JPH05326A - Bending correction device for long material with circular cross section - Google Patents

Abstract

(57) [Abstract] [Purpose] A bend with a short cycle, especially a bend at the end of a metal material such as a metal rod or a metal tube having a circular cross section, can be corrected accurately with a simple roll shape and at high speed. [Structure] Stands I, III equipped with hourglass-shaped rolls 1, 2.
A disc roll having an IV and a stand II having a plurality of bending rolls 3, 4, and 5, and the bending rolls 3, 4, and 5 of the stand II are located in the same order from the entrance side.
In the roll set composed of 3b, 4b, 5b, 3c, 4c, 5c, 3d, 4d, 5d, disk rolls 3b, 4b, 5b, 3c, 4c, 5c, 3d, 4d, which constitute each roll set. At least one diameter of 5d is made different so that the pass line X-X line of the metal tube P is displaced from the mill center line Y-Y line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending correction capable of correcting bending of a solid material such as a metal rod or a metal tube or a long material having a hollow circular cross section, particularly a short period bending and an end bending at a high speed. Regarding the device.

[0002]

2. Description of the Related Art Solid, which is hot-worked or cold-worked,
Ordinarily, a long material having a hollow circular cross section has a bend, and various straightening machines have been conventionally proposed to correct the bend. FIG. 10 is a schematic view showing a typical four-stand / seven-roll bending straightening machine that has been conventionally proposed.

In FIG. 10, reference numerals 71, 72, 73 and 74 are all hourglass roll stands, and each hourglass roll stand 71, 72,
The metal pipes P, 73 are provided with two hourglass-shaped rolls, each of which has an axial center line inclined at a predetermined angle and are spaced apart from each other by a predetermined distance.
The stand positions are set so that the path lines of metal rods, etc. are displaced left, right, or upward and downward alternately. The hourglass roll stand 74 is located at the exit end and is provided with one hourglass roll. Each roll is rotatably driven by a drive source (not shown), and the metal pipe P passed between the rolls is advanced while being applied with rotation and bending force to correct the metal pipe P.

By the way, in such a conventional straightening machine, since the stand is arranged so as to be displaced upward, downward, or alternately left and right, and a bending force is applied between the stands, a roll shape is applied. On the other hand, it is not necessary to pay relatively strict attention to itself, but the bending correction function is limited by the stand interval,
There is a structural limit to the bending correction of a cycle shorter than the stand interval, and there is a problem that the bending of the end of the metal tube or the metal rod cannot be corrected.

As a countermeasure against this, a straightener as shown in FIG. 11 has been proposed (Japanese Patent Publication No. 60-33567). FIG. 11 is a schematic diagram showing a conventional 4-stand, 8-roll bending straightening machine, which is also composed of 4 hourglass-shaped roll stands. If the roll length L of the intermediate drum-shaped roll stands 82,83 is set larger than the roll length of the shaped roll stand 84, and the profiles (curvatures) of the upper and lower rolls of the intermediate drum-shaped roll stands 82,83 are different. It has been configured. As a result, the contact length between the roll and the metal rod or metal tube at the intermediate stand is set to be long, and the bending of the end of the metal rod or metal tube can be corrected.

[0006]

However, in such a structure, since the roll cylinder length becomes large, the roll diameter must be increased in order to secure the roll rigidity, and the roll stand must be strengthened, resulting in an increase in equipment cost. There was a problem that was inevitable.

As a countermeasure against this, the present inventor arranges two or three bending rolls constituted by providing a plurality of disc rolls on one roll shaft around the pass line of the metal pipe and the metal rod, and makes them relative to each other. A bend straightening device that makes it possible to straighten the bend of the metal rod or metal tube by repeatedly giving a short cycle bending between the disc rolls by changing the diameter of the facing disc roll. I have already proposed (Japanese Patent Application No. 3-7415)
No. 6).

Since this bend straightening device can impart a relatively large bend between the disc rolls, it is not always necessary to lengthen the roll cylinder length, and the contact length between the disc roll and the metal tube or metal rod is localized. Therefore, the load carried by the stand is small, and the equipment is compact and the equipment cost can be reduced. On the other hand, the inclination angle of each bending roll with respect to the pass line can be set to the same level as shown in Figs. 10 and 11. Is required to be set to 20 to 30 °, which complicates the equipment, and when setting such a large inclination angle, in order to avoid the separation of the bending roll shaft end from the mill center line, The diameter of the disc roll increases with respect to the width, and the rigidity of the disc roll itself becomes a problem. It should be noted that it is conceivable to increase the rotation speed of the roll instead of increasing the inclination angle, but there was a problem that whirling became a problem when correcting a long metal rod or metal tube.

