JP2003136104A - Rolling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling device capable of omitting die changes and shortening change times of the pass schedule and capable of decreasing rolling roll pairs by incorporating a rolling unit having three-gang rolling pairs into the tail end, at the same time. SOLUTION: The rolling device is provided with a mechanical reduction (accelerating) gear machine 9 to output from the output shafts 9d, 9e by dividing the output of a motor 8 with each different change gear ratio and rolling units 6, 7 and 14 having two or three-gang rolling roll pairs and a second power transmission means to input motive energy divided by the mechanical reduction (accelerating) gear machine 9 from the input shafts and to distribute the energy to rolling roll pairs by each different change gear ratio. One or two rolling roll units is/are chosen from the rolling units 6, 7 and 14, and the input shaft of the second power transmission means of the rolling unit is connected with the output shaft 9d or 9e.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling apparatus for high-speed finishing of steel strips such as wire rods. More specifically, it realizes omission of setup change and reduction of time, rolling steel strips with high dimensional accuracy, and performing same rolling. The present invention relates to a rolling device capable of continuously adjusting the diameter of a steel strip by continuously changing the reduction amount using a roll pair.

[0002]

2. Description of the Related Art A wire rod and a steel bar such as a steel bar are subjected to required rolling through a row of rough rolling mills, a row of intermediate rolling mills, and a row of finish rolling mills. When rolling the bar steel into a predetermined shape and dimension, a plurality of rolling roll pairs having a hole shape (caliber) formed between the rolls are arranged along the pass line of the bar steel so that the cross-sectional area of the bar gradually becomes smaller. A pass schedule is adopted.

As a finish rolling mill capable of performing high-speed rolling without imparting twist to the bar steel, it has a drive source such as one or a plurality of motors, and has a distance between passes (of two adjacent rolling roll pairs). There is a block rolling mill having a short distance (rotary shaft center distance) of, for example, 1000 mm or less, in which the roll rotation speed ratio of each rolling roll pair is fixed by a transmission means such as a gear. As this block rolling mill, Morgan's No Twist Mill (NTM), (UK) Kavana's Twist Free Finishing Mill, (Italy)
High-speed finishing mills manufactured by Danieli are known.

FIG. 3 is a schematic diagram showing the structure of a typical block rolling mill. In this block rolling mill, pairs of rolling rolls 31, 32, 33, 34 are arranged along the pass line, and the pairs of rolling rolls adjacent to each other are arranged so that the axes thereof are offset by 90 degrees. There is. Each rolling roll pair 31, 32, 33, 34 is driven by a motor 35, and the output of the motor 35 is a gear reduction (increasing) speed reducer 36, 3
Rolling roll pairs 31, 32, respectively via 7, 38, 39
A common drive system that is distributed to 33 and 34 is adopted, and the gear ratio (gear ratio) is fixed.

Generally, the area reduction rate of each pass is set to about 20%, and the hole types of the rolling roll pairs 31, 32, 33, 34 are oval, round, oval, and round, respectively, and have the same entry. Finishing dimensions obtained for side dimensions are
Determined by round pass type of final pass. FIG. 4 is a schematic view showing an oval hole type. As shown in FIG.
The oval hole type has an arc, and the groove width b of the hole type is the vertical dimension h.
It is formed to be 1.5 times or more. Figure 5
It is a schematic diagram which shows a round hole type. As shown in FIG. 5, the round hole type has a relief portion of a predetermined angle θ or less and a bottom portion of the hole die other than the relief portion and a perfect circular portion formed of an arc of a radius r. Groove width b is 1.5 of vertical dimension h
It is formed to be less than double.

[0006] In this conventional block rolling machine, when changing the finishing dimension, it is necessary to perform setup change in order to change the hole die, and stepless continuous rolling (size-free rolling) for continuously adjusting the diameter of the bar steel is required. ) Was impossible to implement.

A reducing sizing mill developed by Morgan as a block rolling machine capable of performing size-free rolling by shortening set-up change time and performing precision rolling of rolled steel with high dimensional accuracy. (RSM) and Compact Sizing Mill (CS
There is M). FIG. 6 is a schematic diagram showing the RSM. In this RSM, rolling roll pairs 41 and 42 and rolling roll pairs 43 and 44 are provided in rolling units 45 and 46, respectively. The rolling units 45 and 46 can be automatically installed in the pass line. The hole types of the rolling roll pairs 41, 42, 43, 44 are oval,
Round, round, round. The output of the motor 47 is passed through a gear ratio changing unit 48 including a large number of gears and gear changes to each rolling roll pair 41, 4 and 4.
It is configured to be divided into 2, 43 and 44.

