Strand guiding device and method for guiding a metal strip

Abstract

The invention relates to a strand guiding device and a method for guiding a metal strip, in particular a metal strip that has not yet solidified right through, in a continuous casting installation. Known strand guiding devices comprise a segment frame and at least one pair of opposing guiding rollers, between which the metal strip is guided. At least one of the guiding rollers takes the form of at least two part-rollers 122, 124 arranged next to each other. The part-rollers are mounted on the segment frame 110 by means of two outer bearings 132, 134 and at least one common intermediate bearing 133 . To provide at least partial compensation for the segment frame 110 springing up or bending, caused indirectly by the ferrostatic pressure in the interior of the metal strip that is not yet solidified right through and occurring in particular in the region of the intermediate hearing 133 during the transport of the metal strip between the guiding rollers 120 , three different means are proposed according to the invention, means which can also to used in combination will one another. These means are a bowing of the intermediately mounted guiding roller and/or a more yielding form of the outer bearings 132, 134 in comparison with the intermediate bearing 133 and/or a greater distance A 1 between the segment frame 110 and the centre axis M of the part-rollers 122, 124 in the case of the intermediate bearing 133 in comparison with the outer bearings 132, 134.

1 . A strand-guiding apparatus of a continuous-casting installation for guiding a metal strip that has not yet completely solidified, in particular, a thin slab, comprising:
 a section frame ;   at least one pair of opposing guide rollers that span a variable roller gap through which the metal strip is passed, wherein at least one of the guide rollers is designed in the form of two adjacent aligned subrollers;   two outer bearings and at least one common center bearing supporting the at least two subrollers on the section frame; and   means for at least partially compensating for a spring-back of the section frame in the area of the center bearing when the metal strip is conveyed through the roller gap;   
     wherein the means is designed
 in the form of a bowing of the centrally supported guide roller ; or 
 in the form of a more yielding design of the outer bearings as compared with the center bearing; or 
 in the form of a greater distance between the section frame and the center axis of the subrollers at the center bearing than at the outer bearings. 
 
   
   
       2 . The strand-guiding apparatus according to  claim 1  wherein in order to effect the bowing of a single centrally supported guide roller the two subrollers are each designed as tapered with a straight or convex shape, and are each supported by their thicker ends on the common center bearing. 
   
   
       3 . The strand-guiding apparatus according to  claim 1  wherein the bowing of the subrollers or of the guide roller is designed to be parabolic or as determined by a polynomial function. 
   
   
       4 . The strand-guiding apparatus according to  claim 1  wherein the more-yielding design of the outer bearings as compared with the center bearing is implemented by a comparatively softer suspension at the outer bearings. 
   
   
       5 . The strand-guiding apparatus according to  claim 1  wherein when multiple center bearings are present the center bearings are suspended in increasingly firmer fashion toward the center of the metal strip. 
   
   
       6 . The strand-guiding apparatus according to  claim 5  wherein the center bearing is/are designed as rigid in the area of the center of the metal strip. 
   
   
       7 . The strand-guiding apparatus according to  claim 1  wherein when a plurality of guide roller pairs disposed one after the other in the travel direction of the metal strip is present at least certain of the means according to the invention for compensating for the spring-back of the section frame are calibrated to be increasingly stronger at the guide rollers in the travel direction of the metal strip. 
   
   
       8 . The apparatus according to  claim 7 , further comprising control means whereby the counter-pressure exerted by the strand-guiding apparatus on the strand shell tends to become increasingly larger so as to compensate a spring-back of the section frame in the travel direction of the metal strip. 
   
   
       9 . In combination with a continuous-casting unit producing a strand extending and traveling in a longitudinal travel direction and having a solid shell and a liquid core, a strand-guiding apparatus comprising:
 a plurality of longitudinally spaced section frames;   respective pairs of roller assemblies carried on the frames, transversely flanking and bearing transversely on the strand, each pair forming a gap through which the strand passes, each roller assembly being formed by two aligned subrollers;   a respective center bearing between the subrollers of each roller assembly and bracing inner ends of the respective subrollers transversely against the respective frame;   respective outer rollers at outer ends of the subrollers of each roller assembly bracing the respective outer ends transversely against the respective frame, the subrollers being shaped or being supported on the respective frame such that in an unloaded condition the gap is transversely narrower at the center bearing than at the outer bearing.   
   
   
       10 . The apparatus defined in  claim 9  wherein the subrollers have outer surfaces engageable with the strand and centered on respective axes. 
   
   
       11 . The apparatus defined in  claim 10  wherein the subrollers are tapered axially away from the center bearing. 
   
   
       12 . The apparatus defined in  claim 10  wherein the subrollers are substantially cylindrical and the axes of the subrollers of each roller assembly meet at a large acute angle at the respective center axis. 
   
   
       13 . The apparatus defined in  claim 10  wherein the outer bearings include cushioned supports by means of which they are more transversely deflectable than the respective center bearings. 
   
   
       14 . The apparatus defined in  claim 9  wherein the subrollers are shaped or supported so as to offer increasing resistance to transverse deflection downstream from the continuous-casting unit.