JP2009255165A - Method and device for bending pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for working by which bending is applied so as to have a desired bending shape at high work efficiency without generating wrinkles on the inside of a bending part by using a high-strength thin-walled steel pipe as a pipe stock. <P>SOLUTION: After the pipe stock 10 is charged into the caliber 1a of a fixed bending die 1 and held with the die and a clamping die 3, and then the pipe stock is worked into a prescribed shape by turnably moving turnably movable pressing dies 2 along the bending shapes of the bending dies while contracting the diameter so as to be a prescribed circumference contraction rate by pressing turnably movable pressing dies 2 against a prescribed place of the pipe stock. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a bending method of a high-strength thin-walled steel pipe, which is a pipe suitable as a member for automobile undercarriage, bumper, body and the like, and in particular, bending of a pipe subjected to hydroforming preforming bending. It relates to a method and an apparatus.

For example, as shown in Non-Patent Document 1, a pipe is bent and supported by a pipe support member that is in contact with two support points in the length direction, and between the two support points. This is a processing method of bending a pipe by pushing the pipe portion with a press bending die.
As an efficient pipe bending method, a rotary drawing bending method is known. In the rotary pulling bending method, the bending die is clamped between the rotatable bending die and the push die that can go straight in the tube axis direction before bending, and the tip of the tube is clamped to the bending die. By rotating the tube, the tube can be bent along the outer periphery of the bending die. Such a rotary drawing bending method is widely applied to bending a circular cross-section tube.

  For example, Patent Document 1 discloses an apparatus for bending a long material in which a space is provided in an axial center portion by using this rotary pull bending method. The bending apparatus described in Patent Document 1 includes a molding drum having a curved outer peripheral surface, a tension holding member that holds the tip of the material and pulls it along the outer peripheral surface of the molding drum, and a tensile direction with respect to the material. And resistance force applying means for applying a resistance force in the opposite direction. The resistance applying means includes a pressure shoe and a pressure device that presses the pressure shoe against the material. The pressure shoe applies pressure to the surface of the material to cause a dynamic frictional resistance to act. By this resistance force applying means, a tensile resistance force is applied to the material, the bending stress generated when the material is bent can be relieved, flat deformation and wrinkle deformation can be suppressed, and further, the buckling deformation force can be relieved. .

JP 11-267765 A

The Japan Society for Technology of Plasticity “Tube Forming” Corona, October 30, 1992, P38-39

  When the material pipe is processed into a member having the shape shown in FIG. 3, such as a bumper of an automobile, that is, a member having a linear shape at the center and a bent shape at both ends, the above-described press bending method is used. Then, there is a problem that the pipe does not follow the bending mold and cannot be processed into a desired shape. In addition, when the material pipe is a large-diameter high-strength thin-walled steel pipe, there is a problem that wrinkles are generated inside the bend. In addition, when using the rotary draw bending method, a mandrel is used and multiple processes are required, and the central part moves with the rotary draw bending process, so both ends cannot be bent simultaneously. There was a problem that work efficiency was lowered.

  The present invention advantageously solves such problems of the prior art, and uses a high-strength steel pipe, preferably a high-strength thin-walled steel pipe as a raw material pipe, with high work efficiency without generating wrinkles inside the bent portion. It is an object of the present invention to provide a pipe bending method and apparatus that can be bent so as to have a desired bending shape. As used herein, “high-strength steel pipe” refers to a steel pipe having a tensile strength TS of 680 MPa or more, and “thin-wall steel pipe” refers to a steel pipe having a thickness / outer diameter ratio (t / D) of 4% or less. Say.

  In order to achieve the above object, the present inventors have intensively studied, and as a result, it is conceivable that the circumference of the bending portion of the material pipe should be narrowed and bent so as to have a predetermined bending shape. did. For this purpose, the inventors came up with the idea of using a fixed bending mold and a pressing mold that can be rotated (meaning rotation or rotation + movement of the rotation center). Thereby, even if it was a high-strength thin-walled steel pipe, it discovered that generation | occurrence | production of a wrinkle could be prevented inside a bending part. In addition, using fixed bending dies and two rotary movable pressing dies, it was possible to perform bending at both ends of the pipe at the same time, and the knowledge that machining efficiency was improved was also obtained. .

