JPH0569012A - Method for rolling tube stock - Google Patents

Abstract

(57) [Summary] [Object] To provide a shell rolling method capable of preventing defective biting without causing any inconvenience in rolling by a plug mill. [Structure] After the tip of the raw tube 3 is engaged with the rolls 1, 1,
The interval between the rolls 1 and 1 is narrowed and the plug 2 is retracted toward the exit side of the rolls 1 and 1, and after the blank tube 3 has slipped out, the interval between the rolls 1 and 1 is expanded to advance the plug 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shell rolling method, and more particularly to a shell rolling method using an elongator.

[0002]

2. Description of the Related Art FIG. 4 is a side view showing an outline of an elongator as an inclined rolling mill, in which 1 and 1 are rolls. The rolls 1, 1 are barrel-shaped and are arranged with their curved surfaces facing each other. The raw tube 3 is caught between the rolls 1 and 1,
Inside of it, a conical plug 2 from the exit side of the rolls 1 and 1
Is inserted and rolled. A core metal 2a is connected to the plug 2 so that the plug 2 can be moved forward and backward by the core metal 2a.

[0003]

In the rolling by the elongator, a biting failure sometimes occurs when the raw tube 3 is bitten. Conventionally, by shortening the distance from where the outer surface of the raw pipe 3 hits the roll 1 to where the inner surface of the raw pipe 3 hits the plug 2 (hereinafter referred to as the hollow chamfer length), it is possible to prevent biting failure of the raw pipe. Is known, and a method of narrowing the gap between the rolls 1, 1 which has been expanded before the biting of the raw pipe 3 after the biting, and a plug 2 which has been advanced to the entrance side of the rolls 1, 1 in advance. The method of retracting after being bitten was adopted. However, in the former method, the wall thickness of the tip portion of the raw pipe 3 becomes thicker, which may cause defective biting in the plug mill in the next step. In the latter method, the wall thickness of the tip portion of the raw pipe 3 becomes thin. Therefore, in the plug mill in the next step, a thin wall defect may occur.

The present invention has been made in view of the above circumstances, in which the gap between the rolls is narrowed after the raw pipes are bitten, the plug is retracted to the exit side of the rolls, and the gap between the rolls is widened after the raw pipes are slipped out. An object of the present invention is to provide a shell rolling method capable of preventing defective biting without causing any inconvenience in rolling by a plug mill in the next step by advancing the plug.

[0005]

In the method for rolling a raw pipe according to the present invention, the raw pipe is caught between a pair of rolls, and a plug is inserted into the raw pipe from the exit side of the rolls to form the raw pipe. In the method for rolling a raw pipe, the tip of the raw pipe is bitten into the roll, the gap between the rolls is narrowed, the plug is retracted to the exit side of the roll, and the roll is pulled out of the raw pipe. It is characterized in that the plug is advanced with the interval between the two expanded.

[0006]

In the present invention, the gap between the rolls is expanded and the plug is advanced toward the roll entry side before the blank tube is bitten. Therefore, the empty length is further shortened as compared with the conventional method of preventing biting failure. Therefore, it is possible to effectively prevent a defective biting of the raw tube. Since the interval between the rolls is narrowed after the raw pipe is bitten and the plug is retracted to the exit side of the roll, the wall thickness variation of the raw pipe is suppressed and the wall thickness of the raw pipe is appropriately adjusted. The thickness can be maintained, and biting defects and thin wall defects do not occur during rolling in the plug mill in the next step.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a side view showing an outline of an elongator according to the present invention, in which 1,1 are rolls. The rolls 1, 1 are barrel-shaped and are arranged with their curved surfaces facing each other. The raw tube 3 is caught between the rolls 1 and 1,
Inside of it, a conical plug 2 from the exit side of the rolls 1 and 1
Is inserted and rolled. A core metal 2a is connected to the plug 2 so that the plug 2 can be moved forward and backward by the core metal 2a.