The present inventor has found the following facts as a result of an experiment and a research for improving the straightening speed using a bending roll using a combination of disc rolls. For example, in the method of increasing the straightening speed by increasing the inclination angle β of the roll shaft with respect to the mill center line, the roll peripheral speed is given by the following formula. Axial component Vx = (πDn / 60) ・ sin β Circumferential component Vθ = (πDn / 60) ・ cos β where D: roll diameter, n: roll speed (rpm)

Now, for example, when Vx and Vθ are calculated when β is set to 10 ° and 30 °, the following formula is obtained. Vx (β = 30 °) = 2.88 × Vx (β = 10 °) Vθ (β = 30 °) = 0.88 × Vθ (β = 10 °) Therefore, there is no big difference in Vθ, but the difference in Vx is large. Become.

Increasing the inclination angle to increase the straightening speed is, of course, necessary even if the roll shape needs to be corrected by the change in the positional relationship between the roll axis and the mill center line due to the difference in the inclination angle β. This means that there is no big difference from increasing the forward speed by applying external force without increasing the. Therefore, it is conceivable to simply use a pushing device or a tensioning device as a means for applying an external force to the material, but in view of the bending correction function, combining it with a conventionally known drum-shaped roll stand improves the correction speed. It was found to be effective for.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a curved straightening material for a circular cross-section material such as a metal rod or a metal tube at a high speed and effectively for the end portion of the material. It is possible to provide a straightening device for a long material having a circular cross-section.

[0013]

A bending correction device for a long member having a circular cross section according to the present invention comprises a plurality of bending rolls in which at least three or more disk rolls are arranged at intervals in the axial direction, The eccentricity of at least one of the centers of common circumscribing circles of disc rolls facing each other between the bending rolls is eccentric with respect to the mill center line. It is characterized in that at least one of the stands and a plurality of stands provided with concave rolls are arranged in a line. In another straightness correcting apparatus for a long member having a circular cross section according to the present invention, the bending roll has at least one of the disk rolls forming the common circumscribing circle having an eccentric center with respect to a mill center line. It is characterized by being.

[0014]

In the apparatus of the present invention, by using at least one bending roll stand and a plurality of hourglass-shaped roll stands by this, the bending roll stand alone is used while ensuring the correction function for the material end portion. It is possible to significantly improve the correction speed as compared with the case.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. (Embodiment 1) FIG. 1 is a schematic side view of a straightening apparatus for bending a long member having a circular cross section according to the present invention, in which I, II, III, I are shown.
V is a stand and P is a metal tube. The stands I and II to IV are arranged with their mill center lines staggered with respect to each other (offset), and the metal pipe P is moved in the direction of the arrow and repeated at a relatively long cycle between the stands. It is designed to impart rotational bending.

Each of the stands I, III, and IV has a pair of hourglass-shaped rolls 1 and 2, and the stand II has three bending rolls 3, 4, and 5. Drum-shaped rolls 1, 2
In each case, the curvature of the peripheral surface is set to be the same, and the roll axes thereof are arranged at an inclination angle of approximately 30 ° with respect to the path line X-X line of the metal tube P, and they are oriented in the same direction by a drive source (not shown). It can be rotated.

On the other hand, the bending rolls 3, 4 and 5 are respectively provided with five disc rolls 3a to 3e on the roll shafts 3g, 4g and 5g, respectively.
It is configured by providing spacers 3s, 4s, 5s between each other and 4a to 4e, 5a to 5e, and arranged at an appropriate inclination angle or inclination angle, crossing angle with respect to the mill center line. The driving source (not shown) can be driven to rotate in the same direction at substantially the same rotation speed as the hourglass-shaped rolls 1 and 2.