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(Claim 1)
A high-strength steel pipe is used as a material pipe, and when bending a predetermined portion of the material pipe, the material pipe is inserted into a caliber of a fixed bending mold, and the bending mold and the clamping mold are used. Rotate along the bending shape of the bending mold while pressing the pressing mold, which can be rotated, to a predetermined location of the material pipe and reducing the diameter so as to obtain a predetermined circumferential draw ratio. A pipe bending method characterized by moving and processing into a predetermined bending shape.
(Claim 2)
2. The pipe bending method according to claim 1, wherein the predetermined circumferential drawing ratio is a maximum drawing ratio of 3% or more of the bending portion.
(Claim 3)
3. The pipe bending method according to claim 1, wherein the bending die is a bending die having a linear shape at a central portion in a longitudinal direction and the predetermined bending shape at both end portions.
(Claim 4)
The pipe bending method according to any one of claims 1 to 3, wherein the high-strength steel pipe is a 780 MPa or higher class high-strength thin-walled steel pipe.
(Claim 5)
The pipe bending method according to any one of claims 1 to 4, wherein the high-strength steel pipe is a 1300 MPa class high-strength thin-walled steel pipe.
(Claim 6)
Furthermore, a wrinkle holding tool is installed between the bending die and the material pipe, and when the processing is performed into the predetermined bending shape, the tool is rotated and moved along the bending shape of the bending die. Item 6. The pipe bending method according to any one of Items 1 to 5.
(Claim 7)
A pipe bending apparatus for bending a predetermined portion of a material pipe made of a high-strength steel pipe, and having a predetermined bending shape capable of contacting the material pipe at one end or both ends of a line segment A bending die, a clamping die for restraining the material pipe at the position of the line segment, and a predetermined circumferential length by pressing the material pipe against a predetermined portion of the material pipe and bringing the predetermined portion into contact with the bending die. A pipe bending apparatus characterized by having a pressing mold that can be reduced in diameter by a drawing ratio and that can rotate and move along the bending shape of the bending mold.
(Claim 8)
The pipe bending apparatus according to claim 7, wherein the predetermined circumferential drawing ratio is a circumferential drawing ratio of 3% or more at the maximum of the bending portion.
(Claim 9)
The pipe bending apparatus according to claim 7 or 8, wherein the bending mold is a bending mold having a linear shape at a central portion in a longitudinal direction and the predetermined bending shape at both ends.
(Claim 10)
The pipe bending apparatus according to any one of claims 7 to 9, wherein the high-strength steel pipe is a 780 MPa or higher grade high-strength thin-walled steel pipe.
(Claim 11)
The pipe bending apparatus according to any one of claims 7 to 10, wherein the high-strength steel pipe is a 1300 MPa class high-strength thin-walled steel pipe.
(Claim 12)
Furthermore, it has a wrinkle pressing tool installed between the said bending metal mold | die and the said raw material pipe, The pipe bending apparatus of any one of Claims 7-11 characterized by the above-mentioned.

  According to the present invention, a high-strength steel pipe can be bent into a desired bending shape with high work efficiency without causing wrinkles on the inner side of the bent portion and without causing a large thickness reduction. Has an exceptional effect. In addition, according to the present invention, it is possible to simultaneously form different bent-shaped processed portions at both ends of the pipe, and there is an effect that the productivity is remarkably improved and the efficiency of the bending processing is improved. .

  Moreover, according to this invention, the wrinkle of the bending side surface which may generate | occur | produce when a bending angle is large can be suppressed.

(a) is the schematic which shows the initial stage in one example of this invention, (b) is sectional drawing which shows the caliber of a pressing mold, (c) is sectional drawing which shows the caliber of a bending mold. It is the schematic which shows the completion | finish stage of the bending process from the initial stage of FIG. It is the schematic which shows the pipe shape in the completion | finish stage of FIG. It is the schematic ((a) side view, (b) top view) which shows an example of the suitable form of this invention apparatus. It is the schematic ((a) before bending process, (b) after bending process) which shows one example of this invention embodiment which added the wrinkle pressing tool.

  In the pipe bending method of the present invention, as shown in FIG. 1, for example, as shown in the initial stage, a bending die 1, a pressing die 2, and a clamping die 3 are used and arranged as shown. The bending apparatus of the present invention taking such an arrangement form as an example is a bending die 1 having a predetermined bending shape capable of contacting the material pipe 10 at one end or both ends of a line segment, A clamping die 3 that restrains the material pipe 10 at the position of the line segment, and a predetermined portion of the material pipe 10 that is pressed against the bending die 1 to press the material pipe 10 at a predetermined peripheral length. It has a pressing mold 2 that can be reduced in diameter and that can rotate and move along the bending shape of the bending mold 1.

