PURPOSE: To obtain a steel pipe of the outside diameter conforming exactly to the target stably by presuming the pattern of the wall thickness of the shell on reeler mill inlet side beforehand, determining the target wall thickness of the shell after rolling in such a way that the rate of wall thickness reduction equals to the rate of prescribed expansion of outside diameter, and controlling a roll gap in accordance with this.
CONSTITUTION: The temp. on the inlet side of a shell by a reeler mill inlet side thermometer 20, the outside diameter on the outlet side of the shell by a reeler mill outlet side outside diameter gage 27, the rolling load by a load cell 28, and, besides, the rolling reduction from a screw-down position meter 24 detecting a roll gap are inputted to a control arithmetic device 21. In accordance with this, it outputs a screw down control signal to a screw down control device 23, thereby performing the position controlling of rolling rolls 10, 10' via a screw-down device 18, and a screw down screw 17. It is possible to forecast the rolling load durning rolling of the reeler mill from the shell inlet side temp. by the thermometer 20. In the determination of the inlet side shell wall thickness pattern, the patterns with respect to the various points in the longitudinal direction of the absolute wall thickness of the shell after the plug mill are obtained with the data from the rolling load of the plug mill and the length meter.
OKAZAKI SHIYUUJI
SAKURADA KAZUYUKI
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