Abstract: A rolling mill is characterized in that three hydraulic actuators, positid in a mill frame and comprising yokes with attached rolling tools therein, are provided with a piston rod having two pistons. The outer piston co-operates with an external cylinder which is mounted on a body of the actuator by means of a threaded joint. The inner piston co-operates with an internal cylinder attached slidably within said body.At one end, the piston rod is provided with a thrust flange being in contact with spacer washers mounted on the external cylinder, whereas the opposite end of said piston rod includes a stop positioned in a seat of a slider, said stop co-operating with a shoulder on said slider. The slider is mounted slidably on a bottom of the internal cylinder, the end portion of said slider having a pressure flange to press down a tool yoke to the bottom of the internal cylinder during rolling operation.

Abstract: A method and apparatus of forming ribbed pipes, after an initial pipe resssing in which bending of the rib of the plane perpendicular to the rolled pipe axis takes place, and straightening of the rib thenafter. Then on duplex metal pipes, the outside pipe is additionally compressed to the core pipe.A tool for performing the aforementioned is equipped with a disk section for bending the rib, it is formed of a thrust disk and a straightening disk. When rolling a duplex metal pipe at least one compressing disk is placed therebetween.