  FIG. 1 shows an example in which a bending die 1 having a linear shape at the center in the longitudinal direction and a bending shape at both ends is used, but the bending die 1 to be used is not limited to this. It goes without saying that a bending mold having a bent shape only on one side may be used. However, in order to efficiently bend the material pipe into an appropriate bending shape in which the line segment is bent at two places, as shown in the example of FIG. 1, it has a linear shape at the center in the longitudinal direction and a bent shape at both ends. It is preferable to use a bending die 1.

In this example, the bending mold 1 is an integral type, but the present invention is not limited to this, and a multi-separation type bending mold may be used. In this multi-separation type, the length of the remaining portion (linear shape portion) excluding the bent shape portion may be shorter than the length of the clamping die 3, and the linear shape portion may be arranged away from the bent shape portion.
The bending mold 1 is fixed. The fixing method is not particularly limited. The bending die 1 is engraved with a caliber 1a so that the material pipe 10 can come into contact therewith. Kariba 1a bending mold 1, the area where the pipe abutment surface in the width direction, has the same curved shape as the caliber of the inner surface having a diameter D ₁ that conforms to the diameter d ₀ of the material pipe 10, and bending In the (bending portion), the pipe contact surface in the longitudinal direction is engraved so as to have a curved shape with, for example, the curvature radii R ₁ and R ₂ , and in other regions, the pipe contact surface in the longitudinal direction is It is engraved so as to exhibit a linear shape. In addition, it is preferable that the caliber depth d1 of the bending die ₁ is not more than half of the outer diameter of the pipe.

  The pressing mold 2 is disposed so as to be able to rotate along the bending shape of the bending mold 1 by pressing the material pipe 10. For example, as shown in FIG. 4, the pressing mold 2 includes a hydraulic cylinder (not shown) and a radially moving rail mechanism 20 that can move in a bending radial direction 31 so that pressing is possible, and a tangential direction 32 of rotation. A tangential moving rail mechanism 21 on which the radial moving rail mechanism 20 is mounted so as to be movable, and a rotary table mechanism 22 on which the tangential moving rail mechanism 21 is mounted so as to be rotatable. preferable. Reference numeral 30 denotes a rotation center of the rotary table mechanism 22. However, depending on the method of use, the tangential moving rail mechanism 21 may not be provided, and the radial moving rail mechanism 20 may be mounted directly on the rotary table mechanism 22.

The pressing die 2 is provided with a caliber 2a so that the material pipe 10 can come into contact therewith. Kariba 2a of the pressing mold 2 has the same curved shape as the caliber of the inner surface having a diameter D ₂ of the pipe abutment surface in the width direction is adapted to the diameter d ₀ of the material pipe 10, and the peripheral material pipe 10 It is adjusted caliber depth d ₂ so as to be able to narrow a length in a predetermined circumferential length drawing rate is engraved. Here, the circumference drawing ratio is an amount defined by the following equation.

Peripheral drawing ratio = (Pipe outer circumference before bending-Pipe outer circumference after bending) / Initial pipe outer circumference (× 100%)
Since the circumference drawing ratio is not the same over the entire bent portion, the predetermined circumference drawing ratio here means the maximum value in the bent portion.
Further, the clamping die 3 holds the material pipe 10 between the bending die 1 and does not cause the sliding movement of the straight portion of the material pipe 10 during bending, and can sufficiently suppress the bending reaction force. The material pipe 10 is arranged to be fixable to the extent. The clamping mold 3 is engraved with a caliber (not shown) so that the material pipe 10 can come into contact therewith. This caliber is engraved so that the pipe contact surface has the same bent shape as the inner surface of the hole type having a hole diameter adapted to the outer diameter of the material pipe 10 in the width direction so that it has a linear shape in the longitudinal direction. The

