Step-by-step cooling method of laminar cooling system of steckel mill for medium and heavy plates

The invention relates to the technical field of ferrous metallurgy, in particular to a step-by-step cooling method of a laminar cooling system of a steckel mill for medium and heavy plates, which is suitable for steel plates and steel coils produced in a rolling manner. A plurality of sets of laminar flow upper collecting pipes and laminar flow lower collecting pipes are sequentially arranged above and below a laminar flow roller way in the length direction of the laminar flow roller way to form a laminar flow cooling area, the number of basic starting sets of cooling water of a laminar flow cooling system is selected, and according to the length of a current rolled piece and the finish rolling temperature curve condition of a rolling mill, the rolling temperature of the rolling mill is calculated. And setting the length of the rolled piece for adding laminar cooling water step by step and the number of groups for adding water, and closing all laminar headers after the rolled piece is discharged from the lami