JPH09314244A - Method and device for manufacturing tapered metal tube - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a method for manufacturing a tapered metal pipe that expands with a fluid pressure while monitoring the deformation state of a raw pipe during processing work, and an apparatus for carrying out the method. I am trying. In a method for manufacturing a tapered metal tube, a metal tube is inserted into a mold having a cavity whose diameter is reduced in the longitudinal direction toward an end, and the inside of the tube is expanded by applying a fluid to the tube. As the pressurization progresses, the base pipe is deformed to monitor the restrained state generated between the base pipe and the mold. After making a space between the inner wall of the mold and recovering the free state,
It is characterized in that the pressurization is restarted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called tapered metal pipe manufacturing method and device, and more particularly, to inserting a raw pipe into a mold having a cavity whose diameter in the longitudinal direction becomes smaller toward the end. The present invention relates to a method for expanding a tube by subjecting a raw tube to bulging by hydraulic pressure and an apparatus that can be used for implementing the method.

[0002]

2. Description of the Related Art A steel pipe whose diameter decreases in the longitudinal direction toward one end, that is, a so-called taper steel pipe is less versatile than an ordinary straight pipe, and is therefore in little demand. However, since it is structurally superior to a straight pipe as a self-supporting pillar, the demand for it as a pillar of an illumination lamp on a highway, for example, is increasing.

By the way, as a method of manufacturing such a tapered steel pipe, there is a method of performing bulging by hydraulic pressure (hereinafter referred to as hydraulic bulge). It is disclosed in, for example, JP-A-61-373.
As disclosed in Japanese Unexamined Patent Publication No. 27-27, a straight tubular stock pipe is inserted into a mold having a cavity whose diameters at both ends are smaller than the central portion, and liquid (mainly water) is applied from both shaft ends to the interior of the stock pipe. While simultaneously applying pressure to the both ends of the base pipe by the axial force of the pressure rod, the outer surface of the base pipe is expanded along the cavity wall,
It has a predetermined shape. However, this method has a drawback that buckling deformation and flaws occur in the element pipe because an external force is applied by the pressure rod. Therefore, Japanese Patent Application No. 7-
Japanese Patent Laid-Open No. 191986 proposes a method and an apparatus for manufacturing a tapered steel pipe having excellent quality by simply applying an internal pressure with a fluid.

However, in each of the above-mentioned conventional hydraulic bulge devices, once the raw pipe is set in the mold, the progress of expansion of the raw pipe is completed until the bulge processing is finished and the mold is opened. Because it is not possible to confirm, it is unknown whether smooth and stable deformation is being performed, processing work is performed, and in some cases, the base pipe and the mold become stuck (constrained) and stable deformation There was a problem that the local pipe was broken beyond the limit (thickness limit) and the shell was broken.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a method for manufacturing a tapered metal pipe that expands by fluid pressure while monitoring the deformation state of the raw pipe during processing work, and an apparatus for implementing the method. It is intended to be provided.

[0006]

In order to achieve the above-mentioned object, the inventor diligently studied the causes and countermeasures for forming a non-uniform wall thickness in the pipe cross section which occurs during bulging. In addition, as background information,
As shown in the table below, there was a bulging theory for thin-walled pipes that "when the pipe end is restrained, the maximum expansion ratio of the raw pipe becomes smaller than when the pipe end is free." Then, from the above knowledge and the fact that "the wall thickness deviation increases or the pipe breaks when the movement in the axial direction of the pipe stops during the pressure deformation of the raw pipe", "the movement of the pipe end is detected. The present invention was devised based on the idea that uniform processing can be performed if the pressurization is interrupted before the blank tube and the inner wall of the mold are in a restrained state.