In this RSM, the rolling unit 46
Since both of the roll types of the rolling rolls 43 and 44 provided in the above are round hole types, precision rolling can be realized, and the rolling units 45 and 46 in which the rolling roll pairs are incorporated in advance are incorporated into the pass line to perform the setup change. The time can be shortened. Then, the gear ratio changing unit 48
By changing the gear ratio by changing the area reduction rate,
It becomes possible to perform size-free rolling. However, in this RSM, since the gear ratio changing unit 48 includes a large number of gears, there is a problem that the structure becomes complicated and the apparatus becomes expensive.

Further, since the CSM is a rolling machine exclusively used for sizing rolling, the surface reduction rate of the final two pairs of rolling rolls is low, so that the quality of the product can be ensured, the pass schedule can be reduced, and the like. There is a problem in that a rolling mill is required to increase the surface ratio, and as a result, the structure is similar to that of RSM.
As a drawback of both RSM and CSM, since the final two pairs of rolling rolls are round type having substantially the same shape for sizing, the rolling rolls for reducing the surface before rolling with these two pairs of rolling rolls There is a problem that many pairs are required, and finally the number of rolling roll pairs is increased and the running cost is increased.

The inventors of the present invention used a 4-stand block rolling machine having a speed increase ratio between rolling roll pairs of 1.25 and a pass-to-pass distance of 800 mm to make the fourth pass an empty pass,
The dimensional accuracy of the product when the hole type of the second pass and the third pass is oval, round, and round, and the roll interval (gap) is adjusted so that the surface reduction rate of each of the first and second passes is 20%. Examined. FIG. 7: is a schematic diagram which shows the structure of the block rolling mill in this case. In the figure, the same parts as those in FIG. 3 are designated by the same reference numerals. In the block rolling machine of FIG. 7, it was found that dimensional accuracy of ± 0.1 mm and eccentric diameter difference of 0.2 mm or less can be achieved in the product size range of 5.5 to 18 mmφ. In addition, when the roll gap was adjusted and the size-free range was examined in the product size of 5.5 to 18 mmφ, the range in which the dimension crossing ± 0.2 mm and the deviation diameter difference within 0.3 mm can be achieved is the rolling roll pair 32 and It was found that when the distance between passes with the roll pair 33 was 800 mm, it was about 0.2 mm with respect to the round hole type, but when the distance between passes was shortened to 150 mm, it was found to be 0.4 mm. this is,
It is considered that by shortening the distance between passes, it was possible to prevent disturbance such as falling during rolling. Therefore,
High reduction rate rolling and sizing rolling are performed in one rolling unit, and by adjusting the roll gap and the distance between passes, precision rolling and size-free rolling are realized even if the number of rolling roll pairs is reduced from 4 to 3. It turns out that you can do it.

The present invention has been made in view of the above circumstances, and is provided with a plurality of rolling units having two or three pairs of rolling rolls so as to be incorporated according to the size of the product and the type of rolling. By changing the type and number of rolling units, setup change can be omitted, the time for changing the pass schedule can be shortened, and a rolling unit having three pairs of rolling rolls can be incorporated at the end. Then, it aims at providing the rolling mill which can reduce a running cost by reducing the number of rolling rolls.

It is another object of the present invention to provide a rolling device which is equipped with a desorption device which uses a hydraulic cylinder as a driving force to enable quick change of the rolling unit.

Further, in the present invention, the hole type of the three rolling roll pairs is oval, round, or round, and the roll gap of each rolling roll pair can be adjusted separately, and the second and third stations can be adjusted. By providing a rolling unit with a shorter distance between the rolling rolls and the rolling rolls, it is possible to perform precision rolling by incorporating this at the end of the rolling unit, and it is possible to carry out size-free rolling in a wide range, as well as rolling rolls. It is an object of the present invention to provide a rolling mill capable of reducing the logarithm and running cost.

