| 摘要 |
PROBLEM TO BE SOLVED: To provide a seamless steel pipe which is excellent in inner surface quality and also good in dimensional accuracy by using a retained type mandrel mill. SOLUTION: A pipe stock is rolled by using the retained type mandrel mill to which a plurality of roll stands are provided in a manufacturing method for the seamless steel pipe. The speed of a mandrel inserted to the pipe stock is kept constant until the rolling of the pipe stock is completed at a first stand of the roll stands. After that, the speed of the mandrel is accelerated. It is preferable that the accelerated speed of the mandrel is controlled so as to become almost equal to the speed of the pipe stock passing through the final stand at the time of completing the rolling at the final stand in order to realize the further improvement of the inner surface quality in the manufacturing method for the seamless steel pipe. COPYRIGHT: (C)2005,JPO&NCIPI
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