In the present invention, the gap between the rolls 1 and 1 is expanded in advance before the raw pipe 3 is bitten, and the plug 2 is advanced to the inlet side of the rolls 1 and 1. After the raw pipe 3 is bitten, the roll 1 is rolled. ，
The interval of 1 is narrowed and the plug 2 is retracted to the exit side of the rolls 1 and 1 in synchronization with each other. Then, after the blank pipe 3 has slipped out, the gap between the rolls 1 and 1 is expanded and the plug 2 is advanced to the entrance side of the rolls 1 and 1.

FIG. 2 is a change diagram of the interval between the rolls 1 and 1, with the horizontal axis representing time and the vertical axis representing the interval between rolls 1 and 1. t ₁ is the time when the tip of the raw tube 3 is bitten,
t ₃ is the time when the base tube 3 slips out. Timings t ₁ and t ₃ are obtained by an electric control circuit such as a tube detector and a load relay provided on the entrance side of the rolls 1, 1. H
₁ is an interval between the rolls 1 and 1 required for rolling the raw tube 3, and H ₂ is larger than H ₁ by 3 to 4 mm. Rolls 1 and _{1 are} separated from each other at intervals of t ₁ to t ₂ and t ₃ to t ₄ from H ₂ to H.
Rapid change from ₁ to H ₁ to H ₂ .

FIG. 3 is a change diagram of the position of the plug 2.
The horizontal axis represents time, and the vertical axis represents lead size. The lead size represents the relative position of the tip surface of the plug 2 with respect to the center surface of the roll 1 below the raw tube 3. Time t ₁ ,
t ₂ and t ₃ are equal to the times t ₁ , t ₂ and t ₃ in the change diagram of FIG. L ₁ is a lead size required when rolling the raw tube 3, and L ₂ is longer than L ₁ by 30 to 40 mm. The position of the plug 2 is changed from L ₂ to L ₁ during the time of t ₁ to t ₂ and t ₃ to t _4.
, L ₁ to L ₂ rapidly.

[0011] If after inclusive engage the base pipe 3 to tune the movement of the plug 2 to the movement of the rolls 1, 1 in order to suppress the thickness variation of the mother tube 3 in t ₁ ~t ₂ times. At this time, the plug 2 is moved backward by moving the core metal 2a by a hydraulic cylinder or the like, and the movement of the rolls 1, 1 is synchronized with the flow control valve of the hydraulic oil of the hydraulic cylinder or the like. In addition, when the blank pipe 3 has passed through the bottom, the timing of the change of the interval between the rolls 1 and 1 and the start of the change of the position of the plug 2 are matched, but the timing of the change end need not be adjusted.

As described above, biting failure can be prevented without causing any inconvenience in the subsequent rolling by the plug mill. In the embodiment of the present invention, the case where the elongator is applied as the inclined rolling mill is described, but the invention is not limited to this.

[0013]

As described above, according to the present invention, the gap between the rolls is narrowed after the raw pipes are engaged, and the plug is retracted to the exit side of the rolls. Therefore, the present invention has excellent effects such as preventing biting failure without causing any inconvenience in rolling by the plug mill in the next step.

[Brief description of drawings]

FIG. 1 is a side view showing an outline of an elongator according to the present invention.

FIG. 2 is a change diagram of roll intervals.

FIG. 3 is a change diagram of a position of a plug.

FIG. 4 is a side view showing an outline of an elongator.

[Explanation of symbols]

 1 roll 2 plug 2a core metal 3 element tube

Claims (1)

[Claims] 1. A raw material pipe rolling method in which a raw pipe is caught between a pair of rolls, a plug is inserted into the raw pipe from the outlet side of the rolls, and the raw pipe is rolled. After engaging with the roll, the gap between the rolls is narrowed to retract the plug toward the exit side of the roll, and the gap between the rolls is widened after the plug is pulled out to advance the plug. A method for rolling a tube.