Further, according to the present invention, by making the roll diameter of the third rolling roll pair of the rolling unit smaller than the roll diameter of the other rolling roll pair, the rolling roll pair between the second rolling roll and the third rolling roll is It is an object of the present invention to provide a rolling mill that can further reduce the distance, prevent disturbance, and further widen the size-free range.

According to the present invention, the third rolling roll pair of the rolling unit, together with the first and second rolling roll pairs, is configured to distribute the power by the power transmission means. An object of the present invention is to provide a rolling apparatus having a simpler structure as compared with the case where a pair of rolling rolls in a row is driven independently.

[0016]

The rolling apparatus of the first invention is
In a rolling mill equipped with a block rolling machine in which two or more rolling roll pairs are arranged along the path line of the steel strip with the axes of the adjacent rolling roll pairs deviated by 90 degrees, the output of the driving means is changed. First power transmission means for dividing the power into a plurality of powers with different gear ratios and outputting the respective powers from the output shaft, two or three pairs of rolling rolls, and at least the first from the upstream side of the pass line. And a plurality of rolling units having second power transmission means for inputting the power split by the first power transmission means from the input shaft to the second rolling roll pair and distributing the power at different speed ratios. One or a plurality of rolling units is selected, and the input shaft of the second power transmission means of the rolling unit is to be attached / detached to / from the output shaft for outputting the predetermined power divided by the first power transmission means. It is characterized by That.

According to the first aspect of the invention, the type and number of rolling units incorporated in the apparatus can be easily changed according to the size of the product and the type of rolling such as normal rolling, precision rolling and size-free rolling. You can change the pass schedule. Therefore, the setup change for changing the hole type can be omitted, and the time for changing the pass schedule can be shortened. Furthermore, by incorporating a rolling unit having three pairs of rolling rolls at the end,
The number of pairs of rolling rolls for finish rolling can be reduced from the conventional four to three, and the running cost can be reduced.

A rolling apparatus according to a second aspect of the present invention is characterized in that, in the first aspect of the present invention, a hydraulic cylinder is used as a driving force, and an attaching / detaching apparatus for attaching / detaching the rolling unit is provided. Second
In the invention, a quick change of the rolling unit is possible.

The rolling apparatus of the third invention is the rolling apparatus of the first or second invention, which has three pairs of rolling rolls, and the hole shape of each rolling roll pair is an oval, round or round from the upstream side of the pass line. The distance between the rolling roll pairs of the second and third stations is shorter than the distance between the rolling roll pairs of the first and second stations, and the roll gap of each rolling roll pair is It is characterized by comprising a rolling unit adapted to be adjusted separately.

In the third aspect of the invention, when the rolling unit is incorporated at the tail end, high reduction of area rolling can be carried out with the first and second rolling pairs, and the second and third rolling pairs can be carried out. Since the holes of the pair of eye rolling rolls are both round, precision rolling can be performed, and one rolling unit has the characteristics of high reduction-ratio rolling and sizing rolling. Further, by changing the roll gap and steplessly changing the reduction amount, it is possible to easily carry out size-free rolling in which the diameter of the steel strip is adjusted steplessly. Since the distance between the pair of rolling rolls at the second and third stations is shortened, disturbance such as falling over during rolling can be prevented and the size-free range can be widened. Therefore, it is possible to reduce the number of rolling rolls while ensuring a sufficiently high dimensional accuracy and a wide size-free range.
Running costs can be reduced.

A rolling apparatus of a fourth invention is characterized in that, in the third invention, the roll diameter of the third rolling roll pair of the rolling unit is smaller than the roll diameter of the second rolling roll pair. To do. In the fourth invention, the second and third
The distance between the rolling roll pair and the seam can be further shortened, disturbance can be prevented, and the size-free range can be further widened.

According to the rolling apparatus of the fifth aspect of the invention, in the third or fourth aspect of the invention, the rolling roll pair in the third rolling unit of the rolling unit is configured to distribute the power by the second power transmission means. Characterize. In the fifth invention, 3
Compared with the case of individually driving the rolling roll pair of the continuous line,
The structure is simple and the dimensional accuracy of the bar steel is good.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a schematic diagram showing a rolling device according to an embodiment of the present invention. In this rolling apparatus, a rolling unit 6 and a rolling unit 7 are arranged along a pass line of a steel strip, and a pair of rolling rolls 1 and 2 provided in the rolling unit 6 and rolling provided in the rolling unit 7. Roll pairs 3, 4, and 5 are sequentially arranged side by side. The rolling roll pairs 1, 3 and 5 are arranged in a state in which the directions of the axes thereof are in the horizontal direction and orthogonal to the pass line, and the rolling roll pairs 2 and 4 are arranged.
Are arranged with their axial directions aligned with the vertical direction. Therefore, the axis of the two adjacent pairs of rolling rolls is deviated by 90 degrees.

