Rolling method

Abstract

A method of rolling a metal plate from an ingot or thick slab ( 1,2 ) includes setting a work roll gap with a mechanical screw ( 24 ) and rolling the ingot or slab through a first pass to produce a rolled product ( 21 ). The rolled product ( 21 ) is removed from the roll gap and the mechanical screw ( 24 ) is used to set a reduced roll gap ( 34 a ). The rolled product ( 21 ) is rolled through the reduced roll gap ( 34 a ) over a partial pass extending over less than the full length of the rolled product ( 21 ), to form a further rolled product ( 22, 21 ); and the further rolled product is removed from the roll gap. Repeat prior step. Then turn the rolled plate and carrying out a further roll pass in a width direction of the plate.

1 . A method of rolling a metal plate from an ingot or thick slab in a screwdown mill featuring rolls defining a roll gap between the rolls and a mechanical roll gap screw, the method comprising:
 setting a first work roll gap between the rolls defining the roll gap, using the mechanical roll gap adjusting screw, rolling the ingot or slab through a first pass extending through the first roll gap over the full length of the ingot or slab in the rolling direction to produce a first rolled product;   removing the first rolled product from the first roll gap after the first pass;   operating the first roll gap mechanical screw to set a second, reduced work roll gap reduced from the first roll gap;   performing a first rolling iteration comprising rolling the first rolled product through the second, reduced roll gap over a partial pass, the partial pass extending over less than the full length of the first rolled product in the rolling direction, to form a second rolled product;   removing the second rolled product from the roll gap at conclusion of the first iteration;   then turning the second rolled product through 90° and performing a further roll pass on the second rolled product in a width direction broadsiding the second rolling product to form a further rolled product.   
     
     
         2 . A method according to  claim 1 , further comprising:
 after removing the further rolled product from the roll gap and prior to the turning of the further rolled product, operating the roll gap mechanical screw to set a further third reduced roll gap; and   rolling the still further rolled product through the further third reduced roll gap over a partial pass, the partial pass extending in the rolling direction over less in the rolling direction than the full length of the further rolled product.   
     
     
         3 . A method according to  claim 1 , further comprising:
 successively repeating the steps each time of removing the then further rolled product from the roll gap, operating the mechanical screw to successively set each time a further reduced roll gap, and rolling the then further product over a successive partial pass; and   repeating the steps for a set number of iterations to produce a rolled plate.   
     
     
         4 . A method according to  claim 3 , further comprising selecting a number of the iterations according to parameters of required yield loss and rolling time. 
     
     
         5 . A method according to  claim 1 , further comprising counting a number of revolutions of the roll as the rolled product is removed from the roll gap for setting the next roll gap for obtaining a difference in thickness between adjacent roll gap thickness settings; using the number of revolutions and the difference in thickness for calculating the then length of the rolled product for thereby deriving the length of the rolled product to be rolled at the next rolling stage. 
     
     
         6 . A method according to  claim 3 , wherein each partial pass through a successively further reduced roll gap is of a length over the product less than the length over the product over the length of the respective partial pass over the preceding roll product that had passed the preceding roll gap. 
     
     
         7 . A method according to  claim 6 , wherein the lengths of the successive partial passes are selected to define a stepped surface of the product which has passed through a respective successive roll gap in each partial pass.