CONTROLLER FOR PLUG MILL

PURPOSE:To obtain a pipe of high accuracy, by performing set-up control by converting rolling phenomena of a plug mill in a seamless steel pipe manufacturing process into a equation model by measuring a load, a temp., and a dimension. CONSTITUTION:A controlling device of a plug mill 12 consists of devices 41-43, 46, and 51-53 and stores a equation model and a outer dia. D2, a wall thickness t2 after 2-pass rolling. A wall thickness t0 is calculated by the device 41 from the hollow blank pipe weight W0 measured by a measuring device 54 at the inlet side of an elongator 21, and the outer dia. D0 and the length l0 of a blank pipe before rolling by a mill 12 measured by measuring devices 23, 24. The temp. TP of the blank pipe in rolling is calculated by the device 42 from the wall thickness t0 and the blank pipe temp. TE of a measuring device 25. The study controller 53 outputs a correcting coefficient Z of the equation model to the device 43 by the outputs of the devices 41, 42, and here, it predicts a totaled rolling load of 1 and 2 passes to detemine a screw-down position S1 of the 1 pass and then a screw-down position of the mill 12 is set by the device 46. A screw-down position S'2 of the the 2 pass is determined from actual rolling data at the 1 pass by a set-up device 50. The total load and wall thickness calculating devices 51, 52 output the results to the device 53. The outer dia. D2 and the length l2 of the blank pipe after completion of rolling are measured respectively by measuring devices 28, 29 and are inputted to the device 52.