide the structural frame on which the casting rolls are supported into two parts. 
     Another disadvantage of these known strip-casting machines is that, during the maintenance or servicing of the casting rolls or of the machine, no casting work can be done, which limits the casting output of the installation. 
     In a strip-casting machine of the general type in question according to WO-A 93/22,087, the casting rolls are supported on a cart, which can be moved along rails by a cylinder over a distance equal to approximately half the length of the cart. This design of the strip-casting machine, however, is suitable only for casting rolls of small diameter. The accessibility to the casting rolls in the servicing position a certain distance away from the casting position, furthermore, is still only slightly improved, because the rolls are still relatively close to the casting position. 
     SUMMARY OF THE INVENTION 
     The present invention was based on the task of creating a strip-casting machine of the general type described above in which optimum accessibility to the machine and especially to the casting rolls is made possible, as a result of which the rolls can be serviced or replaced rapidly, and in which the availability of the strip-casting machine for casting and thus the casting output of the installation can be increased. 
     The task is accomplished according to the invention in that the casting rolls can be shifted away from the casting position by a distance such that a second, prepared pair of casting rolls can be moved into the casting position. 
     With this design of the strip-casting machine according to the invention, in which the casting rolls can be shifted into a servicing position some distance away from the casting position and immediately replaced by another prepared set of casting rolls, considerable advantages are obtained in comparison with the known systems. 
     In an elaboration of the invention, it is provided that the casting rolls are supported rotatably on a structural frame; that the structural frame can be shifted away from the casting position by the distance indicated above; and that a second structural frame provided with prepared casting rolls can be shifted into the casting position. 
     By shifting the structural frame with the casting rolls to a servicing position, tools, gauges, finishing equipment, measurement and other control devices, etc., can be set up permanently at this location. This allows the machine to be maintained and serviced both quickly and also professionally. After a structural frame has been moved away to allow, for example, the casting rolls to be replaced with others of a different width or in cases where the casting rolls are no longer functional, newly prepared casting rolls on a different structural frame can be brought immediately into position underneath the tundish vessel, so that casting can begin again or continue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Exemplary embodiments of the invention and additional advantages of same are explained in greater detail below on the basis of the drawings: 
         FIG. 1  is a schematic longitudinal section through a strip-casting machine according to the invention with a front view of the structural frame and of the casting rolls mounted on it; 
         FIG. 2  is a section through the strip-casting machine according to  FIG. 1 ; 
         FIG. 3  is a section through the casting machine with illustration of the servicing positions of the casting rolls; 
         FIG. 4  id a schematic top view of the casting machine; and 
         FIG. 5  is a schematic top view of a variant in the form of a twin-strand casting machine. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a strip-casting machine  20  of a casting installation  10  for metal strip  15 , especially a steel strip, which can be produced in a continuous casting operation. This strip-casting machine  20  is supported on a carrier system  12  and is supplied with molten metal from a tundish vessel (not shown), located above it, as known from conventional strip-casting systems. 
     This strip-casting machine  20  consists primarily of two casting rolls  22 ,  24 , essentially parallel to each other, the axes of which are approximately horizontal, and which are provided at each end with a lateral sealing element  25 , as a result of which an enclosed space is created with a casting gap open at the bottom. The casting rolls  22 ,  24  are rotatably supported at each end on a structural frame  32 , and each is driven in a controlled manner by its own motor. One of the parts  32 ′ of the structural frame  32 ,  32 ′ and the casting roll  22  belonging to it can be swung around an axis  71  by an adjusting means  72  for the purpose of adjusting the width of the casting gap. 
     Each of the casting rolls  22 ,  24  consists of a motor-driven cylindrical jacket and a stationary axle  75 , on which the jacket is rotatably supported. Each of the axles  75  is supported at each end in the structural frame  32 ,  32 ′. This design with stationary axles  75  makes it possible to assemble the structural frame and the axles easily together into a unit. 
     The casting rolls  22 ,  24  in the structural frame  32  and the lateral sealing elements  25  are surrounded on all sides by a sealable housing  30 . During the casting operation, the interior  33  of the housing is kept filled with a shielding gas, preferably an inert gas. It is highly advantageous for this box-shaped housing  30  to leave a certain gap between it and the casting rolls  22 ,  24  and the structural frame  32  both at the sides and also at the top. 
