| 摘要 |
PURPOSE:To form a pipe material having the wall thickness uniform thoroughly in a circumferential direction by installing two units of stands consisting of 3- roll type caliber rolls so as to drive the stands separately and arranging the caliber rolls by dislocating the rolls at specific angles. CONSTITUTION:Two units of 3-roll type caliber roll stands 7, 8 respectively of an independent driving type are disposed continuously by changing the arrangements by 60 deg. from each other. A plug or mandrel bar 9 is inserted into a blank pipe 4, and the pipe 4 is subjected to reduction drawing between caliber rolls 6 and the plug or mandrel bar 9, whereby a finished pipe 5 is obtained. Since in the 1st stand 7 there is no need for finishing the pipe 4 round, it is sufficient to finish the pipe to a uniform wall thickness in the range of at least about + or -30 deg. from the central part in the caliber groove bottom of each roll, and the pipe 4 is subjected to the rolling reduction corresponding to the roll edge parts in the 1st stand 7, in the central part of the caliber groove bottom of the rolls in the 2nd stand 8. |