FIG. 2 is a front view of the bending roll of the stand II as seen from the entrance side, FIG. 3 (a) is a side view taken along the line III--III of FIG. 2, and FIG. 3 (b) is a side view of the disc roll. As shown in FIGS. 2 and 3, each of the bending rolls 3, 4 and 5 has five disc rolls 3a, 3b to 3e, 4a, 4b to 4e, 5a, 5b to 5e on the respective roll shafts 3g, 4g and 5g. Are concentrically and integrally fixed to each other with a small-diameter cylindrical spacer 6 interposed therebetween, and the roll shafts 3g, 4g, 5g are inclined with respect to the mill center line Y-Y line, respectively. (However,
Indicates the inclined and crossed arrangement state), and the disk rolls 3a, 4a, 5a, 3b, 4b, 5b, ..., 3 located in the same order from the entrance side of each bending roll 3, 4, 5
Each of e, 4e, and 5e is arranged in a state of being located on substantially the same plane orthogonal to the mill center line Y-Y line, and is driven to rotate in the same direction by a drive source (not shown) and by a reduction device (not shown). It is possible to move to and from the mill center line Y-Y line. In addition, disc roll
3a to 3e, 4a to 4e, 5a to 5e, each spacer 6, and optionally the roll shafts 3g, 4g and 5g may be integrally manufactured.

The disc rolls 3a to 3e, 4a to 4e, 5a to 5e constituting the bending rolls 3, 4, and 5 have a diameter such that at least one of the centers of the common circumscribing circles of the disc rolls facing each other is a mill center. It is determined to have a predetermined deviation from the line Y-Y line. For example, in the case of FIG. 3, among the disc rolls of the bending roll 3, the diameters of the disc rolls 3b and 3d (however, 3b> 3d) are different. Set larger than the diameter of the disc rolls 3a, 3c, 3e, and the diameter of the disc rolls 4b, 4d (however, 4b <4d) of the bending rolls 4 is the diameter of the other disc rolls 4a, 4c, 4e. Although the disc roll of the bending roll 5 is not specifically shown, the bending roll 3 or the bending roll 4 is set smaller than
Of the three disc rolls (called roll sets) that are set in the same pattern as any of the above, and are located in the same order counting from the facing inlet side with the mill center line YY line as the center, the inlet side The center of the common circumscribing circle (minimum) of the 2nd and 4th roll sets counted from is the predetermined deviation from the mill center line Y-Y line (however, the second deviation>
A fourth shift amount).

As a result, each bending roll 3,
Three disk rolls (referred to as roll sets), which are positioned in the same order counting from the opposite inlet sides with the mill center line Y-Y line in the center of 4 and 5 as the center, have the center of the common circumscribed circle in the roll axial direction. In, the positions are alternately displaced.

FIG. 4 is an explanatory view showing an arrangement mode of the three disk rolls 3b, 4b, 5b constituting the second roll set counted from the entrance side in the bending rolls 3, 4, 5. In the disk rolls 4b, 4b, 5b, the centers of the disk rolls 3b, 4b, 5b are arranged on the same circumference centered on the mill center line YY.
The diameters of b and 5b are the same, but the diameter of the disk roll 3b is larger than this, and the center O of the common circumscribing circle is displaced by h from the mill center line YY line.

The center O of this common circumscribing circle is on the path line X--X when the metal pipe P passes through, and due to this displacement amount h, the metal pipe P becomes a material when moving forward while rotating in the straightening device. Bending will occur. Such a deviation may be present in at least one place in a plurality (three or more) of roll sets.

The diameter of the minimum common circumscribing circle formed by each roll set may be made substantially equal to the outer diameter of the metal pipe P, but it may be smaller than the diameter of the metal pipe P if necessary. In this case, the deviation amount h gives the bending of the material in the axial direction, while the bending effect of the circumferential direction is further given to enhance the correction effect, and at the same time, the diameter is slightly reduced.

The shift amount h, the position of the roll set having the shift amount h, and the disc roll interval are determined in consideration of the bending size of the metal pipe P, the period, and the like. For example, the distance between the disc rolls can be freely set by changing the width of the spacer 4, and the amount of deviation can be set by changing the disc roll diameter. In addition, in the above-described embodiment, the configuration in which the diameter of one disc roll constituting the roll set is different from the diameters of the other two disc rolls as the deviation imparting means has been described, but three disc rolls constituting the roll set are described. The diameters may be different from each other.

