METHOD OF ROLLING METAL WORKPIECE AND MILL THEREFOR

摘要

A method of rolling metal workpiece in a rolling mill consisting of rolling stands or pinch rolls, and more than one high reduction rolling stand disposed successively. The roll gap of the workrolls of the rolling stand at the rear side is set so that the corresponding contact angle ?? (?? = tan -1(cos .alpha. x tan ?) wherein a denotes contact angle between the workrolls in the bottom of the rolls groove and the workpiece, and .alpha. denotes inclined angle of the groove) is bigger than tan -1 .mu. (.mu. denotes a frictlon coefficient between the workpiece and the workrolls at the biting time) and also is smaller than tan -1 .mu.' (.mu.' denotes a friction coefficient between the workpiece and the workrolls when the workplece is completely bitten between the workrolls and the rolling is in progress). The workpiece is fed to the rolling stand of the rear side by the rolling stand or the pinch roll of the front side; and compression stress (below the yield stress at the rolling time) is produced in that part of the workpiece which is located between the rolling stand or pinch roll at the front side and the rolling stand by the feeding of the workpiece, to assist biting the workpiece between the workrolls of the rolling stand of the rear side. The peripheral speed of the rolls of the workrolls/and or the pinch roll is adjusted after the tip portion of the workpiece is completely bitten between the workrolls of the rolling stand of the rear side while the workrolls remain with the previously set roll gap, and rolling is continued in the condition where the stress of the direction along the rolling line between the rolling stand or pinch roll of the front side is removed. The workpiece can thus be rolled with the high reduction of area which cannot be achieved by conventional regular rolling mills.