JPS5870905A - Expanding method for pipe - Google Patents

Abstract

PURPOSE:To expand pipes at a large expanding rate in the stage of expanding rolling of metallic pipes by skew rolling mills by applying axial pushing forces to the pipe from the inlet side of the rolling mills. CONSTITUTION:A blank pipe Si is forced into the pass line formed of circular conical rolls 21 and a plug 22 at the preceding end of a mandrel by pushing force P0 to expand the pipe. Axial compressive stress components are increased upon the pipe Si in the rolling region to increase the metallic flow in the circumferential direction and to increase the outside diameter and wall thickness of the pipe Si, whereby a product pipe S0 is obtained. At this time, the axial compressive stress from the rear side upon the pipe S0 is increased further by the application of the pushing back force P1 upon the pipe S0 after the expanding, whereby the increase in the outside diameter and the wall thickness is accelerated. Thus the expanding rolling is accomplished at about 2.5-5.0 expanding ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining a metal tube with a large outer diameter from a hollow shell tube.

For example, as a tube expansion technique for increasing the outer diameter of a metal tube such as a steel tube, the following tube expansion method is conventionally known.

FIG. 1 shows a Mannesmann Piercer type inclined rolling mill called an elongator. In this rolling mill,
The raw pipe Sik, its rotation axis intersects the pipe axis on a plane,
The diameter of the product is expanded by passing it through a bath consisting of a pair of barrel-shaped rolls 1 that are set to have a predetermined gap between the rolls and are driven to rotate, and a plug 2 that is fixed to the tip of a mandrel 2-1. A tube SO is obtained. However, in a rolling mill using such barrel rolls, a very large tube expansion ratio (outer diameter of product tube/outer diameter of base tube) cannot be achieved, and is at most about 1.2 to 1.4.

This tube expanding rolling mill, which shows a rotary expander in FIG. 2, has a conical roll 11 that is rotationally driven, and allows the blank tube S1 to pass through a path formed by this conical roll and a plug 12. As a result, a product pipe So with an enlarged diameter is obtained. According to this method, pipe expansion is possible at a pipe expansion ratio of about 1.5 to 20.

Techniques other than the above-mentioned conventional tube expansion method using inclined rolls include a method using a Reckner rolling mill. This is a method in which rolls are placed inside and outside the tube to perform rolling. In this method, rolls must be placed inside the raw pipe, so the inner diameter of the raw pipe must be sufficiently large, and it is a technique that can only be implemented when making a large diameter raw pipe even larger. be. In addition, in this technique, rolls are placed inside the raw pipe, so the length of the raw pipe cannot be made very large.

This invention is applicable to the conventional inclined rolling mill mentioned above.

A method that enables pipe expansion at a pipe expansion rate that far exceeds the pipe expansion rate that can be achieved using conventional pipe expansion technology.

This was done for the purpose of obtaining equipment.

This invention is intended for pipe expansion rolling in which the outside diameter and wall thickness of a blank pipe are changed by a pass composed of a plug and an inclined roll, such as in a rotary expander. Tube expansion rolling using a Retzner rolling mill is not covered.

The present invention will be explained in detail below.

FIGS. 3(a) and 3(b) show one embodiment of this invention. In FIG. 3, 21 is a conical roll,
It has at least two conical surfaces that come into contact with two surfaces of the raw tube Si and the outer peripheral surface of the tube during the tube expansion process.

n is a plug, and its conical outer peripheral surface and the conical roll 21 constitute a tube expansion path. Si is bare pipe, SO
is the product pipe after expansion.

FIG. 3(b) is a longitudinal cross-sectional view showing the process in which the blank tube 8i is expanded by the above-described pass. Figure 3(b)
In this case, the tube is a guide shoe that guides and restrains the outer circumferential surface of the tube during the tube expansion process.

