Prior to the rolling of a flat rolling material (2) on a rolling line that includes a number of roll stands (1), a control system (3) receives actual variables (I) and target variables (Z) of the material (2). The control system (3) determines desired values (S*) for the roll stands (1), based on the actual (I) and target variables (Z) in combination with a model (10) of the rolling line, such that expected variables (E1) of the material (2) after its rolling are aligned as far as possible with the target variables (Z) and transfers the desired values (S*) to the roll stands (1) such that the material (2) is rolled according to the desired values (S*). The target variables (Z) comprise at least one freely selectable, discrete characteristic variable (K1 to K5, K2′ to K4′, K2″ to K4″) defining the contour (K) of the flat rolling material (2).

A provisional elongation strain difference distribution Δε(x) of a metal strip during rolling is found under conditions in which out-of-plane deformation of the metal strip is restrained. A critical buckling strain difference distribution Δε.sub.cr(x) is found based on the provisional elongation strain difference distribution Δε(x), a strip thickness and strip width of the metal strip, and tension acting on the metal strip at exit from a rolling mill. In cases in which the provisional elongation strain difference distribution Δε(x) exceeds the critical buckling strain difference distribution Δε.sub.cr(x), the difference between the provisional elongation strain difference distribution Δε(x) and the critical buckling strain difference distribution Δε.sub.cr(x) is found, and this difference is added to the provisional elongation strain difference distribution Δε(x) to find a true elongation strain difference distribution Δε′(x). Rolling conditions are set based on the true elongation strain difference distribution Δε′(x), and the metal strip is rolled, thereby controlling the profile of the metal strip.

A method of cooling control for a steel plate, a cooling control device, and a method of manufacturing a steel plate, which adjust an upper/lower water ratio and prevent C-warping during cooling. The method of cooling control includes: determining an upper/lower water ratio of a steel plate being cooled wherein at least one of a C-warping amount and a curvature is within a target permissible range, based on a past operating condition, a past upper/lower water ratio when cooling under the past operating condition has been implemented, and at least one of a past C-warping amount and a past curvature measured by a shape measuring meter at an outgoing side of a cooling zone when the cooling under the past operating condition is implemented; and adjusting an amount of cooling water to be blown onto the steel plate to reach the upper/lower water ratio.

Provided is a method for rolling a steel sheet and a method for manufacturing a steel sheet capable of preventing occurrence of defects in appearance of a steel sheet caused by oil spots of a coolant and preventing occurrence of defects in shape of a steel sheet by appropriately controlling thermal deformation of work rolls. The method for rolling a steel sheet according to the present invention is a method for rolling a steel sheet involving feeding of a coolant to rolls that form a rolling mill during the rolling. The method includes keeping a coolant feeding rate at or lower than a predetermined rate lower than an upper constant rate at a start of operation of the rolling mill, and increasing the coolant feeding rate to the upper constant rate in response to an amount of center buckles of the steel sheet reaching or exceeding an upper target value.

A cooling device cooling an undersurface of a hot rolled steel sheet that is being transported on transport rolls after finish rolling of a hot rolling step includes: width divided cooling zones that are a plurality of cooling zones into which a whole cooling zone is divided in a sheet width direction; divided cooling sections that are a plurality of cooling zones into which each of the width divided cooling zones is divided in the rolling direction; a water nozzle spraying cooling water over each of undersurfaces of the divided cooling sections; a switching mechanism switching the cooling water between impinging and not impinging on the divided cooling sections; a width direction thermometer measuring a temperature distribution in the sheet width direction; and a controller controlling operation of the switching mechanism.

A rolling line for rolling a flat rolling material (2) includes a number of roll stands (1). Prior to the rolling, a control system (3) receives actual variables (I) of the material (2) before the rolling and target variables (Z) after the rolling. The control system (3) determines desired control variables (S*) for the roll stands (1), based on the actual (I) and target variables (Z), in combination with a description (B) of the rolling line, using a model (10) of the rolling line. The control system (3) determines the desired values (S*) such that expected variables (E1) for the material (2) after its rolling are aligned as far as possible with the target variables (Z). The control system (3) transfers the desired values (S*) to the roll stands (1) such that the material (2) is rolled according to the transferred desired values (S*). The target variables (Z) comprise at least one freely selectable, discrete characteristic variable (K1 to K5, K2′ to K4′, K2″ to K4″) defining the contour (K) of the flat rolling material (2).

A cooling device cooling an undersurface of a hot rolled steel sheet that is being transported on transport rolls after finish rolling of a hot rolling step includes: width divided cooling zones that are a plurality of cooling zones into which a whole cooling zone is divided in a sheet width direction; divided cooling sections that are a plurality of cooling zones into which each of the width divided cooling zones is divided in the rolling direction; a water nozzle spraying cooling water over each of undersurfaces of the divided cooling sections; a switching mechanism switching the cooling water between impinging and not impinging on the divided cooling sections; a width direction thermometer measuring a temperature distribution in the sheet width direction; and a controller controlling operation of the switching mechanism.

A provisional elongation strain difference distribution (x) of a metal strip during rolling is found under conditions in which out-of-plane deformation of the metal strip is restrained. A critical buckling strain difference distribution .sub.cr(x) is found based on the provisional elongation strain difference distribution (x), a strip thickness and strip width of the metal strip, and tension acting on the metal strip at exit from a rolling mill. When the provisional elongation strain difference distribution (x) exceeds the critical buckling strain difference distribution .sub.cr(x), the difference between the provisional elongation strain difference distribution (x) and the critical buckling strain difference distribution .sub.cr(x) is found, and added to the provisional elongation strain difference distribution (x) to find a true elongation strain difference distribution (x). Rolling conditions are set based on the true elongation strain difference distribution (x), and the metal strip is rolled, thereby controlling the metal strip's profile.

A closed loop roller leveler assembly for measuring flatness of a strip, having a roller leveler, a flatness sensor, and at least one arm operatively connected to the flatness sensor to raise and lower the flatness sensor. The flatness sensor has a plurality of sensor rolls, at least one load cell, and at least one laser sensor which is mounted on a positioner which oscillates the laser sensors across a width of the strip.

A closed loop roller leveler system has a roller leveler; a flatness sensor; and at least one arm for raising and lowering the flatness sensor. The sensor includes a plurality of sensing rollers extending across a width of a strip of material. The sensor further has at least one load cell and at least one laser sensor for measuring the flatness level of the strip.