The disk rolls 3a to 3e, 4a to 4e, 5a to 5e constituting the bending rolls 3, 4, and 5 do not necessarily have the same diameter and width, but have substantially the same shape. The roll 3a is shown in FIG. 3 (b). That is, the center portion of the length l having a constant diameter and the end portions 3p, 3q reduced in diameter at angles θ ₁ and θ _{2 respectively} on both sides thereof.
It has and.

The width dimensions of the disc rolls of the bending rolls 3, 4 and 5 are substantially the same except for the disc rolls 3e, 4e and 5e located on the most exit side, and the disc roll 3e located on the most exit side. The width W of each of 4,4e and 5e is made larger than the width of other disk rolls to give an erasing function to spiral marks generated on the surface of the material. This is because the roll shafts 3g, 4g, 5g need to have a short width for each disc roll so as not to become too long and thin in order to ensure bending rigidity, but as a result, spiral marks are likely to occur on the material surface during rotary bending. It is a countermeasure.

In the above embodiment, the number of bending rolls was set to 3 and the number of disk rolls was set to 5. However, if the number of bending rolls is 2 or more, the array of disk rolls should be selected appropriately. It is possible to impart a rotational bending to the material, and the number of disk rolls per bending roll may be at least 3 or more in order to impart bending. When the number of bending rolls is two, the bending rolls are arranged at 180 ° positions around the mill center.

In the straightening device thus constructed, the circular cross-section metal pipe P inserted from the entrance side is repeatedly subjected to rotational bending at a relatively long cycle between the stands arranged in a staggered manner. In Stand II, each of the disc rolls 3a to 3 that compose the bending rolls 3, 4, and 5
e, 4a to 4e, and 5a to 5e are repeatedly rotated and bent at a short cycle between the roll sets to correct the bending.

The outer diameters of the hourglass-shaped rolls of the stands I, III, and IV and the average diameters of the disk rolls 3a to 3e, 4a to 4e, and 5a to 5e constituting the bending rolls 3, 4, and 5 of the stand II are substantially equal, Moreover, all stand I-IV drum-shaped rolls 1,
2. Since the bending rolls 3, 4, 5 are driven at substantially the same number of rotations, the circumferential component Vθ of the roll peripheral speed applied to the metal pipe P is substantially equal, and the bending rolls 3, 4, 5 of the stand II are made of metal. Although the axial velocity component Vx applied to the pipe P is small, the hourglass-shaped rolls 1 and 2 of the stands I, III, and IV impart large axial velocity components Vx to the metal pipe P, resulting in the hourglass-shaped rolls 1 and 2. If you just use a stand
A straightening speed of about 80 to 90% can be obtained.

Since the stand provided with the bending rolls 3, 4, 5 is a stand that is particularly effective for straightening the bend of the pipe end, when this stand is arranged at the most upstream or most downstream, the pipe end is If the roll opening is narrowed in time to pass through the stand and the roll opening is set large when facing the middle part of the pipe and straightening is not performed, the straightening speed is greatly improved. It is possible to In particular, for straightening a pipe to the extent that bending of the pipe end does not pose a problem, high-speed straightening is possible by performing the straightening only with the stand provided with the hourglass roll, excluding the stand provided with the bending roll from the beginning.

In addition, the bending roll 3 of the stand II 3,
For Nos. 4 and 5, it is possible to easily change the pass line for the mill center line YY line by exchanging the disc roll (changing the disc roll diameter). Moreover, since each disc roll has a shape close to a disc, it is easy to manufacture. Even if some disc rolls are damaged such as seizure, other disc rolls can be continuously used by replacing only this disc roll.

In the above-mentioned embodiment, the metal pipe is shown as the straight member having a circular section for straightening, but it goes without saying that the bending can be straightened even for a solid round bar. Further, in the above-mentioned embodiment, the hourglass rolls 1 and 2 of the stands I to IV and the bending rolls 3, 4 and 5 are all driven to rotate, but only the hourglass rolls 1 and 2 of the stands I, III and IV are provided. Drive the stand II bending rolls 3, 4,
5 may not be driven. With such a configuration, the straightening speed is slightly reduced, but the equipment is compact and the equipment cost can be reduced.