In this invention, although not shown in FIG. 3, a tube pushing means is provided which generates an axial compressive stress in the tube Si before passing, which is constituted by the conical roll 21 and the plug 22. As the means for pushing the raw tube, for example, a pusher using a cold body pressure mechanism or a type such as a pinch roll that applies a thrust to the raw tube by utilizing the friction between the raw tube and the Si outer circumferential surface can be used.

Furthermore, in order to further enhance the effects of the present invention, in a preferred embodiment, means is provided for applying an axial push-back force P1 from the rear to the expanded pipe SO.

As a means for applying the push-back force P1 to the tube, for example, as shown in FIG. 4, the relative relationship between the axial speed of the expanded tube So and the axial speed of the seven-lunged mandrel is controlled using a seven-lunged mandrel. Therefore, a means can be adopted to generate an axial compressive force in the expanded pipe SO.

With the device configured in this way, by applying a pushing force to the raw SiK tube during the tube expansion process, the axial compressive stress component increases on the tube in the rolling area by the nozzle formed by the conical roll 21 and the plug 22, As a result, the metal 70- is increased in the circumferential direction, and the outer diameter and wall thickness of the rolled tube are increased.

Furthermore, in addition to the application of the pushing force PO to the raw pipe Si during the pipe expansion process, the application of the push back force P to the pipe So after the pipe expansion further increases the axial compressive stress on the pipe from the rear. , the outer diameter and wall thickness are noticeably increased.

By the tube expansion technology using the inclined roll rolling machine of the present invention configured as described above, it is possible to expand the tube at a tube expansion rate of 2.5 to 5.0, which far exceeds the tube expansion rate level of 1.5 to 20 by the conventional technology. Rolling becomes possible.

Fig. 4 shows the case in which a pushing force Po is applied to the raw pipe Si at the entrance side of the pass and a push-back force P is applied to the expanded pipe So from the rear of the exit side of the pass during the pipe expansion process using inclined rolls. An embodiment is shown.

In FIG. 4, 31 is an inclined roll, 32 is a plug, 3
2-1 Hammandrel with plug 32 at its tip
is fixed. The push-back mandrel is a push-back mandrel, and has seven lunges at one end, and is loosely fitted into the mandrel 32-1.

A pushing force Po is applied to the expanded tube Si through the path formed by the tilt fAO-ru 31 and the 7 lugs 32, and the 7 langes of the push-back mandrel 34 are brought into contact with the end of the expanded tube SO. At least, by setting the speed V1M of the pushing-back mandrel 34 in the rolling direction (axial direction) lower than the axial speed VISo of the pipe SO after the pipe expansion, it is possible to push back the pipe SO after the pipe expansion. A force acts, creating an axial compressive stress in the tube. The smaller +M/V and So, the larger the push-back force becomes, and the outer diameter of the tube after expansion,
The wall thickness can be increased.

FIGS. 5(a) and 5(b) show another implementation of the present invention.

In FIGS. 5(a) and 5(b), 41 is an inclined roll;
42 is a plug, and 42-1 is a mandrel, on which the plug 42 is fixedly installed. 44 is a pinch roll, which is composed of a pair of rolls having a semicircular caliber.

When a pushing force Po is applied to the raw pipe Si on the bus entry side of the pipe that is being expanded by the bus composed of the inclined rolls 41 and the plugs 42, the axial velocity of the pipe SO after expansion ■1so and the pinch roll 44, the pushing back force acting on the expanded pipe So increases, and therefore,
The outer diameter and wall thickness of the expanded tube So can be increased. Moreover, the pinch rolls 44 are set to idle rotation, and the larger the reduction amount of the pinch rolls 44 is, the larger the push-back force acting on the expanded pipe So becomes.

FIGS. 6(a) and 6(b) show still another embodiment of the present invention. In FIG. 6, 51 is an inclined roll, 52 is a plug, and 54 is a barrel-shaped roll, which are arranged so that their rotation axes intersect with the tube axis on a plane.

