The invention provides a method for carrying out online automatic accurate amplitude-
cutting control on spraying width of secondary cooling water of a wide and thick slab, belonging to the technical field of control over cooling water for
continuous casting and aiming at overcoming the defects of large
engineering modification of a cooling
water supply loop, higher cost or poorer control precision of manually adjusting spraying width and the like existing in the prior art. The method mainly comprises the following steps of: taking secondary cooling water spraying widths of different steel types and different width specifications of
casting blanks, which are determined through temperature
field simulation computation of secondary cooling water regions of the
casting blanks and
field tests,as references, driving a guide device mainly consisting of a support frame and a collecting guide
pipe to collect and guide out redundant cooling water which is sprayed from spray pipes at edge partsof rows of the inner arc of the sector section so as to realize online accurate amplitude-
cutting to spraying width of the secondary cooling water of the inner arc of the sector section. Due to adoption of the method disclosed by the invention, temperature of the corner of a
continuous casting blank can be stably controlled at 870-900 DEG C, a third
brittleness temperature region of steel is effectively avoided, the micro transverse crack defect rate of the corner of the micro
alloy steel
continuous casting blank is controlled within 1 percent.