Method and plant for producing flat rolled products

Abstract

The invention concerns a method and a plant for producing flat rolled products, in order to obtain strips having a multiple crown transverse profile that subsequently have to be divided in a longitudinal direction into strips of a smaller width; the method provides a rolling step carried out in a rolling mill comprising roughing stands and finishing stands equipped with respective work rolls, in order to supply a strip of a determinate width.

1 . Method for producing flat rolled products, in order to obtain strips with a multiple positive crown transverse profile, which provides a rolling step carried out in a rolling mill comprising finishing stands equipped with respective work rolls, in order to supply a strip of a determinate width, wherein at least the work rolls of at least the last finishing stand are provided to have a profile with multiple negative crown, wherein the number of crowns present in the profile of the work rolls is correlated to the number of portions into which the rolled strip produced is subsequently divided in a longitudinal direction. 
     
     
         2 . Method as in  claim 1 , wherein the work rolls are provided to have an axial shifting movement, and wherein said axial shifting movement allows to modify the position of the crowns of the work rolls with respect to the position of the strip. 
     
     
         3 . Method as in  claim 1 , wherein the last three finishing stands have work rolls with the same diameter and same profile, and wherein the profile of the work rolls with multiple negative crown is applied in said last three finishing stands. 
     
     
         4 . Method as in  claim 1 , wherein the equations of the curve of the shaped profile of the work rolls are as follows:
     D   t ( y )= D−C  sin α/ b ( y−δ   s −δ 0 )+ a   1 ( y−δ   s −δ 0 )+ a   3 ( y−δ   s −δ 0 ) 3  
       D   b ( y )= D+C  sin α/ b ( y+δ   s +δ 0 )+ a   1 ( y δ s +δ 0 )+ a   3 ( y+δ   s +δ 0 ) 3  
   wherein   Dt(y) is the diameter of the upper work roll;   Db(y) is the diameter of the lower work roll;   D is the nominal diameter of the work roll;   α is the angle of the modifiable shape of the curve of the gap between the work rolls;   b is the barrel length of the work roll;   C is the amplitude of sine curve;   δ 0  is the value of the primary displacement of the shaped curve of the work roll;   δs is the value of the relative movement from the primary position;   a 1  is a first coefficient;   a 3  is a second coefficient;   and wherein by acting on the parameters α and C the multiple crown profile is determined in relation to the number of portions of strip into which the strip has to be divided.   
     
     
         5 . Method as in  claim 1 , wherein in the case of a double crown profile, there is provided a differentiated cooling with minimum cooling intensity around the central zone of the work roll and maximum cooling intensity in correspondence with the zone of the work roll that operates in correspondence with the central part of the two halves of the rolled strip. 
     
     
         6 . Plant for producing flat rolled products, in order to obtain strips with a multiple positive crown transverse profile, comprising at least one unit of finishing stands with work rolls, wherein in order to obtain a strip which, in a subsequent step and in a moment that follows the end of the rolling, will be longitudinally sectioned into multiple portions, at least the last finishing stand of the finishing unit comprises work rolls having a multiple negative crown profile, wherein the number of crowns present in the profile of the work rolls is correlated to the number of portions into which the strip will be divided. 
     
     
         7 . Plant as in  claim 6 , wherein at least the last three stands of the finishing unit have work rolls having a multiple negative crown profile. 
     
     
         8 . Plant as in  claim 6 , wherein at least the work rolls are equipped with an axial shifting movement, wherein the magnitude and direction of the axial shifting movement is correlated to obtaining a desired profile to be obtained on the strip (S). 
     
     
         9 . Plant as in one or the other of claims from 6, configured to operate in either one and/or the other of endless, semi-endless or coil-to-coil modes. 
     
     
         10 . Plant as in  claim 6 , comprising a differentiated system for cooling the work rolls with cooling intensity able to be adjusted as a function of the multiple negative crown shaped profile of the work rolls. 
     
     
         11 . Plant as in  claim 10 , wherein said cooling system comprises a plurality of cooling ramps each comprising delivery nozzles disposed adjacent to each other, with a determinate pitch, in double or triple rows and connected in groups to respective feed pipes, independent from each other, so as to define independent and differentiated cooling zones on the width of the rolls, wherein each pipe is equipped with a proportional valve that regulates the flow rate to the respective nozzles. 
     
     
         12 . Work roll for a finishing stand of a rolling plant for strips, comprising a multiple negative crown profile, wherein the number of crowns present in the profile of said work roll is correlated to the number of portions into which the strip produced is intended to be divided longitudinally.