JPS61140308A - Skew rolling method of seamless pipe - Google Patents

Abstract

PURPOSE:To roll smoothly a pipe stock by rolling the pipe stock under the previously set reduction rate of wall-thickness, free from generating a flare at the rear end of pipe stock, in elongating a hollow pipe stock into a seamless pipe by a skew rolling mill consisting of an elongator and a reeler, etc. CONSTITUTION:A hollow pipe stock 36 is rolled by a pair of rolling rolls 21, arranged slantly with respect to the rolling line of a skew rolling mill 20, guide shoes, arranged at both sides of the rolling region formed by the rolls 21, and a plug 34 arranged at the middle of said region. At the time of said rolling; a reduction rate of wall thickness, free from generating a flare at the rear end of pipe stock 36, is previously set to roll the rear end of pipe 36 under said reduction rate of wall thickness. That is, the position of plug 34 with respect to the rear end of pipe stock 36 is retreated in order to prevent the generation of the flare of rear end while securing the whole dimensions of the pipe stock 36 at the outlet side, or the reduction rate of thickness at the rear end is set to the value, within a range of being free from generating the flare, by opening the gap between the rolls 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for inclined rolling of seamless pipes suitable for use in inclined rolling mills such as elongators and reelers.

[Prior art] The manufacturing process for seamless pipes basically consists of a drilling process in which holes are made in the material, a stretching process in which the perforated hollow shell tube is stretched to reduce crystallization, and a stretching process in which the hollow shell tube that has been drawn and rolled is rolled. It consists of three steps: finish rolling to reduce the diameter to a predetermined diameter.

FIG. 5 to FIG. 7 are explanatory diagrams showing the elongation rolling process in the manufacturing process of the seamless pipe.

IA, IB are rolling rolls, rolling rolls IA, IB
are arranged so that their rotation axes are inclined at an inclination angle α in opposite directions with respect to the rolling pass line through which the hollow rolled blank tube 2 passes, and are rotatable in the same direction. A pair of fixed shoes 3A, 3B are arranged on both sides of the rolling region sandwiched between these rolling rolls IA, 1B, and are adapted to hold down the hollow shell 2 that bulges out during thinning and stretching rolling. Further, a plug 4 is arranged at the center of the rolling area.

In the above-mentioned inclined rolling mill, the hollow shell 2 enters the rolling area from the direction of arrow F, and the rolling □ roll LA,
When it comes into contact with IB, the hollow tube 2 is rotated forward toward the gorge part where the roll spacing is minimum due to the effect of the inclination angle α, and is contracted, and is connected to the rolling rolls IA, IB and the plug 4.
The pipe will be stretched while being thinned and expanded between the pipes.

Incidentally, the fixed shoes 3A and 3 shown in Fig. 7 are used for the inclined rolling mill.
Instead of B, roller shoes 5A and 5B shown in FIG. 8 are used, or disc shoes 6A shown in FIG. 9 are used.
, 6B has also been proposed. When using the roller shoes 5A, 5B or the disc shoes 6A, 6B, the fixed shoes 3A, 3 are attached to the surface of the tube 2.
No surface scratches due to sliding contact occur as in the case of using B.

[Problems to be solved by the invention] However, each of the above guide shoes 3A, 3B, 5A,
5B, 6A, and 6B, the rear end of the raw tube 2 is buckled and deformed, producing a flare as shown in Fig. 10 at 7'C. Rolls IA, 1B and guide shoes 3A, 3B, 5A, 5B, 6
There is a risk that the protrusion may protrude outward from between A and 6B, deteriorating the shape of the rear end of the protruding blank tube, or making rolling impossible.

In particular, when using roller shoes 5A and 5B shown in FIG. 8, rolling rolls IA and IB and roller shoes 5A
, 5B becomes large, and the above-mentioned protrusion phenomenon of the rear end portion of the raw tube 2 is likely to occur.

Also, when using the disc shoes 6A and 6B shown in FIG. 9, the disc shoes 6A and 6B are
If the diameter of the tube 6B is small, there will be a portion where the gap between the rolling rolls IA, IB and the disk shoes 6A, 6B becomes large, which tends to cause the above-mentioned protrusion phenomenon of the rear end of the raw tube 2.