That is, according to the present invention, a metal base pipe is inserted into a mold having a cavity whose diameter is reduced in the longitudinal direction toward the end, and the inside of the base pipe is compressed with a fluid to expand the pipe. In the manufacturing method of 1., the restraint state generated between the shell and the die due to deformation of the raw pipe as the pressurization progresses, and when the restraint condition is reached, the temporary pressurization is suspended. A method for manufacturing a taper metal tube is characterized in that a gap is formed between the base tube and the inner wall of the mold to restore the free state, and then pressurization is restarted. Further, the present invention is to monitor the restrained state between the raw pipe and the die by a pipe end axial movement amount sensor, or to determine the gap between the raw pipe and the inner wall of the die by the end of the raw pipe A method for manufacturing a taper metal pipe, characterized in that the portion is pushed in the longitudinal center direction of the mold and the mold is moved by a reaction force to form the part. Furthermore, the present invention is the method for manufacturing a tapered metal tube, characterized in that the completion of the pressurization is detected by a tube expansion completion sensor. In addition, the present invention provides a pipe end mold including a mold having a cavity whose diameter decreases in the longitudinal direction toward the end and a fluid supply port for pressurizing the inside of the raw pipe inserted in the mold. And a taper metal pipe manufacturing apparatus comprising a pressurizing means for supplying a fluid to the raw pipe through the supply port,
The mold having a cavity whose diameter is reduced is divided into a center mold and a side mold, and the pipe end mold is provided with a pressing means for pushing the end of the raw pipe. In addition to the taper metal pipe manufacturing apparatus, the present invention is also a taper metal tube manufacturing apparatus characterized in that the central mold is divided into two in a direction perpendicular to the axis thereof.

In the present invention, since the method and apparatus for manufacturing the tapered metal pipe utilizing the hydraulic bulge processing are constructed as described above, before the pipe end of the raw pipe is restrained with the mold during the processing. Since the pressurization can be stopped, it is possible to perform bulge processing in an ideal state where the pipe end is always free. as a result,
The theoretical maximum pipe expansion ratio (36%), that is, 3/2 of the uniform elongation (24%) of the raw pipe, enables stable production of taper pipes without uneven thickness. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the apparatus for manufacturing a tapered metal tube according to the present invention, the entire mold is shown in FIG. As a whole, the mold has a mold 13 having a cavity 13 whose diameter is reduced in the longitudinal direction toward the end, and a raw pipe 4 provided at the end of the mold and inserted in the mold. And a tube end mold 1 having a fluid supply port 5 for pressurizing the inside of the. Then, the mold having the cavity is divided in the longitudinal direction into one central mold 3 and two side molds 2 arranged on the side thereof. The point of dividing the die having the tapered cavity in this way is an important point of the present invention. This is because the positions of the blank tube 4 and the side mold 2 are displaced and separated from each other. Due to this displacement, the pipe end mold 1
2 is provided with a pressing means (for example, a hydraulic jack) 6 for pressing the end portion of the raw pipe 4 as shown in FIG.
Further, although not shown, a pressurizing means for supplying a fluid to the base pipe 4 is connected to the fluid supply port 5.

Further, according to the present invention, the pipe axial direction movement amount detecting sensor 10 which also serves as a pipe centering roller is embedded in the pipe end die 1 to monitor the movement of the pipe end of the raw pipe 4. There is. The sensor 10 catches whether or not the movement of the raw tube 4 is stopped or the movement speed is lower than a predetermined value, and the operator judges whether to suspend or continue the pressurization based on the information. Of. In the case of interruption, when the pressing means 6 is actuated and the restraint between the raw tube 4 and the inner wall of the mold is released, the pressurization is restarted again. This operation is not limited to once in the production of one taper metal tube, and may be performed several times until the completion of bulging.

In addition, the present invention avoids excessive pressurization,
In order to stabilize the product quality (including uneven thickness), the tube expansion completion sensor 11 for quickly determining the completion of bulge processing is mainly inserted into the central mold 3 to catch the contact with the raw tube 4. . In addition, the central mold 3 is divided into two in a direction along the axis of the central mold 3 so as to be useful for separating the mold and the blank tube.

[0012]

EXAMPLE A method for manufacturing a tapered metal tube according to the present invention was carried out using the apparatus described above (see FIGS. 1 and 2).
At that time, the taper ratio is 3.6 and the pipe expansion ratio is 3 by joining the side mold 2 and the central mold 3 having the sizes shown in FIG.
A 0% integral mold was assembled. The tube end die and the side die are preliminarily screw-joined.

