A bias rolling machine, a method for manufacturing a seamless tube shell, and a method for manufacturing a seamless steel tube

Abstract

A bias rolling apparatus is provided herein for preventing form defects in non-constant portions of the front and rear ends of a seamless tube shell. The bias rolling apparatus includes: a bias punch rolling mill for punch rolling; and a bias outside diameter rolling mill after the bias punch rolling mill, the bias rolling apparatus satisfying the following formulas (1) and (2): 3 × (1.2PO + 2G) = LS = 0.8BL ... (1) 1.2PO + 2G > DS = DB + 2G ...(2), where LS is the distance (mm) between a punch rolling roll zone and an outside diameter rolling roll zone, DS is the gap between the outside diameter rolling rolls, PO is the outside diameter (mm) of a plunger, G is the gap (mm) between the plunger and the punch rolling rolls, BL is the length (mm) of a bar, and DB is the outside diameter (mm) of the bar.

Claims

1. A bias rolling apparatus, characterized in that it comprises: a bias perforation rolling mill for perforation rolling; and a bias outside diameter rolling mill after the bias perforation rolling mill, the bias perforation rolling mill having a plurality of perforation rolling rolls provided circumferentially around a pitch line, a plunger provided between the plurality of perforation rolls, and a bar supporting the plunger, the bias outside diameter rolling mill having a plurality of outside diameter rolling rolls provided circumferentially around the pitch line, the bias rolling apparatus satisfies the following formulas (1) and (2), 3 x (1.2PO + 2G) < LS < 0.8BL (1) 1.2PO + 2G > DS > DB + 2G (2), where LS is the distance (mm) between a rolling zone of the punch rolling rolls and a rolling zone of the external diameter rolling rolls, DS is the space between rolls between the plurality of external diameter rolling rolls, PO is the external diameter (mm) of the plunger, G is the space (mm) between the plunger and the punch rolling rolls, BL is the length (mm) of the bar, and DB is the external diameter (mm) of the bar.

2. The bias rolling apparatus according to claim 1, further characterized in that the bias perforation rolling mill has three or more perforation rolling rollers.

3. The bias rolling apparatus according to claim 1 or 2, further characterized in that the bias outer diameter rolling mill has three or more outer diameter rolling rollers.

4. The skew rolling apparatus according to any of claims 1 to 3, further characterized in that the skew outer diameter rolling mill additionally includes a drive unit for varying the distance between rollers DS, and a sensor for detecting a position of a seamless tube housing.

5. The bias rolling apparatus according to any of claims 1 to 4, further characterized in that the bias outer diameter rolling mill additionally includes a drive unit for rotaryly driving the outer diameter rolling rollers.

6. A method for manufacturing a seamless tube shell with the bias rolling apparatus according to any of claims 1 to 5, characterized in that the outer diameter rolling rolls have an inter-roll spacing DS which is 84% ​​to 99% of an outer diameter dÜ2 of a constant portion of a seamless tube shell after punch rolling.

7. The method for manufacturing a seamless tube shell using the bias rolling apparatus according to claim 5, further characterized in that the outer diameter rolling by the bias outer diameter rolling machine is faster than the perforation rolling by the bias perforation rolling machine.

8. A method for manufacturing a seamless steel tube, characterized in that it comprises: punching a steel material into a seamless tube shell with the bias rolling apparatus according to any of claims 1 to 5; and hot rolling the seamless tube shell.

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