To absorb the fluctuation of a rolling load at the time of an abnormal rolling in manufacturing a seamless steel tube, and to simply repair the equipment of the rolling mill.
On the rolling down device of this rolling mill, hydraulic cylinder 11 into which working liquid 13 has been injected, hydraulic cylinder rod 12 and rolling down screw 10 to be rotated by a motor-driven screw jack 9, are provided. The hydraulic cylinder 11 is mounted on a rolling mill stand 7, a detent is provided on the hydraulic cylinder rod 12 and on the inside surface of the hydraulic cylinder rod 12, an internal thread surface engaging with an external thread surface worked on the outside surface of the rolling down screw 10, is provided. With the rotation of the rolling down screw 10, rolling rolls 3 held at the tip of the rolling down screw 10, are elevated and lowered. This is the rolling down method using this rolling down device. During rolling, the rolling rolls are rolled down by a rotation in the lowering direction of the rolling down screw, and an excessive rolling load is absorbed by the working fluid injected into the hydraulic cylinder. At the time of an abnormal rolling, the hydraulic cylinder is retracted, and a gap is immediately provided between a material to be rolled and the rolling roll.
YOKOI YOICHI
KIYOOKA EIJI
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