The size of the used raw pipe (steel pipe) 4 is shown in Table 1.
The mechanical properties are shown in Table 2. Pressurized fluid uses water,
The pressure was applied while monitoring the information of the tube axial direction movement amount detection sensor 10 described above. Water pressure is 210kg / mm ² shown in Table 3.
When it became, it was found from the information of the sensor 10 that the contraction of the tube length had stopped, and the pressurization was stopped. Immediately tube end mold 1
The pressing means 6 provided in the above was operated to move the end portion of the raw pipe 4 to release the constraint between the inner wall of the mold and the raw pipe. Then, the water pressure shown in Table 3 was applied again, and the processing was ended by the instruction of the tube expansion completion sensor 11. Table 4 shows the size of the obtained tapered metal tube.
Shown in

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

Next, during the production of the tapered metal pipe as described above, the pipe expansion ratio and the wall thickness deviation ratio were measured, and the relationship between them was obtained. FIG. 4 shows the results. According to the present invention, when the pipe shaft was manufactured without restraint, the uneven thickness ratio was about 10% even when the pipe expansion ratio was 30%, which was very good. On the other hand, when manufactured without releasing the constraint as in the conventional case, the uneven thickness ratio is extremely large.

The tube expansion rate and the wall thickness deviation rate were calculated based on the following equations. Expansion ratio = ((maximum diameter after expansion-element tube diameter) / (element tube diameter)) x
100 (%) Thickness deviation = ((maximum plate thickness in the circumferential direction-minimum plate thickness) / (maximum plate thickness)) x 100

[0020]

As described above, according to the present invention, it is possible to perform bulge processing in an ideal state while monitoring the deformation of the raw pipe, and to expand the pipe stably up to the theoretically predicted maximum pipe expansion ratio (36%). As a result, it became possible to mass-produce tapered metal tubes with less uneven thickness.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an apparatus for manufacturing a tapered metal tube according to the present invention.

FIG. 2 is a vertical cross-sectional view showing details of the vicinity of the tube end die of FIG.

FIG. 3 is a diagram showing a size of a mold used in an example of the present invention.

FIG. 4 is an example showing an implementation result of the present invention.

[Explanation of symbols]

1 Pipe End Mold 2 Side Mold 3 Central Mold (Vertical Split Type) 4 Element Pipe (Metal Pipe) 5 Supply Port 6 Pressing Means (Hydraulic Jack) 7 Packing (For Jack) 8 Packing (For Material) 9 Sliding part ring 10 Pipe axial movement amount monitoring sensor (also serves as a centering roller) 11 Pipe expansion completion detection sensor 12 Restraint part 13 Cavity

Claims (6)

[Claims] 1. A method for manufacturing a tapered metal tube, wherein a metal tube is inserted into a mold having a cavity whose diameter is reduced in the longitudinal direction toward the end, and the inside of the tube is expanded by being pressurized with a fluid. , As the pressurization progresses, the base pipe is deformed and the restrained state generated between the base pipe and the mold is monitored. A method for manufacturing a taper metal tube, characterized in that a space is formed between the mold and the inner wall of the mold to recover the free state, and then the pressurization is restarted. 2. The method for producing a tapered metal pipe according to claim 1, wherein the restraint state between the raw pipe and the mold is monitored by a pipe end axial movement amount sensor. 3. A gap between the element pipe and the die is formed by pushing an end portion of the element tube toward a longitudinal center of the die and moving the die by a reaction force. The method for manufacturing a tapered metal tube according to claim 1 or 2. 4. The method for manufacturing a tapered metal pipe according to claim 1, wherein the end of the pressurization is detected by a pipe expansion completion sensor. 5. A mold having a cavity whose diameter decreases toward the end in the longitudinal direction, and a pipe end mold provided with a fluid supply port for pressurizing the inside of the raw pipe inserted into the mold. In a taper metal pipe manufacturing apparatus comprising a pressurizing means for supplying a fluid to a raw pipe through the supply port, a mold having a hollow portion whose diameter is reduced is divided into a central mold and side molds. In addition, the pipe end die is provided with a pressing means for pushing the end portion of the raw pipe. 6. The apparatus for manufacturing a tapered metal pipe according to claim 5, wherein the central mold is divided in a direction along the axis thereof.