PURPOSE: To enable control so as to obtain a target pipe outside diameter by determining the set change rate of a pipe surface temp. in accordance with specific equation from the error in the outside diameter of the pipe calculated from the measured value of the outside diameter of the pipe after rolling of a preceding material and changing the pipe surface temp. prior to rolling of the next material.
CONSTITUTION: An arithmetic control circuit 44 in high bulging and rolling of the seamless pipe calculates the error ≥Do in the outside diameter of the pipe from the measured value Di of the outside diameter of the pipe after rolling by a pipe outside diameter measuring instrument 43 and calculates the set change rate ≥θ of the pipe surface temp. by the specific equation. Further, the pipe surface temp. prior to rolling of the next material on the inlet side of rolling rolls 32A, 31B is changed by the set change rate ≥θ of the pipe surface temp. The arithmetic control circuit 44 drives a high-frequency induction heater 41 by a heating controller 41A in the case of heating up the pipe surface temp. The arithmetic control circuit 44 controls a motor M of a blank pipe transporting device 42 in such a manner that the material to be rolled is temporarily stopped or decelerated by a transporting speed controller 42A in the case of lowering of the pipe surface temp. As a result, the target pipe outside diameter is obtd.
SHIMIZU TETSUO
TOYOOKA TAKAAKI