Further, in the above-described embodiment, the structure provided with the hourglass-shaped rolls 1 and 3 is three, and the stand provided with the bending roll is one, but at least two stands are provided with the hourglass-shaped roll. At least one stand equipped with a base and a bending roll is sufficient.

FIG. 5 is an explanatory view corresponding to FIG. 4, showing another example of the bending roll. In this example,
For example, the three disc rolls 13b, 14b, 15b that form the second roll set from the entrance side have the same diameter, but the center of each disc roll 13b, 14b, 15b is the roll shaft 13g, 14g, 15g.
It is configured such that it is decentered by an appropriate amount from the center of. The other configurations and operations are substantially the same as those shown in FIGS. 2 and 3, and the description thereof will be omitted. Also in this case, as in the case of the example shown in FIG. 3, the material pass line XX line can be displaced from the mill center line YY line, and the same effect can be obtained.

FIG. 6 is a side view corresponding to FIG. 3 (a) showing still another example of the bending rolls. In this example, three bending rolls 23 and 24 (only two are shown in the drawing). The number of disk rolls that make up each is different. That is, the patterns of the disc rolls 23a to 23e in the bending roll 23 are the same as the disc roll pattern of the bending roll 3 shown in FIG.
The pattern is the same as that of the bending roll 4 shown in FIG. 3 in which the second disk roll 4b from the entrance side is omitted.

With such a structure, when the contact surface pressure between the material and the disk roll located on the side where the pass line is convex in each roll set is substantially zero, it does not participate in the substantial straightening function. There is no problem even if the disk roll whose contact surface pressure is zero is omitted, and rather, the omission of the disk roll contributes to the reduction of the tool cost. Therefore, in the example of FIG. 6, the disc roll 24d can be omitted. The other configurations and operations are substantially the same as those shown in FIGS. 2 and 3, and the description thereof will be omitted.

FIG. 7 (a) is a side view corresponding to FIG. 3 (a) showing still another example of the bending rolls, and three bending rolls 33, 34 (only two of them are shown in the drawing). Are set such that the roll shafts 33g and 34g are crossed by .gamma. And are inclined such that the entrance ends approach the mill center line Y--Y line side. Also each venting roll 33,3
4 disk rolls 33a to 33e, 34a to 34e
Although the diameter and width are different, the shape is substantially the same. As a representative example of the disk roll 33a, as shown in FIG. 7 (b), the central portion and both end portions 33p and 33q are both frustoconical.
Is equipped with. Other configurations and operations are substantially the same as the examples shown in FIGS. 2 and 3, and the description thereof will be omitted.

FIG. 8 is a side view corresponding to FIG. 7 (a) showing still another example of the bending roll. In this example, FIG.
The configuration is the same as the configuration in which the second disk roll 34b from the entrance side that constitutes the bending roll 34 of the example shown in (a) is removed. By removing unnecessary disc rolls, tool costs can be reduced. Other configurations and operations are substantially the same as in the case of the example shown in FIG. 7, and corresponding parts are designated by the same reference numerals and description thereof is omitted. In the case of this embodiment, the disc roll 34d can be omitted.

FIG. 9 is a side view showing another shape of the disk roll, and FIG. 9 (a) shows that both ends of the central portion having the same diameter have arcuate surfaces having curvature radii R ₁ and R ₂ , respectively. Has been formed. Further, FIG. 9 (b) is formed so as to have an oval shape as a whole in a side view (the circumferential surface is an arc having a radius of curvature R ₃ ).

Even if such a disc roll is used, FIG.
Of course, the same effects as those of the disk roll having the shape shown in FIGS. 7B and 7B can be obtained. Although the shape becomes complicated, the cross-sectional shape of the roll viewed on a plane perpendicular to the roll axis, that is, the cross-sectional shape of the roll in a front view may be an arbitrary closed curve shape, for example, an ellipse, instead of a perfect circle. Next, a comparative test between the device of the present invention and the conventional device will be described with specific numerical values.

(Test Example 1) A carbon steel pipe having a diameter of 190 mm, a length of 10 m, and a wall thickness of 15 mm obtained by the Mannesmann pipe manufacturing method was used, and the apparatus of the present invention shown in FIGS. 2 to 4 and FIG. Straightening was performed by applying a straightening machine (comparative example) composed of only one stand II, and the straightness of the pipe end and the pipe middle and the average straightening speed were detected.