Note that the rear end portion of the blank pipe 2 is only restrained by the thinner-walled and expanded portion at the front, and is relatively easily deformed and causes the flare 7, which tends to cause the above-mentioned extrusion phenomenon. On the other hand, the distal end of the raw tube 2 is restrained by the thicker, unexpanded portion farther back, and is less likely to cause the above-mentioned protrusion phenomenon.

An object of the present invention is to perform smooth rolling.

[Means for Solving the Problems J] The present invention provides a method in which a pair of rolling rolls are arranged obliquely with respect to a rolling pass line, a pair of guide shoes are arranged on both sides of a rolling area formed by one rolling roll, and In a seamless pipe inclined rolling method in which a plug is placed in the center of the rolling area and a hollow rolled raw pipe is stretched, a thinning rate that does not cause rear end flare at the rear end of the raw pipe is determined in advance, and the The rear end portion is rolled at the above thickness reduction rate.

[Function] According to the present invention, when rolling the rear end of the raw pipe, the occurrence of rear end flare is eliminated, and the rear end of the raw pipe is rolled outward from between the rolling roll and the guide shoe. It becomes possible to perform smooth rolling without causing any protrusion phenomenon.

[Example] FIG. 1 is a partially cutaway side view showing an example of an inclined rolling mill used in carrying out the present invention.

This inclined rolling mill (Elongator) 20 has an entrance side angle and an exit side angle, and roll rolls 21 arranged at an inclination at a constant advance angle, and an entrance side angle and an exit side angle, It has a roller shoe 22 which is arranged adjacent to the roll 21 and is tilted at a constant inclination angle in a drivable state, and a drive motor 23 which applies a driving force to the roller shoe 22. 24 is a fixed pedestal, 25 is a movable pedestal, and 26 is a support pedestal. The roller shoe 22 is supported by a support base 26, and the support base 26 can be fixed to the movable base 25 by a wedge 28 that is fixed to the movable base 25 by a bolt 27. The movable pedestal 25 is fixed to the fixed pedestal 24 by a lock cylinder 30 while being placed on a tapered pedestal 29 movably provided on the fixed pedestal 24 , and is also fixed to the fixed pedestal 24 by a shoe spacing adjustment motor 31 .
The tapered table 29 can be moved in the shoe spacing adjustment direction by movement of the tapered table 29 as the tapered table 2 rotates.

Further, the drive motor 23 is fixed to the fixed frame 24 and engages with the roller shoe 22 via a universal joint 33, so that the roller shoe 22 can be forcibly driven. In addition, 34
is a plug, 35 is a trough, 36 is a hollow tube, 37 is a cannon, and 38 is a bushing.

According to the inclined rolling mill 20, since the roller shoe 22 is forcibly driven, the roller shoe 22 and the raw tube 3
6, the friction between the roller shoe 22 and the roller shoe 22 is significantly reduced.
The occurrence of cracks and wear can be suppressed, and the quality and properties of the raw pipe 36 can be improved. In addition, by forcibly driving the roller shoes 22 at a speed higher than the circumferential speed of the rolling rolls 21, the roller shoe 36 can be moved even when the tube 36 is thin, especially from the tip to the center of the tube 36. 22 and the rolling roll 21 can be suppressed.

By the way, in the rolling of the raw pipe 36 by the above-mentioned inclined rolling mill 20, the rear end portion of the raw pipe 36 is
Flare similar to that shown in the figure is likely to occur, and this flare occurs when the wall thickness t/outer diameter of the raw pipe 36 is small or
Flare is likely to occur when the wall thinning rate [(inlet side wall thickness - outlet side wall thickness)/inlet side wall thickness] of the blank tube 36 is large, that is, the occurrence of flare at the rear end of the blank tube 36 is likely to occur when the wall thickness of the blank tube 36 is large. Base pipe 36
As shown in FIG. 3, it depends on the rate of thinning of the raw pipe 36. That is, there is a boundary between the wall thickness reduction rate and the presence or absence of flare, and the greater the wall thickness reduction rate, the thinner the pipe becomes and the more likely it is to expand and cause rear end flare. In addition, FIG. 3 shows the result of rolling a raw pipe of a product outer diameter finch in the above-mentioned inclined rolling mill 20.

