A method for manufacturing thick plate having rectangular edges

摘要

PURPOSE: A method for manufacturing a steel plate is provided to improve squareness of the corner part of the plate after lengthwise rolling by preventing edge projection of the corner part of a widthwise rolled plate caused by diameter differences of the sides of rotation rolls during the widthwise rolling process by a plate rolling mill. CONSTITUTION: The method for manufacturing a steel plate having superior corner squareness comprises the steps of performing level rolling on a slab so that a thickness of the slab is evenly leveled in a rolling mill; performing widthwise rolling on the level rolled pate after horizontally rotating the level rolled plate to an angle of 90 degrees on a rotation roller table; centering the widthwise rolled plate using a side surface guide plate for lengthwise rolling after rotating the widthwise rolled plate to an angle of 90 degrees on the rotation roller table; measuring a width and a length of the widthwise rolled plate using width and length measuring devices, and obtaining a skew angle(); obtaining a lengthwise reduction schedule based on the width and length information; judging whether the skew angle() comes within the permitted limit of the already set target skew angle(0) or not; performing lengthwise rolling in an ordinary manner when the skew angle() comes within the permitted limit of the target skew angle( 0), and obtaining a compensation angle(1) by the following mathematical expression 1 and an angle(2) between the diagonal line and the base line of the widthwise rolled plate by the following mathematical expression 2: £Mathematical Expression 1| 1=(SWepsx)/PLeps, where SWeps is a reduction ratio(%) during widthwise rolling, and PLeps is a reduction ratio(%) of the first pass of lengthwise rolling,£Mathematical Expression 2| 2=tan¬-1{w/(L+a)}; obtaining a rotation limit distance(K) by the following mathematical expression 3 using the obtained compensation angle(1) and the angle(2) between the diagonal line and the base line: and rotating the widthwise rolled plate as much as the obtained rotation limit distance(K) of the side surface guide plate, performing lengthwise 1 pass rolling the rotated plate, centering the lengthwise 1 pass rolled plate, and then manufacturing a plate by performing residual pass rolling on the centered 1 pass rolled plate in an ordinary manner.