Method and device for cooling and stabilizing strip in a continuous line

Abstract

The invention concerns a method for cooling metal strips using cooling chambers by blowing a gas, in a continuous heat treatment line, wherein: the chambers ( 4,4 a . . . 4′, 4′ a . . . ) have a unitary dimension (h) in the moving direction (X) of the strip less than two meters and are split along the direction perpendicular to the moving direction (X) of the strip into a plurality of unitary blowing sectors; each unitary blowing sector is equipped with at least one blowing pressure sensor ( 7 ) and with at least one actuator ( 2 ) for adjusting the pressure of each of said unitary sectors; and a controlling and regulating system controls the actuators ( 2 ) such that the longitudinal theoretical distribution of pressure in the blowing sectors corresponding to a cooling curve of the target strip is adapted so as to take into account a modification of the position of the strip relative to the blowing sectors to avoid any contact thereof with the walls of the devices of the cooling zone without modifying the cooling curve.

1 . A method of cooling a metal strip by cooling boxes that cool by blowing a gas, in particular air or a mixture consisting of nitrogen and hydrogen, in a continuous heat treatment line, wherein:
 the boxes ( 4 ,  4   a  . . .  4 ′,  4 ′ a  . . . ) have a unitary dimension (h) in the run direction (X) of the strip of less than two meters and are divided in the direction perpendicular to the run direction (X) of the strip into a plurality of unitary blowing sectors ( 4 α,  4 β,  4 γ . . .  4   a α,  4   a β,  4   a γ . . . ;  4 ′α,  4 ′β,  4 ′γ . . .  4 ′ a α,  4 ′ a β,  4 ′ a γ . . . );   each unitary blowing sector is equipped with at least one actuator ( 6 ;  2 ) for adjusting the pressure of each of these unitary sectors; and   a control/regulation system (R) controls the actuators ( 6 ;  2 ) in such a way that the theoretical longitudinal pressure distribution in the blowing sectors corresponding to an intended strip cooling curve (F) is adapted so as to take into account a change in the position of the strip relative to the blowing sectors, so as to avoid any contact of said strip with the walls of the equipment in the cooling zone without modifying the cooling curve (F).   
   
   
       2 . The method as claimed in  claim 1 , wherein:
 each unitary blowing sector is equipped with at least one sensor ( 7 ) for measuring the blowing pressure and with at least one actuator ( 6 ;  2 ) for adjusting the pressure in each of these unitary sectors; and   the information coming from the sensors ( 7 ) is sent to the control/regulation system (R) that controls the actuators ( 6 ;  2 ) in such a way that the theoretical longitudinal pressure distribution in the blowing sectors corresponding to an intended strip cooling curve (S) is adapted so as to take into account a change in the position of the strip relative to the blowing sectors so as to avoid any contact of said strip with the walls of the equipment in the cooling zone without modifying the cooling curve (F).   
   
   
       3 . The method as claimed in  claim 1 , wherein:
 each unitary blowing sector is equipped with at least one device ( 8 ) for measuring the blowing flow rate and at least one actuator ( 6 ;  2 ) for adjusting the pressure in each of these unitary sectors; and   the information coming from the devices ( 8 ) for measuring the blowing flow rate is sent to the control/regulation system (R) that controls the actuators ( 6 ;  2 ) in such a way that the theoretical longitudinal pressure distribution in the blowing sectors corresponding to an intended strip cooling curve (F) is adapted so as to take into account a change in the position of the strip relative to the blowing sectors so as to avoid any contact of the latter with the walls of the equipment in the cooling zone without modifying the cooling curve (F).   
   
   
       4 . The method as claimed in  claim 1 , wherein each box ( 4 ,  4   a  . . . ,  4 ′,  4 ′ a  . . . ) is divided into at least two unitary blowing sectors over the width of the strip for a right/left correction, or at least three blowing sectors for a center/edge correction. 
   