Therefore, in the present invention, when rolling the raw pipe 36 by the inclined rolling mill 20, a thinning rate is determined in advance so that no rear end flare occurs at the rear end of the raw pipe 36. The part is rolled at the above thickness reduction rate. That is, in FIG. 2, in order to prevent the occurrence of rear end flare while ensuring the overall dimensions of the exit side raw pipe, the position of the plug 34 relative to the rear end of the raw pipe is moved back, or the position of the plug 34 is By widening the distance between the rolling rolls 21 and the rear end, the thickness reduction rate at the rear end is set within a range where flare does not occur. In addition, in carrying out the present invention, it is preferable to carry out the above-mentioned rear end thinning control within a range of 1 m from the rear end side so as not to adversely affect the rolling properties in the rolling mill in the next step. .

FIG. 4 shows the presence or absence of trailing end flare when rolling is carried out using the inclined rolling mill 20 marked E to set the wall thickness of the inlet tube to 23 mm+ and the wall thickness of the outlet tube to 15 to 15.5 mm. FIG. The broken line is the rolling result using the conventional method.
A flare occurred. On the other hand, the solid line shows that the gorge (roll spacing) of both rolling rolls 21 is moved at 2.28 am/sec with respect to the rear end of the raw tube, and the thickness reduction rate at the rear end of the raw tube is such that no flaring occurs. The tip of the raw pipe
Even though the thickness of the center part was thinner than in the case of the broken line, there was no flaring and smooth rolling was possible. The present invention is applicable not only to the case where such a roller shoe is used, but also to an inclined rolling mill using a fixed shoe shown in FIG. 7 and a disc shoe shown in FIG. 9.

[Effects of the Invention] As described above, the present invention includes a pair of rolling rolls arranged at an angle with respect to a rolling pass line, a pair of guide shoes arranged on both sides of a rolling area formed by one rolling roll, and In a seamless pipe inclined rolling method in which a plug is placed in the center of the rolling area and a hollow rolled raw pipe is stretched, a wall thinning rate that does not cause rear end flare at the rear end of the raw pipe is determined in advance, and the The rear end of the tube is rolled at the above thickness reduction rate. Therefore, it is possible to eliminate the occurrence of rear end flare and to perform smooth rolling.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of an example of an inclined rolling mill used in carrying out the present invention, FIG. 2 is a cross-sectional view of essential parts showing the state of rolling by the inclined rolling mill, and FIG. A diagram showing the relationship between the thinning rate and the presence or absence of trailing end flare, FIG. 4 is a diagram showing the effects of the present invention, and FIG. 5 is a plan view showing the state of rolling by a general inclined rolling mill. Figure 6 is a side view of Figure 5;
Fig. 7 is a front view of Fig. 5, Fig. 8 is a front view showing a rolling state using a roller shoe, Fig. 9 is a sectional view showing a rolling state using a disc shoe, and Fig. 1O is a rear end flare. FIG. 2 is a perspective view showing a state in which 20... inclined rolling mill, 21... pressure roll, 22
...a-Cheeshu, 34...Plug, 36...
Hollow plain pipe / Agent Osamu Shiokawa Fig. 2 Fig. 5 Fig. 6 Fig. 3 Wall thickness of S plain pipe (z%)

Claims (3)

[Claims] (1) A pair of rolling rolls are arranged at an angle with respect to the rolling pass line, a pair of guide shoes are arranged on both sides of the rolling area formed by both rolling rolls, and a plug is arranged in the center of the rolling area, and a hollow In the inclined rolling method for seamless pipes in which a rolled raw pipe is stretched, a thickness reduction rate that does not cause rear end flare at the rear end of the raw pipe is determined in advance, and the rear end of the raw pipe is rolled at the above thickness reduction rate. A method for inclined rolling of seamless pipes. (2) The method for inclined rolling of a seamless pipe according to claim 1, in which rolling is performed at the above-mentioned thickness reduction rate by retracting the plug position toward the rolling exit side with respect to the rear end of the raw pipe. . (3) The rear end of the raw pipe is rolled at the above thickness reduction rate by widening the distance between both rolling rolls.
The method for inclined rolling of seamless pipes described in Section 1.