JPS6115772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to preventing flattening of a steel pipe during continuous hot bending.

As shown in Fig. 1, in the hot bending method for pipes, the pipe P to be bent is placed between two sets of guide rollers.
While being supported and guided by G ₁ and G ₂ , the rotating arm A is forced to move forward, and the tip of the portion of the pipe P to be bent is adjusted to a predetermined bending radius R. Heating that heats the outer surface, inner surface, or both inner and outer surfaces of the tube P, which is tightened by the clamp C, on the radial circumference of the tube P whose surface including the axial direction of the rotation axis O of the rotary arm A is substantially orthogonal to the tube P. A device comprising a source, for example, an annular inductor I, is used to drive the inductor I to locally heat the tube P.
A method is known in which the pipe P is bent according to the bending radius R by the arm A by moving the arm A forward. According to this apparatus and method, the tube can be bent efficiently, but a flattening phenomenon occurs on the inside and outside of the bent portion of the tube in the bending direction. As shown in Figure 2, this flattening phenomenon generally occurs in the form in which the inner and outer surfaces of the pipe wall in the bending direction of the bent portion are crushed inward and become sources of stress, while at the same time the upper and lower surfaces in the bending direction are bulged out. This will occur regardless of the method of bending, unless special measures are taken to prevent flattening. In addition, in the bending method shown in Fig. 1, this flattening phenomenon affects the roundness of the pipe P directly under the inductor I just before being bent, and the flatness of the pipe P directly under the inductor I is affected. The cross section is slightly flattened as shown in FIG.
(In addition, Figures 2 and 3 schematically represent the flatness of the tube P, and the chain line represents the cross section of the tube when it is perfectly round.) In this way, just below the inductor I, The fact that the cross section of the tube P is not a perfect circle equalizes the unevenness of the gap between the tube wall and the entire circumference of the inductor I, which prevents the inductor I from uniformly heating the entire circumference of the tube P.

That is, if the gap between the inductor I and the tube P is uneven around the entire circumference, the heat generation density of the tube wall will be different, and the heating temperature will be uneven in the circumferential direction of the tube.

Therefore, the bending process using the apparatus shown in Fig. 1 is as follows.
The bending moment acting on the pipe P between the clamp C of the rotating arm A and the guide roller _G1 acts on the annularly heated portion of the pipe P that is annularly heated by the inductor I and placed in the plastic region, and this action This is done by continuously moving the pipe P in the longitudinal direction, so
As mentioned above, if the gap between the inductor I and the cross section of the pipe P directly below or almost directly below it is uneven and the heat generation density of the pipe P, that is, the heating temperature differs, the heated portion will not be able to unify the effect of the bending moment. Specifically, as shown in FIG. The tube wall is heated less and is less likely to deform than the upper and lower sides, so
This promotes flattening during bending.

Conventionally, in order to prevent flattening during the bending process of the tube as described above, a flattening prevention plate formed in a perfect circle shape was attached to the tube P after passing through the inductor I. To ensure and maintain the roundness of the pipe P directly below, on the pipe P after passing through the inductor I, a flange-like flattening clamp is attached between the clamp C and the inductor I to prevent the pipe from bending. In the front of the advancing side of the tube P of the inductor I, the side where the tube wall bulges out (the top and bottom of the tube P in Fig. 3). Measures such as bringing a bulge suppressing roller into contact with the tube in advance have been taken, but these measures are only effective when the outer diameter D with respect to the wall thickness T of the pipe P is D/T>70,
Alternatively, the bending radius R with respect to the outer diameter D of the tube is R/D<
In bending under conditions such as 3, a sufficient flattening prevention effect cannot be obtained.

In other words, if the wall thickness of the tube is small compared to the outer diameter, the rigidity of the tube is insufficient and the effect of the flattening prevention plate and clamp is not extended in the longitudinal direction of the tube, resulting in a so-called bellows phenomenon on the inner surface of the tube. In addition, the bulge suppression roller not only has a small area of action in the longitudinal direction of the pipe, but also does not act on the entire circumference of the pipe, so it is not possible to ensure or maintain roundness immediately below or in the vicinity of the inductor. It is from.

In addition, the lack of rigidity of the pipe is caused by the part where the load is concentrated when a bending moment is applied, that is, the first part.
In the device shown in the figure, a large deformation is uniformly applied to the part in contact with the guide roller _G1 , and this deformation causes the inductor I to
From flattening the outer shape of the pipe directly below,
At present, the pipe with D/T>70 is not bent by the method shown in FIG.