     A cover  35 , which rests approximately horizontally on top of the housing  30 , is provided; this cover can be shifted from the closed position shown to a raised position  35 ′ and shifted horizontally away from this raised position to a position  35 ″. For this purpose, the cover has rollers  27  on the sides, which travel along suitable rails  28 . In the closed position shown, the cover  35  is advantageously lowered to the bottom level  14  to produce the desired seal of the housing  30 . 
     The housing  30  also has openings  39 , which can also be closed by doors  36 ; these openings are provided so that manipulators  40 , which can travel outside the housing  30 , can carry each of the lateral sealing elements  25  of the casting rolls  22 ,  24  away from the operating position shown, through the openings  39 , and out of the housing  30  and back again. Each manipulator  40  has for this purpose a supporting arm  41 , to which the lateral sealing element  25  is attached. The sealing element can thus be moved by the manipulator  40  from the operating position to a remote servicing position  25 ′ and back again. In the operating position of the manipulator  40 , it is possible to use a separate protective enclosure  38  to seal off the unsealed opening  39 . This protective enclosure  38  surrounds the manipulator  40  and is pressed tight against the side of the housing  30 . Also indicated are holders  88  for delivering and taking away the lateral sealing elements  25 . It is advantageous to install two such manipulators  40  on each side of the housing  30  so that they can alternate in delivering the corresponding lateral sealing elements  25  to the end surfaces of the casting rolls  22 ,  24 , after which they press the seals against the casting rolls with precise positioning during the casting operation. 
     Underneath the housing  30 , the cast metal strip  15  is guided through an additional longitudinal housing  44 , which forms a chamber  45 , in which a shielding gas is also present to prevent the metal strip  15  from coming in contact with oxygen and thus especially to prevent scale formation. In this chamber  45 , several rollers  46  and press rolls  47  are provided to guide the metal strip  15  through the longitudinal housing  44  and through a sealed opening  58  at one end. After it emerges from the housing  44 , the metal strip can be, for example, rolled, cooled, coiled, or processed in some other way. 
     Underneath the opening  30 ″, i.e., underneath the casting gap, furthermore, the longitudinal housing  44  has a pit  49  set into the installation floor  61 , where a collecting tank  52  is provided. This collecting tank  52  has the job of preventing damage by catching the molten metal which can escape from between the casting rolls in the event of a leak. Above this tank  52  are pivoting clack valves  54 ,  55 , which, in the position shown, leave an opening. When pivoted into the positions shown in dash-dot line, the flaps  54 ′,  55 ′ serve as a guide path for the metal strip  15 . 
     The housing  30  has a feed line (not shown) for the injection of shielding gas into the interior  33 ; the gas can be sent around a circuit and cooled before being returned. Upon completion of the casting operation but before the housing is opened, the shielding gas can be drawn off into a storage tank, and the air in it can be filtered out if desired. 
     According to the invention, the casting rolls  22 ,  24  and at least the structural frame  32  supporting them are supported on rails  48  or the like so that they can be shifted from the casting position G shown to a servicing position W and back again. In the present exemplary embodiment, furthermore, the box-like housing  30  surrounding the structural frame  32  is also movable, for which purpose it has wheels  37 , guided externally on the rails  48 ,  48 ′. 
     As can be seen in  FIG. 2  also, the rails  48 ,  48 ′, which form a pair and carry the housing  30 , have a section in the area of the casting position G which is separate from the rest of the length of the rails. This section is designed so that its height can be adjusted by lifting cylinders  51  or the like, which are attached to a structure  62 . In  FIG. 1 , this section of the rails is shown in the lowered position together with the housing  30 , whereas in  FIG. 2  it is shown in the position in which it is aligned with the adjacent section of  48 ′ of the rails. In the lowered position, the water feed lines  64  leading to the casting rolls  22 ,  24  are connected to the water supply system  65 , which is provided in the housing floor. The water feed lines  64  are in the structural frame  32 , whereas the water supply system  65  along with the appropriate feed and discharge lines extends underneath the housing  30 . Thus the water lines  64  are connected and disconnected automatically upon actuation of the lifting cylinders  51 . By means of nonreturn valves (not shown), the cooling water can be prevented from escaping when the lines are disconnected. 
