| 摘要 |
PURPOSE:To make the wall thickness of a steel pipe uniform especially at its end part by controlling a rooling tension to a specific one in finish-rolling a hollow blank pipe into a steel pipe by a mandrel mill, etc. CONSTITUTION:A hollow blank pipe 5 pierced by a piercer is rolled into a finished pipe by the roll stands 1-3 and mandrel bar 4 of a mandrel mill. The electric currents, voltages, and number of revolutions of motors 9-11 for roll driving, detected by a speed control device 12 during rolling, and the rolling loads of respective roll stands 1-3 detected by rolling load detectors 6-8, are inputted to a pipe-tension control device 13 respectively. The deviation of control speed is calculated, by detecting that the front end of pipe 5 is bitten by the roll stand 1, and basing on the rolling torque, reference torque, tension between the roll stands 1, 2, speed of mandrel bar 4, tension of bar at a pivot stand, and pipe tension between the stands 1, 2, all of which are obtained at the time of said biting; then the wall thickness of pipe-end part of a finished pipe is controlled to a prescribed value by controlling the pipe tension to a target value to improve the yield of finished pipe. |
