RING ROLLING MILL

PURPOSE:To decrease the friction caused by a peripheral speed difference, and to prevent a distortion and a torsion from being generated in a ring materiel, by dividing main roller and a rolling surface constituting member of a mandrel into plural parts in the axial direction in accordance with an average outside diameter of the rolling surface, so that the relative rotation can be executed. CONSTITUTION:When rolling is executed by inserting and holding a ring material R between a main roller 10 and a mandrel 11, the ring material R is rotated in the peripheral direction by a sleeve middle body 15 fixed to a center body 10A of the main roller. Subsequently, each of a sleeve upper body 16 and its lower body 12 coincides with a peripheral speed of the abutting surface of the ring material R and rotates at a speed being different from that of the sleeve middle body 15. Also, in the mandrel 11, as well, each of a sleeve upper body 31 and its lower body 30 coincides with a peripheral speed of the abutting surface of the ring material R and rotates. Therefore, friction due to a peripheral speed difference is not generated between the rolling surface of each part and the surface of the ring material R, and distortion and torsion caused by frictional force generated in the ring material R, can be prevented.