     The lower contact surface of the cover  35  is underneath the floor  14  when the cover is in the lowered position, i.e., in the position where it seals off the housing, so that the housing can be shifted horizontally underneath the floor  14 . As shown in  FIG. 2 , the cover is supported by its rollers  27  on the rails  28  as it is being moved and can be raised and lowered independently of the housing by lifting cylinders  74 . 
     When the housing  30  is to be replaced, a new one with prepared casting rolls  30  is pushed into the casting position G and lowered. Then the lateral sealing elements  25  are pressed by the manipulators  40  against the end surfaces of the casting rolls  22 ,  24  with a defined pressure; the protective enclosures  38  and the cover  35  are connected tightly to the housing  30 ; and the interior of the housing is inertized by the shielding gas. 
     An additional advantage of the invention is that this replacement of the casting rolls  22 ,  24  can be carried out “on the fly”, as it were; that is, the casting pipe, which passes through the cover  35  and projects between the casting rolls  22 ,  24 , can be kept in position without the need to raise the tundish vessel  18  which holds it. During a replacement operation, the cover  35  is raised; the lateral sealing elements  25  are removed; and the casting rolls  22 ,  24  are rolled away from the housing  30  horizontally in the direction of their rotational axes. In a corresponding manner, the new casting rolls or casting rolls of a different width, for example, are brought up in such a way that the casting pipe assumes a position between them again but without actually contacting them. Thus casting can continue without the need to empty the tundish vessel  18 . The only step which must be taken before casting can start again is to open the element which seals the outlet of the vessel. As a result, the output of the strip-casting machine according to the invention can be increased significantly. 
     According to  FIG. 3 , the housing  30  is designed within the scope of the invention so that it can be moved along with the used casting rolls  22 ,  24  far enough away from the casting position G that a second housing  30 ′ with prepared casting rolls can be conveyed into the casting position G. After reaching the casting position G, this housing  30 ′ can be made ready for casting by lowering the rails  48  and thus connecting the lines  64  to the water supply system  65  and by closing the cover  35 . It is advantageous for the distance between the casting position G and the servicing position W to be equal to several lengths of the housing or of the casting rolls, so that work can be carried out in the servicing position without interference from the casting operation. The exact distance depends on the circumstances of the individual casting installation. 
       FIG. 4  shows a casting installation  10  which works with a single strand. A ladle turret  81  conventional in and of itself holds a ladle  82 , from which the molten steel is poured into a tundish vessel  18 . The molten steel then passes between the casting rolls located in the casting position G. The metal strip emerging at the bottom from between the two casting rolls is then conducted away in the direction of the arrow  83 . In the servicing position W, the casting rolls  22 ,  24  are serviced by, for example, turning or grinding the surface or by some other type of surface treatment or are possibly replaced by new casting rolls as suggested in the figure. These casting rolls  22 ,  24  are pushed away together with their housing  30  along the rails  48 ′. The tundish vessels  18 ,  18 ′ are also prepared for use. These could also be pivoted into the casting position by the ladle turret. 
       FIG. 5  shows a casting installation  80  with two strands, one next to the other, where, in contrast to the installation according to  FIG. 4 , two ladle turrets  81 , each with its own servicing position W, are provided. In addition, two housings  30  with casting rolls  22 ,  24  are stationed between the casting positions G of the two strands; this location can also serve advantageously as a servicing position. 
     The invention could also be implemented to very great advantage in a twin-strand casting installation, in which two strands are supplied with molten metal by a tundish vessel with two outlet pipes. In this case, two housings, each with two casting rolls, would be used, one next to the other. An on-the-fly replacement could be accomplished here by replacing the one or other housing while casting continues with the other. 
     Instead of being positioned next to the casting rolls by manipulators  40 , the lateral sealing elements could in principle be mounted on the structural frame and moved away into the servicing position along with the structural frame. The housing  30  could also remain in the casting position. In that case, only the structural frame, equipped with appropriate wheels, and the casting rolls would be moved away. 
     In principle, other means of moving the structural frame and the casting rolls such as, for example, suspension rails or an air-cushion bed could be used instead of rails. 
     The housing could also be guided along continuous rails without a section which can be lowered. The water line connections would in that case have to be designed as plug-in connections, as a media pressure plate, or the like.