Header opening method under controlled cooling after rolling

The invention discloses a header opening method under controlled cooling after rolling, used cooling equipment is divided into four areas A, B, C and D, each area is provided with six groups of headers, the total number of the headers is 24, the six groups of headers in the area A are independently controlled, the six groups of headers in each area B, C and D are integrally controlled and can only be opened or closed at the same time, and in the cooling process after rolling of a steel plate, according to process requirements, the number of the headers in each area B, C and D is reduced. The opening mode of the headers is controlled, and when the number n of the headers needing to be opened is smaller than or equal to 6, only n groups of the headers in the area A are opened from front to back; when the number n of the headers needing to be opened is larger than 6 and smaller than or equal to 12, the headers in the B area are opened, and n-6 headers in the A area are opened from back to front; when the number