| 摘要 |
PROBLEM TO BE SOLVED: To provide the technique of manufacturing a seamless tube excellent in quality at high productivity. SOLUTION: Piercing and rolling are performed by using a piercing mill provided with inclined rolls under conditions that the reduction ratio TDFT at the tip of a plug is≤0.04, or the square root of the product of the TDFT and the number N of rotations of a billet is≤0.4. The positions of the inclined rolls are decided so that the gorge reduction ratio TDFT of the inclined rolls satisfies the following formula (1). The piercing and rolling is performed by using the plug having a shape which satisfies the following formula (2). In at least the unsteady region of the piercing and rolling, the billet is pressed with a pusher. (1) -0.01053EL+0.8768≤TDFT≤-0.01765EL+0.9717. (2) -0.95√(TDFT×N)+1.4≤L2/d2≤-1.4√(TDFT×N)+3.15. Here, N=(Ld×EL)/(0.5×π×Bd×tanβ); Ld is the projected contact length from a biting point to the tip of the plug; EL is the piercing ratio;βis the inclined angle of the roll; L2 is the length of the rolling part of the plug; and d2 is the outside diameter in the boundary position between the rolling part and the reeling part of the plug. COPYRIGHT: (C)2008,JPO&INPIT
|