The present invention effectively prevents the flattening phenomenon that occurs when bending a tube as described above, particularly when bending a large-diameter thin-walled tube or a thin-walled tube with a small bending radius relative to its outer diameter. It was created for the purpose of providing a method and an apparatus for carrying out the method, and the structure of the method is as follows:
The wall surface of the tube to be bent is heated annularly by heating means such as induction heating along the longitudinal direction of the tube, while the portion to be bent is supported at both ends in the longitudinal direction, and the portion to be bent is heated. When bending is performed by applying a bending moment, in order to maintain the annularly heated portion or the cross section of the tube in the vicinity of the portion in a perfect circle or nearly a perfect circle, the effective holding internal shape conforms to the circular external shape of the tube. and a plurality of rotating bodies or sliding bodies rotating in the moving direction of the tube are arranged at approximately equal intervals so that their inscribed surfaces touch the effective inner diameter, and a tube outer shape holder is placed near the heating means. The external shape retainer is fixedly installed in front of the tube, and immediately before the portion of the tube to be bent passes through the heating means, the rotating body or sliding body suppresses the surface of the tube at the portion that is about to deform and bulge. The structure of the apparatus for carrying out this method is to support both the front and rear ends of the part of the pipe to be bent, and to apply a predetermined bend to the part to be bent. a tube supporting means for applying a bending moment while maintaining the radius; a heating means having a cooling function for locally heating the part to be bent in an annular shape and immediately cooling the heated part; In a pipe bending device, the pipe bending device comprises a moving means for relatively moving the heating means from the starting end to the rear end in the longitudinal direction of the part to be bent. A tube external shape holder is fixed in front of the heating means, and is formed by radially arranging a plurality of rotating bodies or sliding bodies that circumscribe the effective inner diameter of the tube at approximately equal intervals in the radial direction of the tube. It is characterized by this.

Next, embodiments of the present invention will be described with reference to the drawings.

In this embodiment, a bending device having the same structure as that shown in FIG. 1 is used, so the bending device will be explained using the device shown in FIG.

The pipe P to be bent is supported and guided by two sets of guide rollers G ₁ and G ₂ on the rear end side of the part to be bent, and the front end side of the part to be bent is held by a clamp C. . In other words, the guide rollers G ₁ and G ₂ and the clamp C are means for supporting the portion of the pipe P to be bent. The clamp C is fixed to the tip side of a rotating arm A that is rotatably arranged around an axis O on the inside of the bent pipe P. A thrust force F is appropriately applied from the side by a propulsion device.
Therefore, while the tube P is guided by the guide rollers G ₁ and G ₂ and moved forward in a straight line, the tip side of the tube held by the clamp C pushes the arm A and moves the arm A around the axis O. Since it will be rotated, the pipe P is connected to the guide rollers G ₁ and G ₂ and the clamp C.
It is subjected to a bending moment while being supported by the That is, in this device, two sets of guide rollers are used.
The arm A having G ₁ , G ₂ and the clamp C and the thrust force F function as means for applying a bending moment.

The pipe P to which a bending moment is applied by the above-mentioned configuration is locally heated at that time, and in this embodiment, the heating means is a plane containing the rotation axis O of the arm A. An annular high-frequency inductor I is used, which is disposed so as to surround the outer periphery of the tube P in a plane whose (perpendicular to the plane of the drawing) is orthogonal or substantially orthogonal to the straight pipe portion of the tube P. Incidentally, the inductor I includes a cooling jacket (not shown) for cooling the heated portion of the tube P. Here, the means for moving the inductor I relative to the tube P along the longitudinal direction of the tube P is in charge of the thrust force F, since the tube P is advanced by the thrust force F as described above. Therefore, the inductor I does not need to be moved and is fixedly placed.

The above constitutes a bending apparatus used for carrying out the method of the present invention.

Thus, in the method of the present invention, during the bending process using the above-mentioned apparatus, the portion of the pipe P to be bent is located immediately before passing through the inductor I, specifically, between the guide roller _G1 and the inductor I. Since the part of the pipe P to be bent is forcibly held in the cross-sectional shape of the pipe P when it is perfectly round, the roller _G1 and the inductor I
A pipe external shape holder K having a structure as described below is disposed between the pipe and the pipe.