In the present invention, first, the material pipe 10 is held by the bending mold 1 and the clamping mold 3. Next, the pressing die 2 is brought into contact with a portion where the material pipe 10 is to be bent, that is, a portion to be bent. This state is schematically shown in FIG. In FIG. 1, the radii of curvature R ₁ and R ₂ at both ends of the bending die 1 may be the same or different from each other.
Then, while pressing the pressing mold 2 against the material pipe 10, the rotating mold 2 is rotated and moved along the bending shape of the bending mold 1 (that is, the pressing mold 2 is rotated around the rotating shaft or the rotating shaft is further moved). ) As a result, the circumference of the bent portion of the material pipe 10 can be reduced, and the material pipe 10 can be processed into a predetermined bent shape. Because, in the present invention, the pressing mold 2, so as to be able to squeeze the circumference of the material pipe at a predetermined circumferential length drawing rate, and adjust the caliber depth d ₂ so as to be smaller than the pipe radius This is because the cariba 2a is engraved. By rotating the pressing die 2 along the bending shape of the bending die 1 while reducing the circumference of the material pipe 10 (ie, reducing the diameter of the bent portion of the material pipe 10), Even if the material pipe 10 is a high-strength thin-walled steel pipe, it is possible to suppress the occurrence of wrinkles on the inner side of the bending (that is, the inner bending side of the bent portion after processing).

FIG. 2 shows an end stage of the press bending process with FIG. 1 as an initial stage. The bent portion is narrowed and contracted by a predetermined peripheral drawing ratio by pressing and rotating movement of the pressing die 2 and bends following the bending shape of the bending die 1. The pipe 10 has a shape as shown in FIG.
However, if the predetermined perimeter drawing ratio is less than 3% at the maximum of the bent portion (of course, limited to more than 0%), the effect of preventing wrinkling on the inner side of the bend may not be possible depending on the relationship between the t / D of the tube and the bend R In order to be stable, it is preferable to set the predetermined circumferential length drawing ratio to 3% or more.

In addition, when the material pipe is a high strength thin steel pipe of 780 MPa or more, the wrinkle generation suppressing effect on the inner side of the bending according to the present invention is more prominently exhibited compared to the case of a high strength thin steel pipe lower than this. In the present invention, it is preferable to use a high strength thin steel pipe of 780 MPa or higher class for the material pipe from the viewpoint of remarkable effect. More preferably, it is a 1300 MPa class high strength thin-walled steel pipe.
By the way, when the material pipe is bent using a bending die and a pressing die while reducing the diameter (circumferential drawing), for example, the t / D of the material pipe becomes smaller than 2.5% and the bending R is about 250 mm. In such a case, if the bending angle is increased to, for example, more than 20 degrees, wrinkles of the bent side surface of the pipe may occur during the bending process. Further, when the t / D of the material pipe is reduced to be less than 1.8%, for example, when the bending R is 250 mm, the bending side of the pipe is likely to be wrinkled even if the bending angle is further smaller than 20 degrees.

  For this, for example, as shown in FIG. 5, a wrinkle pressing tool 5 is installed between the bending die 1 and the material pipe 10, and the bending shape of the bending die 1 is processed during processing into a predetermined bending shape. It is possible to suppress the generation of wrinkles on the bent side surface by rotating along the axis. Such a wrinkle pressing tool 5 can be fixedly attached to a base on which the pressing mold 2 is installed. Further, the wrinkle holding tool is installed so that the inner surface of the caliber contacts the outer surface of the pipe, or is installed slightly apart as will be described later.

However, according to the means to which the wrinkle pressing tool 5 is added, the pressing amount of the pressing mold 2 is suppressed, so that wrinkles inside the bending tend to be easily generated. In order to alleviate this tendency, the initial position of the wrinkle pressing tool 5 is set with respect to the reference surface perpendicular to the tube axis of the material pipe in the initial set state passing through the bending curvature center position C as shown in FIG. and the opposite side, the distance x ₀ from the reference surface to blank holding tool 5 (proximal end) of, with respect to the material pipe outer diameter D, may be set to _{0 ≦ x 0 ≦ D / 2} ,.

In addition, when it is desired to increase the pressing amount of the pressing mold 2 under the use of the wrinkle pressing tool 5, the thickness y of the pipe bending inner abutting portion of the wrinkle pressing tool 5 is set after making x0 larger than ₀ mm. _0, may be increased to the extent that they do not overlap the bending tool 1, but the magnitude of y ₀ is preferably set to 5% or less of the material pipe outer diameter D.