   
       5 . The method as claimed in  claim 1 , wherein the control/regulation system is programmed so as:
 in a first step, to define, per “longitudinal slice”, the pressure setpoints for each box ( 4 ,  4   a  . . .  4 ′,  4 ′ a  . . . ) according to the cooling curve to be obtained; and   in a second step, if a correction to the position of the strip ( 1 ) is demanded and depending on the type of correction introduced, manually or automatically, to modify the pressure distribution in a given longitudinal “slice” of the cooler so as to obtain the desired strip position correction while keeping the selected cooling curve intact.   
   
   
       6 . The method as claimed in  claim 1 , wherein the control/regulation system (R) takes into account setpoints for setting the pressure in one or more blowing sectors so as to adjust the pressure settings in the other blowing sectors so that the strip ( 1 ) is placed in a position that avoids any contact of the latter with the walls of the equipment in the cooling zone and that, at any point on the strip, the temperature follows a desired theoretical cooling curve (F). 
   
   
       7 . The method as claimed in  claim 1 , wherein the pressures adjusted on either side of the strip so as to correct the position of the strip ( 1 ) are defined so that their resultant achieves the overall thermal objective defined for the section in question and over the entire width of the strip, depending on the desired theoretical cooling curve. 
   
   
       8 . The method as claimed in  claim 1 , wherein the control/regulation system (R) determines:
 in a first step, according to the theoretical cooling curve (F), the characteristics of the strip ( 1 ) and the data on the entire installation, an overall cooling power for the pairs of two unitary cooling sectors located on either side of a given zone of the strip; and   in a second step, according to the desired position of the strip in the zone in question, the blowing pressures for the two unitary sectors of each pair, which pressures, while providing the desired overall cooling, may be different so as to adjust the position of the strip.   
   
   
       9 . The method as claimed in  claim 1 , wherein the pressures in the unitary sectors ( 4 α,  4 β, . . .  4   a α,  4 ′ a β . . . ) of several boxes located on one side of the strip are adjusted simultaneously, namely increased or decreased, so as to apply a correction to the position of the strip ( 1 ) parallel to itself. 
   
   
       10 . The method as claimed in  claim 1 , wherein the pressures in the unitary sectors of a given level ( 4 α,  4 β, . . .  4   a α,  4   a β . . . ) located on each side of the strip are adjusted so as to apply a correction to the position of the strip ( 1 ) as a twist about its main axis. 
   
   
       11 . The method as claimed in  claim 1 , wherein for holding the strip in position, an alternating setting of the pressure along the run direction of the strip ( 1 ) is provided in the cooling boxes, with a higher pressure in one box followed by a lower pressure in the next box placed on the same side as the strip, and a higher pressure in one box corresponds to a lower pressure in the box facing it on the other side of the strip so as to produce an alternating deformation of the strip. 
   
   
       12 . The method as claimed in  claim 1 , wherein the setpoints for setting the pressure in the blowing sectors is delivered by a computer on the basis of a thermomechanical model that takes into account the nature of the material of the strip and the heat treatment to be applied to the strip. 
   
   
       13 . The method as claimed in  claim 12 , wherein the algorithm for controlling the cooling curve and for stabilizing the position of the strip uses fuzzy logic and/or neural systems. 
   
   
       14 . A device for cooling a metal strip in a continuous heat treatment line, comprising cooling boxes ( 4 ,  4   a  . . . ,  4 ′,  4 ′ a  . . . ) which cool by blowing a gas, in particular air or a mixture consisting of nitrogen and hydrogen, which follow one after another in the run direction (X) of the strip, wherein:
 the boxes ( 4 ,  4   a  . . . ,  4 ′,  4 ′ a  . . . ) have a unitary dimension (h) in the run direction (X) of the strip of less than two meters and are divided in the direction perpendicular to the run direction (X) of the strip into a plurality of unitary blowing sectors ( 4 α,  4 β, . . .  4   a α,  4   a β, . . . ;  4 ′α,  4 ′β,  4 ′ a α,  4 ′ a β, . . . );   each unitary blowing sector is equipped with at least one actuator ( 6 ;  2 ) for adjusting the pressure in each of these unitary sectors along directions parallel and perpendicular to the run direction of the strip; and   a control/regulation system (R) is provided, which system controls the actuators ( 6 ;  2 ) in such a way that the strip is placed in a position that avoids any contact of said strip with the walls of the equipment in the cooling zone and that, at any point on the strip, the temperature follows a desired theoretical cooling curve (F).   
   