In this embodiment, a pushing force Pof is applied to the blank pipe Si at the front stage of the bus, which is constituted by the inclined roll 51 and the plug 52.
By controlling the rotational speed of the barrel roll 54, it is possible to apply a force P to push back the expanded pipe SOK. That is, the rotational speed V of the pipe So after pipe expansion
By applying a brake to Is′o, the axial pushback force P
sk is applied.

To explain this in more detail, as shown in FIG. 6(b), the axial velocity of the tube So after expansion is Vlso, the circumferential velocity is VIs'o, and the tube axial velocity component of the barrel-shaped pinch roll 54 is k vI M , the circumferential velocity component is V, M'
Then %Vt9y', "M/Vt5O?J%
S<Sulfoto, +SO It is possible to increase the push-back force P1 acting on the expanded tube S6, and it is possible to increase the outer diameter and wall thickness of the expanded tube So.

FIG. 7 shows still another embodiment of the invention.

In FIG. 7, 61 is an inclined roll and 62 is a plug. In this embodiment, although the pushing force Po is applied to the raw tube Si at the front stage of the pass, which is the same as in the other embodiments, a special device for generating a push back force to the tube So after tube expansion is used. Not provided. Applying a push-back force P to the tube is done by means of an inclined roll 61. That is,
By modifying the shape of the inclined rolls 61, a push-back force acting on the tube is generated inside the rolling region.

As shown in FIG. 6, if the tube radius at the rolling start point of the tube in the rolling region is rB, the inclined roll radius is rR%, the tube radius at the rolling end point is Rs, and the inclined roll radius is RR, then, The most natural rolling tends to occur since the rotational speed of the tube at the start and end points of the rolling zone are approximately equal.

If this is the case, the closer the tube goes to the exit side of the rolling region, the more it will be subjected to forces that try to reduce the rotational speed and forces that try to prevent the tube from moving forward. In other words, since the degree of increase in roll diameter is smaller than the increase in pipe diameter on the exit side of the rolling region compared to the increase in pipe diameter on the exit side, brakes are applied to deformation when the rotational speed on the exit side of the pipe is smaller than the rotational speed on the entrance side. As a result, the outer diameter and wall thickness increase in the same way as when an axial pushback force is applied.

In the embodiments of this invention described above, the wall thickness level of the pipe is
Since the thickness of the pipe after processing can be determined by the amount of reduction in the pass formed by the inclined rolls and plugs, in the end,
The wall thickness after pipe expansion can be made arbitrarily, and the pipe can be expanded at a pipe expansion rate that far exceeds the level achieved by conventional techniques.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a conventional pipe expansion method, and FIGS. 3, 4, 5, 6, and 7 are diagrams showing a pipe expansion method for this EAK pipe. 1, 11.21.31.41.51.61; Inclined roll 2, 12.22.32.42.52.62; Plug 13.23; Guide shoe style; Mandrel for pushing back 44; Pinch roll for pushing back 54; Barrel-shaped roll for pushing back Si; Raw pipe SO; Product pipe PO; Pushing force P, ; Pushing back force Patent applicant Representative patent attorney Tomoyuki Yabuki (and 1 other person) Figure 1 Figure 2 11211

Claims (1)

[Claims] (]) When expanding a metal tube using an inclined rolling mill such as a rotary expander or an elongator, an axial pushing force is applied to the tube from the entrance side of the rolling mill to obtain a large expansion ratio. A pipe expansion method characterized by the following. (2) When expanding a metal tube using an inclined rolling mill such as a rotary expander or an elongator, an axial pushing force is applied to the tube from the rolling mill entry side, and an axial pushing force is applied to the tube from the rear at the rolling mill exit side. A pipe expansion method characterized by obtaining a large expansion rate by applying pushback force. (3) When expanding a metal tube using an inclined rolling mill such as a rotary expander or an elongator, an axial pushing force is applied to the tube from the rolling mill input side, and a circumferential direction of the tube is applied to the tube from the rolling mill exit side. A pipe expansion method characterized by obtaining a large expansion ratio by suppressing rotation.