CONTROLLING METHOD OF PIPE ROLLING MILL

PURPOSE:To equalize the outside diameter of a pipe, by adjusting a screwdown position of the roll in accordance with the extent of correction of each screw-down position decided by a deviation of the outside diameter derived from a detection value of the outside diameter of the delivery of each rolling mill, and the influenced extent of correction derived by a prescribed method, when controlling the titled control. CONSTITUTION:When controlling a pipe rolling mill of a rolled material 1, on which rollers 21-2n and 31-3n have been placed on (n) stages, respectively, and also in the different directions alternately, the outside diameter of the rolled material 1 in the screw-down direction is detected by outside diameter detectors 5, 6 provided on the delivery, respectively, its outputs D1, D2 are sent to outside diameter deviation operators 400, 500, the respective outside diamter deviations DELTAD1, DELTAD2 are derived, they are inputted to correction extent operators 600, 700 and an influence coefficient operator 800, the operators 600, 700 operate screw-down correction extents DELTADa, DELTADb in accordance with expressionsI, II, and distribute them to each rolling mill through screw-down position adjusting devices 71-7n, etc. In this way, the outside diamter of a pipe is controlled to a target value. This method is suitable for automation, by which a pipe having an equal quality is produced.