Using a 1300 MPa class high-strength thin steel pipe with an outer diameter of 89.1 mm and a wall thickness of 2.0 mm as the material pipe, bending radius R = 300 mm, bending angle = A bending process of bending at 20 degrees was carried out to determine visually whether or not molding was possible (OK / NG), and the processing time required for bending 1000 tubes was measured. The results are also shown in Table 1.
From Table 1, in Example 1 of the present invention, the generation of wrinkles on the inner side of the bend was suppressed by pressing bending while reducing the diameter, and the processing time was about 3 hours by simultaneous bending at two locations. On the other hand, in Comparative Example 1, the processing time was the same as in Example 1 of the present invention by bending at two locations simultaneously, but wrinkling occurred inside the bend due to normal pressing bending without a reduced diameter, and molding was impossible. Met. Further, in Comparative Example 2, molding was possible by rotational drawing as in the case of Example 1 of the present invention, but only one place could be processed at a time by rotational drawing, and a total of two processing was performed for two places. Therefore, the processing time was about 6 hours.

Using a 1300MPa class high-strength thin steel pipe with an outer diameter of 89.1mm and a wall thickness of 2.0mm as a material pipe, the bending radius R = 250mm, bending angle = A bending process of bending at 25 degrees was performed, and the presence / absence of wrinkles on the bent side surface and the bent inner side was visually determined. The results are also shown in Table 2.
From Table 2, it can be seen that, when the bending angle is large, by adding a wrinkle pressing tool as in Example 2 of the present invention, it is possible to suppress not only wrinkling on the inner side of the bending but also generation of wrinkles on the bent side surface.

1 Bending die 1a Bending die caliber 2 Pressing die 2a Pushing die caliber 3 Tightening die 5 Wrinkle holding tool
10 pipe (material pipe or processed pipe)
20 Radial moving rail mechanism
21 Tangential moving rail mechanism
22 Rotary table mechanism
30 center of rotation
31 Bending radius direction
32 tangential direction of rotation

Claims (12)

  A high-strength steel pipe is used as a material pipe, and when bending a predetermined portion of the material pipe, the material pipe is inserted into a caliber of a fixed bending mold, and the bending mold and the clamping mold are used. Rotate along the bending shape of the bending mold while pressing the pressing mold, which can be rotated, to a predetermined location of the material pipe and reducing the diameter so as to obtain a predetermined circumferential draw ratio. A pipe bending method characterized by moving and processing into a predetermined bending shape.   2. The pipe bending method according to claim 1, wherein the predetermined peripheral drawing ratio is a maximum drawing ratio of 3% or more at the maximum of the bent portion.   3. The pipe bending method according to claim 1, wherein the bending die is a bending die having a linear shape at a central portion in a longitudinal direction and the predetermined bending shape at both end portions.   The pipe bending method according to any one of claims 1 to 3, wherein the high-strength steel pipe is a 780 MPa or higher class high-strength thin-walled steel pipe.   The pipe bending method according to any one of claims 1 to 4, wherein the high-strength steel pipe is a 1300 MPa class high-strength thin-walled steel pipe.   Furthermore, a wrinkle holding tool is installed between the bending die and the material pipe, and when the processing is performed into the predetermined bending shape, the tool is rotated and moved along the bending shape of the bending die. Item 6. The pipe bending method according to any one of Items 1 to 5.   A pipe bending apparatus for bending a predetermined portion of a material pipe made of a high-strength steel pipe, and having a predetermined bending shape capable of contacting the material pipe at one end or both ends of a line segment A bending die, a clamping die for restraining the material pipe at the position of the line segment, and a predetermined circumferential length by pressing the material pipe against a predetermined portion of the material pipe and bringing the predetermined portion into contact with the bending die. A pipe bending apparatus characterized by having a pressing mold that can be reduced in diameter by a drawing ratio and that can rotate and move along the bending shape of the bending mold.   The pipe bending apparatus according to claim 7, wherein the predetermined circumferential drawing ratio is a circumferential drawing ratio of 3% or more at the maximum of the bending portion.   The pipe bending apparatus according to claim 7 or 8, wherein the bending mold is a bending mold having a linear shape at a central portion in a longitudinal direction and the predetermined bending shape at both ends.   The pipe bending apparatus according to any one of claims 7 to 9, wherein the high-strength steel pipe is a 780 MPa or higher grade high-strength thin-walled steel pipe.   The pipe bending apparatus according to any one of claims 7 to 10, wherein the high-strength steel pipe is a 1300 MPa class high-strength thin-walled steel pipe.   Furthermore, it has a wrinkle pressing tool installed between the said bending metal mold | die and the said raw material pipe, The pipe bending apparatus of any one of Claims 7-11 characterized by the above-mentioned.

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