Method of cooling hot-rolled steel plate

A method of cooling a hot-rolled steel plate in which, while a hot-rolled steel plate P is being advanced lengthwise, the distribution of cooling water supplied to the opposite surfaces of said steel plate P is controlled along the length and width of said steel plate P through a plurality of nozzles disposed adjacent to said opposite surfaces of said steel plate P and in the lengthwise and widthwise directions of a predetermined cooling zone provided along a passage through which said steel plate P is advanced, thereby water cooling said steel plate P to a predetermined temperature at a predetermined cooling velocity, which comprises the steps of:

• detecting, at a first group of temperature measurement points which are present over the width of said steel plate P, the temperatures in a plurality of cross-sectional areas in the thicknesswise direction at predetermined lengthwise positions of said steel plate P;
• and further detecting temperatures at a second group of temperature measurement points which are present along said width in said cross-sectional areas, before, during and after water cooling;
• calculating the temperature differences between said detected temperatures at said first and second temperature measurement points in the direction of said width and said thickness along said width, each time the detection is performed;
• forecasting the extent of bending deformation in widthwise and lendthwise directions of said steel plate P after said cooling process, on the basis of said obtained temperature differences, each time the calculation is performed;
• and
• controlling and correcting, by means of said plurality of nozzles, the distribution of the rate at which cooling water is being supplied to a steel plate and the rate at which said cooling water should be supplied to the ensuing steel plates whenever said forecasted extent of deformation exceeds an allowable range.