Method and device for guiding cast billets in a continuous casting facility

Abstract

The invention relates to a method for guiding strands in a continuous casting installation, in particular an installation for producing thin slabs made of steel, having an ingot mold and a strand-guidance frame which is provided with a cooling device. In this case, heat is extracted indirectly from the strand after it leaves the ingot mold, and the strand, at least in sections, is held in shape, guided in the strand discharge direction and additionally cooled by means of a gaseous medium. Furthermore, the strand is additionally moved in a defined manner and at a predeterminable speed through the strand frame by mechanical means, the speed of the strand being accelerated or decelerated. The invention furthermore relates to a device for carrying out the method. See FIG. 1.

1 . A method for guiding strands in a continuous casting installation, in particular an installation for producing thin slabs made of steel, having an ingot mold and a strand-guidance frame which is provided with a cooling device, wherein heat is extracted indirectly from the strand after it leaves the ingot mold, wherein at least in sections the strand is 
 held in shape    guided in the direction of the strand discharge, and    additionally cooled    by means of a gaseous medium, wherein a stream of gas is directed onto the strand surface in such a way as to influence the strand speed, and wherein the strand is additionally moved in a defined manner and at a predeterminable speed through the strand frame by mechanical means, namely continuous casting rolls, the speed of the strand being accelerated or decelerated.    
     
     
         2 . The method as claimed in    claim 1   , wherein the gaseous medium can be set in a predeterminable manner with regard to the volume and the pressure as a function of the shell thickness.  
     
     
         3 . The method as claimed in    claim 1   , wherein the thickness of the strand at the ingot mold outlet is reduced in at least one plate segment.  
     
     
         4 . A continuous casting device for producing strands, in particular thin slabs made of steel, having an ingot mold, which is followed in the casting direction by a strand-guidance frame which has rolls bearing against the strand surface and plates provided with bores, and having components for cooling the strand surface, 
 for carrying out the method as claimed in    claim 1   ,    wherein the plates ( 30 ) are divided into segments ( 31 ), between which rolls ( 21 ) are provided, wherein a network of distribution lines ( 43 ,  44 ,  45 ), through which a gaseous medium can be supplied, is provided in the plate segments ( 31 ) on the side inclined toward the strand (B), wherein the distribution lines ( 43 ,  44 ,  45 ) are connected to one another in sections and via collection lines ( 46 ) are connected to a gas-conveying station ( 49 ) wherein the mouths ( 42 ) of the distribution lines ( 43 ,  44 ,  45 ) are arranged, at an angle which is inclined with respect to the direction of travel of the strand (B), in that wall ( 32 ) of the plate segment ( 31 ) which is inclined toward the strand (B), wherein the wall ( 32 ) which is inclined toward the strand (B) is constructed in terms of shape and material in such a manner that it is possible to dissipate the maximum possible amount of radiant heat from the strand shell (W), and wherein the plate segments ( 31 ), at least in the edge region ( 34 ), are arranged at a distance from the strand surface allowing a defined leakage of the gaseous medium.    
     
     
         5 . The continuous casting device as claimed in    claim 4   , wherein a wear-resistant layer, e.g. nickel and/or chromium, is applied to the wall ( 32 ) which is inclined toward the strand (B).  
     
     
         6 . The continuous casting device as claimed in    claim 3   , wherein the plate segments ( 31 ) are composed of pipes ( 38 ) which are arranged in meandering form and through which a cooling medium flows, with the distribution lines ( 43 ,  44 ,  45 ) provided perpendicular to the pipe guidance at the lines ( 39 ) where the pipes are in contact with one another.  
     
     
         7 . The continuous casting device as claimed in    claim 4   , wherein means ( 51 ) are provided for independently adjusting the distance between the plates and the strand (B).  
     
     
         8 . The continuous casting device as claimed in    claim 4   , wherein the plate segments ( 31 ) are designed as cushions ( 33 ) which, in the edge region, have a lip ( 34 ) which affects the leakage of the gaseous medium and also the dissipation of heat from the strand (B).  
     
     
         9 . The continuous casting device as claimed in    claim 8   , wherein the wall thickness (d) of the wall ( 32 ) of the plate segments ( 31 ) decreases toward the principal axis of the plate.  
     
     
         10 . The continuous casting device as claimed in    claim 4   , wherein that wall ( 32 ) of the plate segments ( 31 ) which is inclined toward the strand (B) is of concave configuration in the direction of travel of the strand (B).  
     
     
         11 . The continuous casting device as claimed in    claim 10   , wherein the extent of the concavity of the wall ( 32 ) decreases in the direction of travel of the strand (B) and becomes zero at the end of the strand-guidance frame having the plate segments ( 31 ).  
     
     
         12 . The continuous casting device as claimed in claims  11  or  7 , wherein the means ( 51 ) are pneumatic actuators which are provided at least in the first position of the first plate segment  31  downstream of the ingot mold ( 12 ).  
     
     
         13 . The strand-guidance frame as set forth in    claim 4   , wherein the number of distribution lines ( 43 ,  44 ,  45 ) in the plate segment ( 31 ) can be varied functionally depending on the metallurgical length, taking into account the membrane effect of the strand shell thickness.  
     
     
         14 . The strand-guidance frame as set forth in    claim 4   , wherein the internal diameter of the distribution lines ( 43 ,  44 ,  45 ) in the plate segment ( 31 ) is adapted in functional terms over its metallurgical length in order to do a predeterminable amount of work in accordance with its geometric location while supplying the same amount of pressure.  
     
     
         15 . The continuous casting device as claimed in    claim 4   , wherein the rolls ( 21 ) arranged between the plate segments ( 31 ) are connected to an adjustable roll drive ( 22 ), by means of which their rotational speed and tensile force can be set.  
     
     
         16 . The continuous casting device as claimed in one of the preceding claims, wherein the plate segments ( 31 ), the rolls ( 21 ) and the strand (B) are surrounded by a housing ( 61 ), which via a system of lines ( 62 ,  63 ) is connected to a gas cooling ( 64 ) and purification installation ( 65 ).  
     
     
         17 . The continuous casting device as claimed in    claim 16   , wherein the system of lines ( 62 ,  63 ) is designed in such a way that the gas, for example nitrogen, can be fed back to the compressor after being purified and cooled.