   
       15 . The device as claimed in  claim 14 , wherein each blowing sector is equipped with at least one sensor ( 7 ) for measuring the blowing pressure and with at least one actuator ( 6 ;  2 ) for adjusting the pressure in each of these unitary sectors, and the information coming from the sectors ( 7 ) is sent to the control/regulation system (R) that controls the actuators ( 6 ;  2 ) in such a way that the theoretical longitudinal pressure distribution in the blowing sectors corresponding to an intended strip cooling curve (F) is adapted so as to take into account a change in the position of the strip relative to the blowing sectors so as to avoid any contact of said strip with the walls of the equipment in the cooling zone without modifying the cooling curve (F). 
   
   
       16 . The device as claimed in  claim 14 , wherein each unitary blowing sector is equipped with at least one device ( 8 ) for measuring the blowing flow rate and with at least one actuator ( 6 ;  2 ) for adjusting the pressure in each of these unitary sectors, and the information coming from the devices ( 8 ) for measuring the blowing flow rate is sent to the control/regulation system (R) that controls the actuators ( 6 ;  2 ) in such a way that the theoretical longitudinal pressure distribution in the blowing sectors corresponding to an intended strip cooling curve (F) is adapted so as to take into account a change in the position of the strip relative to the blowing sectors so as to avoid any contact of said strip with the walls of the equipment in the cooling zone without modifying the cooling curve (F). 
   
   
       17 . The device as claimed in  claim 14 , wherein each box is divided into at least two unitary blowing sectors over the width of the strip for a right/left correction, or at least three blowing sectors for a center/edge correction. 
   
   
       18 . The device as claimed in  claim 14 , wherein the control/regulation system (R) is designed to adjust all the pressures in the unitary sectors of the cooling zone according to a given pressure map in the directions parallel and perpendicular to the run direction of the strip by the choice of setpoints introduced into the system (R) in such a way that the settings obtained are adapted according to the nature of the strip and to the transverse profile of the strip upon entering the cooling section. 
   
   
       19 . The device as claimed in  claim 14 , wherein the control/regulation system (R) is designed to make, when necessary, an adjustment to all the pressures in the boxes in the cooling zone, which results mainly in a correction to the position of the strip ( 1 ) parallel to itself. 
   
   
       20 . The device as claimed in  claim 14 , wherein the control/regulation system (R) is designed to make, when necessary, an adjustment to all of the pressures in the boxes of the cooling zone, which results mainly in a correction to the position of the strip ( 1 ) as a twist about its main axis. 
   
   
       21 . The device as claimed in  claim 14 , wherein the control/regulation system (R) is designed to make, when necessary, an adjustment to all of the pressures in the boxes of the cooling zone, which results mainly in a correction to the position of the strip ( 1 ) so as to produce an alternating deformation of the strip along its longitudinal direction. 
   
   
       22 . The device as claimed in  claim 14 , wherein the automatic control/regulation system (R) is programmed so as to determine:
 in a first step, according to the theoretical cooling curve (F), overall data and characteristics of the strip ( 1 ), an overall cooling power for each of the pairs of two unitary cooling sectors located on either side of a given zone of the strip; and   in a second step, according to the desired position of the strip in the zone in question, the blowing pressures for the two unitary sectors of each pair, which pressures while still providing the desired overall cooling, may be different in order to adjust the position of the strip.