FOUR PERIPHERY FLAW PREVENTION HOT ROLLING METHOD FOR STEEL PLATE

PROBLEM TO BE SOLVED: To provide a method which eliminates a generation of a four periphery flow arising from an encroachment of an overlap portion in double bulge shape at the end face of the rolled material into a finished good width, and is capable to correspond easily and quickly in the middle of rolling and also applicable to a finish temperature designated material such as a controlled rolling material. SOLUTION: An end shape measuring instrument 1 such as a laser rangefinder is installed at each side of a roller table of a roughing mill, and in a middle point of a broad side pass rolling pass, the shape of the end face, which is parallel with a longitudinal direction L, of a slab S2 rotated 90 degrees is measured and the end face bulge shape and overlap quantities a1, a2 are recognized by the arithmetic processing of measurement result. Then in the case of a double bulge shape, it is judged whether the picking of the finished good width is possible or not when the broad side pass rolling is completed, and if the product width picking is impossible the broad side pass rolling pass schedule is recalculated, and based on this result the broad side pass rolling of the remainder is carried out, and the finished good width is ensured by the extension of the width of the rolled material, so that the overlap portion does not get in the finished good width.