FIG. 4 shows the structure of an example of the outer shape holder K from the front, and 1 is a mounting body provided with a circular hole 2 that conforms to the outer shape of the pipe P and has an inner diameter larger than its outer diameter. The upper and lower members 1a and 1b are divided into two in the horizontal direction, and the upper and lower members 1a and 1b are formed so that they can be separated and integrated by tightening bolts 11 or the like on both outer sides thereof. Reference numeral 3 denotes press rollers provided radially inward in the radial direction of the circular hole 2, and the distance between the opposing press rollers 3, 3 is adjusted so as to match or approximately match the outer diameter of the pipe P when it is perfectly round. There is.

That is, as shown in FIG. 5, each of the rollers 3 has two rollers 3 rotatably mounted on a shaft 32 at the bottom of a mounting bracket 31 that is approximately L-shaped relative to the side cross section of the mounting plate 1. At the same time as mounting, the upper part of the metal fitting 31 is fixed to the attachment body 1 with a bolt 33, so that the rollers 3, 3 are disposed around the circular hole 2 toward the center thereof.

Since the external shape holder K is used to maintain the external shape of the pipe P located between the guide roller _G1 and the inductor I in the bending device in a perfect circle, basically The external shape holder K having the above structure is arranged between the guide roller _G1 and the inductor I, and the part of the pipe P to be bent passes through the holder part before reaching the action area of the inductor I. However, for the purpose of improving the effect of the method of the present invention,
The structure of the external shape holder K and its arrangement position can be configured as described below.

First, regarding the structure, in the above embodiment, the attachment body 1 was formed into an upper and lower split type, but in this case, the upper and
The gap g between the joints of the lower members 1a and 1b may be adjustable. This is because the shape holder K maintains the roundness of the pipe P directly under or near the inductor I, and also prevents flattening of the pipe P directly below or near the inductor I during bending. , in view of the fact that this is caused by the bulge of the pipe wall in the vertical direction at that part, in order to actively prevent this flattening, the circular shape formed by each roller 3 of the attachment body 1 (inscribed in each roller 3) is This is to make the circle (circle) into a slightly inverted flat shape. Note that the external shape of the attachment plate 1 is not limited to the shape shown in the drawings. In short, circular hole 2
Any shape may be used as long as it can form the shape.

In order to make the circular shape formed by each of the rollers 3 into an inversely flat shape, the attachment fittings 3 supporting the rollers 3 are used.
1 may be movable and adjustable in the radial direction of the circular hole 2 relative to the attachment body 1. For example, the 6th
As shown in the figure, the bolt holes 33a of the mounting bracket 31 are formed into elongated holes, or as shown in Figure 7, a plurality of bolt holes are arranged in a row in the vertical direction.

In this way, the shape and size of the circle formed by each roller 3 can be adjusted arbitrarily, so not only can the degree of reverse flatness be adjusted freely, but it can also be adapted to the size of the outside diameter of the pipe. It is convenient to be able to do so.

In addition to the above example, means for adjusting the inner diameter of the circle formed by each roller 3 include those shown in FIGS. 8 and 9.
As shown in the figure, instead of directly attaching the mounting bracket 31 of the roller 3 and the mounting body 1, the bracket 31 is separated into upper and lower members 31a and 31b, and both are placed in the radial direction of the circular hole 2. There is also a method of attaching it via a screw 34 or a hydraulic cylinder 35. In this way, the position of each roller 3 in the radial direction of the circular hole 2 can be easily and reliably adjusted and secured.

Note that when two or more rollers 3 are provided, the mounting bracket 31 of the presser roller 3 is attached to the upper half 31 as shown in FIG.
a and a lower half 31b, both of which are 31a and 31b.
1b is a connecting shaft 3 parallel to the mounting shaft 32 of each roller 3.
6 may be connected. According to this, since the push roller 3 follows the irregularities, etc. in the longitudinal direction of the pipe P, the guide of the pipe P becomes smooth.

Next, the outer shape holder K configured as described above
is the relationship between the outer diameter D and wall thickness T of the pipe P to be bent, the relationship between the length l of the part to be bent and the outer diameter D, or the reverse flatness forced by the shape holder K. Therefore, adjust the installation position accordingly.

