Method to control the axial forces generated between the rolling rolls

Abstract

Method to control the axial forces generated between the rolls in a rolling stand ( 10 ) for plane products ( 12 ) having at least a pair of working rolls ( 11 a, 11 b ), a corresponding pair of back-up rolls ( 13 a, 13 b ) and at least an intermediate roll ( 15 a ) located between one of the working rolls ( 11 a ) and a corresponding back-up roll ( 13 b ), axial translation means ( 16 ) associated with the working rolls ( 11 a ) to translate them axially (WR shifting), crossing means ( 19 ) associated with the intermediate roll ( 15 a ) to arrange it with its longitudinal axis ( 25 a ) inclined (IR crossing), that is, rotated on a horizontal plane by a set angle (α) with respect to the longitudinal axes ( 21 a, 21 b, 23 a, 23 b ) of the working rolls ( 11 a, 11 b ) and of the back-up rolls ( 13 a, 13 b ); according to this method the WR shifting and the IR crossing are controlled by control means ( 30 ) so as to reduce to a minimum the axial forces generated in the working rolls ( 11 a, 11 b ), and consequently the axial load on the corresponding thrust bearings ( 28 ).

1 - Method to control the axial forces generated between the rolls in a rolling stand ( 10 ) for plane products ( 12 ) having at least a pair of working rolls ( 11   a,    11   b ), a corresponding pair of back-up rolls ( 13   a,    13   b ) and at least an intermediate roll ( 15   a ) located between one of said working rolls ( 11   a ) and a corresponding back-up roll ( 13   b ), axial translation means ( 16 ) associated with said working rolls ( 11   a ) to axially translate said working rolls (WR shifting), crossing means ( 19 ) associated with said intermediate roll ( 15   a ) to dispose said intermediate roll ( 15   a ) with its longitudinal axis ( 25   a ) inclined, that is, rotated on a horizontal plane by a set angle (α) with respect to the longitudinal axes ( 21   a,    21   b,    23   a,    23   b ) of said working rolls ( 11   a,    11   b ) and of said back-up rolls ( 13   a,    13   b ) (IR crossing), the method being characterized in that said WR shifting and said IR crossing are controlled by control means ( 30 ) so as to reduce to a minimum the axial forces generated in said working rolls ( 11   a,    11   b ), and consequently the axial load on the corresponding thrust bearings ( 28 ).  
     
     
         2 - Method as in  claim 1 , characterized in that said shifting of the working rolls ( 11   a,    11   b ) is made during rolling and that said control means ( 30 ) control said axial translation means ( 16 ) so that the axial force (F S ) generated between the product ( 12 ) being rolled and the corresponding working roll ( 11   a ) due to the shifting of the latter is in the opposite direction to the axial force (F WR ) generated by the crossing of the intermediate roll ( 15   a ) with respect to the corresponding working roll ( 11   a ).  
     
     
         3 - Method as in  claim 1 , characterized in that, once the direction of shifting of said working rolls ( 11   a  and  11   b ) has been established, according to the rolling session chosen, that is, with the width of the product ( 12 ) being rolled preferably decreasing from a maximum width (l max ) to a minimum width (l min ), the crossing of said intermediate roll ( 15   a ) is actuated, inclining it clockwise or anti-clockwise, so that the two corresponding axial forces generated (F WR  and F S ) have opposite directions.