The dimensions of the device of the present invention are as follows. (Stands I, III, IV) Number of drum-shaped rolls: Two drum-shaped rolls Inclination angle: 30 ° Number of drum-shaped rolls: 100 rpm Maximum diameter of drum-shaped rolls: 400 mm Minimum diameter of drum-shaped rolls: 350 mm Body-shaped roll body length: 700 mm

(Stand II) Number of bending rolls: 3 Bending roll inclination angle: 10 ° Bending roll rotation speed: 100 rpm Bending roll configuration disc roll number: 5 / axis Disc roll diameter: 350 mm to 380 mm Disc roll width: 100 mm ( Final stage disc roll width only
(150 mm) (The amount of deviation h between the center of the common circumscribing circle of each roll set and the path center line is 4.0 mm, −2.0 mm, 1.0 mm for the 2nd, 3rd, and 4th roll sets from the entrance side, respectively. Both 1 and 5 roll set were 0.) Spacer: Diameter 300mm, width 50mm Number of spacers: 4 pieces / axis

The results are shown in Table 1.

[0045]

As is apparent from Table 1, in the device of the present invention, the whirling of the pipe is prevented in the middle portion of the pipe, and effective repetitive bending is applied between the stands. Also improved. On the other hand, it can be seen that the straightening speed of the device of the present invention is almost three times higher than that of the comparative example.

(Test Example 2) Among the disk rolls constituting the second roll set from the entrance side of each bending roll in the stand II, the disk roll having the convex pass line is a disk having a diameter of 300 mm and a width of 100 mm. When the roll was replaced and the same straightening was carried out, the straightening speed and straightness almost equal to those of Test Example 1 were obtained.

(Test Example 3) In the apparatus of the present invention as shown in FIG. 1, the bending rolls 3, 4, and 5 of the stand II were used.
Was separated from the drive source, and correction was performed in a free rotation state. As a result, the straightening speed was slightly lowered to 700 mm / sec, but the straightness was almost the same as in the case of Test Example 1, and the stable straightening work could be performed.

[0049]

As described above, in the apparatus of the present invention, the bending of the end portion and the bending of a short period of the hollow or solid long member having a circular cross section are made without enlarging the roll and stand equipment. The present invention has excellent effects such as the ability to reliably correct and to correct at high speed.

[Brief description of drawings]

FIG. 1 is a schematic side view of a device of the present invention.

FIG. 2 is a front view of the bending roll of the stand II shown in FIG. 1 viewed from the entrance side.

3 is a side view of the disc roll taken along the line III-III of FIG. 2 and a side view of the disc roll.

FIG. 4 is an explanatory view showing a roll arrangement mode of a roll set second from the entrance side.

FIG. 5 is an explanatory diagram showing a roll arrangement mode of a second roll set in another example of the bending roll.

FIG. 6 is a view of yet another example of a bending roll.
It is a side view corresponding to (a).

FIG. 7 shows another example of a bending roll.
It is a side view corresponding to (a) and FIG.3 (b).

FIG. 8 is a view of yet another example of a bending roll.
It is a side view corresponding to (a).

FIG. 9 is a side view showing another shape of the disc roll.

FIG. 10 is a schematic view showing a conventional straightening machine.

FIG. 11 is a schematic view showing another conventional straightening machine.

[Explanation of symbols]

1,2 drum roll 3,4,5 bending roll 3a, 3b ~ 3e Disc roll 4a, 4b ~ 4e Disc roll 5a, 5b ~ 5e Disc roll 6 spacers P metal tube 13,14,15 Bending roll 23,24 Bending roll 33,34 Bending roll

Claims (2)

[Claims] 1. A plurality of bending rolls in which at least three or more disk rolls are arranged at intervals in the axial direction, are arranged so as to be inclined or inclined and crossed around a mill center line, At least one stand of the common circumscribing circle centers for the disk rolls facing each other of the bending rolls, at least one center being eccentric with respect to the mill center line;
A bend straightening device for a long member having a circular cross section, wherein a plurality of stands provided with concave rolls are arranged in a line. 2. The bending roll is a mill center.
2. The bending correction apparatus for a long member having a circular cross section according to claim 1, wherein at least one of the disk rolls forming the common circumscribing circle having an eccentric center with respect to the line is removed.