This is the outer diameter D and wall thickness T of the pipe P to be bent.
The degree of rigidity determined by In particular, the outer shape holder K of the present invention
This is to ensure roundness commensurate with the respective pipes P directly below or substantially directly below the inductor I. As for this specific position, as a result of various experiments conducted by the inventor, it has been found that as the length l of the bent portion becomes smaller with respect to the outer diameter D of the tube, it is preferable to move the outer shape holder K closer to the inductor I side. that the results are obtained, and for tubes of the same size and shape,
We have learned that it is necessary to change the distance between the holder K and the inductor I depending on the degree of inverse flatness that is formed on the tube P by the outer shape holder K. If you take this into account, you can get good results.

External shape holder K for pipe P configured as described above
In this embodiment, the guide rollers G ₁ and G ₂ in the bending device are attached to the front end side of the receiving plate B (see Fig. 1) and are positioned in front of the inductor I, so that the pipe P During the bending process, the outer shape of the pipe P can be forcibly maintained in a perfect circular shape before the pipe P is heated by the inductor I, and therefore, a bending moment is created between the rotating arm A and the guide roller _G1 . This can prevent the pipe P from flattening even if this occurs.

In addition, since the roundness of the pipe P is forcibly ensured by the shape holder K immediately before it is heated by the inductor I, the gap between the inductor I and the heated part is the entire circumferential area of the pipe P. Therefore, uniform heating is possible, and it is possible to prevent flattening of the tube due to non-uniform heating.

The effect of the method or device of the present invention can be further enhanced by applying a conventionally known flattening prevention means to the bent portion of the pipe P after it has been heated.

Since the present invention is as described above, it is possible to produce materials that are virtually impossible to bend, such as thin-walled large-diameter pipes and the like, where flattening or bellowing phenomena occur to a large extent during bending. Since bending can be performed without bending, it is extremely useful when applied to bending thin-walled, large-diameter pipes, etc. It goes without saying that the method and apparatus of the present invention can be applied effectively to the flattening phenomenon even when applied to ordinary pipe bending processes.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an example of a bending device equipped with the device of the present invention, Fig. 2 is an explanatory plan view showing the flattening of a tube in conventional bending process, and Fig. 3 is a plan view of an example of a bending device equipped with the device of the present invention. FIG. 4 is an explanatory side view showing the flatness of the tube, FIG. 4 is a front view of an example of the device of the present invention, and FIG.
The figure is an enlarged cross-sectional view taken along the line V-V' in Figure 4, Figures 6 to 9 are vertical side views showing examples of the mounting structure for the presser roller, and Figure 10 is an enlarged view of the mounting bracket for the presser roller. It is a side view of another example. P...Pipe, _G1 , _G2 ...Guide roller, A...
Rotating arm, C... Clamp, O... Rotating axis, I
...Inductor, F...Thrust, K...Outline holder, 1
...Attachment plate, 1a...Upper member of attachment plate, 1b...
Lower member of attachment plate, 2... circular hole, 3... presser roller, 31... attachment fitting, 32... shaft, 33... bolt.

Claims (1)

[Scope of Claims] 1. The wall surface of the tube to be bent is heated annularly by heating means such as induction heating and moved along the longitudinal direction of the tube, and a bending moment is applied to the heated portion to bend the tube. In this method, in order to maintain the section of the tube at or near the annularly heated section in a perfect circle or a nearly perfect circle, the effective internal shape of the tube conforms to the circular outer shape of the tube, and A tube external shape holder in which a plurality of rotating bodies or sliding bodies rotating in the moving direction are arranged at approximately equal intervals so that their inscribed surfaces touch the above-mentioned effective inner diameter is fixed in front near the heating means, and the above-mentioned Immediately before the portion of the tube to be bent passes through the heating means, the portion of the tube that is to be bent is passed through the shape retainer while being suppressed by the rotating body or sliding body at the portion of the tube that is about to deform and bulge. A method to prevent flattening during hot bending of pipes. 2. Pipe support means that supports the front and rear parts of the part of the pipe to be bent and applies a bending moment to the part to be bent while maintaining a predetermined bending radius; a heating means equipped with a cooling function that heats the heating part in an annular manner and immediately cools the heated part; and a heating means that has a cooling function that heats the heating part in an annular manner and cools the heating part immediately after that, and the heating means is arranged relative to each other in the longitudinal direction of the part to which the bending moment is applied, from the starting end to the rear end. In the pipe bending apparatus, a plurality of rotating bodies or sliding bodies circumscribing an effective inner diameter corresponding to the circular outer shape of the pipe to be bent are moved radially in the radial direction of the pipe. 1. An apparatus for preventing flatness in hot bending of a tube, characterized in that tube external shape holders formed at approximately equal intervals are fixedly provided in front of the heating means.