The hole types of the rolling roll pairs 1 and 2 are oval and round, respectively. The hole types of the rolling roll pairs 3, 4 and 5 are oval, round and round, respectively, and the hole types of the rolling roll pair 4 and the rolling roll pair 5 have the same shape and substantially the same size. The distance between the rolling roll pair 4 and the rolling roll pair 5 is set as short as possible by reducing the roll diameter of the rolling roll pair 5.

In the gear reduction (increasing) speed reducer 9 as the first power transmission means, the gear 9a is integrally rotatably provided at the end of the output shaft 8a of the motor 8, and the gears are provided on both sides of the gear 9a. 9b and 9c are meshed. Gears 9b and 9
Output shafts 9d and 9e are provided at c, respectively, and the output of the motor 8 is divided by different gear ratios (gear ratios) and output from the output shafts 9d and 9e.
An input shaft 6b of the rolling unit 6 is connected to the output shaft 9d via a connecting portion 6a. A gear 6c is integrally rotatably provided at an end of the input shaft 6b, and gears 6d and 6e are meshed with both sides of the gear 6c. The connecting portion 6a, the input shaft 6b, the gears 6c, 6d and 6e constitute second power transmission means, and the power input from the input shaft 6b is divided by different gear ratios, and is rolled with the rotation of the gear 6d. One roll of the roll pair 1 rotates, and one roll of the rolling roll pair 2 rotates with the rotation of the gear 6e.

The input shaft 7b of the rolling unit 7 is connected to the output shaft 9e via a connecting portion 7a. Input shaft 7b
A gear 7c is integrally rotatably provided at the end of the
Gears 7d and 7e are engaged with both sides of the gear 7c,
The gear 7e is meshed with the gear 7f, and the gear 7f is engaged with the gear 7f.
g is meshed. Connecting portion 7a, input shaft 7b, gear 7
c, 7d, 7e, 7f and 7g constitute the second power transmission means, the power input from the input shaft 7b is divided by different gear ratios, and one of the rolling roll pairs 3 is rotated by the rotation of the gear 7d. Of the rolling roll pair 4 rotates as the gear 7e rotates, and one roll of the rolling roll pair 5 rotates as the gear 7g rotates. In addition, a roll gap is adjusted by moving a stand (not shown) rotatably provided with the other of the rolling roll pairs 3, 4 and 5 by a moving means (not shown). Has been done.

The rolling unit 6 and the rolling unit 7 can be freely attached / detached to / from the output shafts 9d, 9e via the connecting portions 6a, 7a. This attachment / detachment device (not shown) uses a hydraulic cylinder or the like as a driving force. Done by. Therefore, it is possible to perform a quick change from the rolling unit 7 having the pair of rolling rolls to the rolling unit 14 having the pair of rolling rolls 12 and 13.

In the rolling unit 14, the input shaft 14
A gear 14c is integrally rotatably provided at the end of b, and gears 14d and 14e are meshed with both sides of the gear 14c. Then, the rolling unit 14 outputs the output shaft 9e.
When one of the rolling roll pairs 12 is rotated, the one roll of the rolling roll pair 12 is rotated with the rotation of the gear 14d, and one roll of the rolling roll pair 13 is rotated with the rotation of the gear 14e. There is.

In this embodiment, when precision rolling and size-free rolling are carried out, the rolling unit 7 having three pairs of rolling rolls is incorporated, and when carrying out normal rolling, the rolling unit is carried out. The roll gap of the third rolling roll pair 5 of No. 7 is made wider than a predetermined size, or the rolling unit 7 is incorporated into the rolling unit 14 having two rolling roll pairs by quick change. The cavities of the pairs of rolling rolls 12 and 13 of the rolling unit 14 are either oval, round or round, depending on the size of the product and the desired degree of rolling.

When the rolling unit 7 is incorporated at the tail end of the apparatus, when the roll gaps of the rolling roll pairs 3 and 4 are adjusted so that the area reduction rate is 20%, the product size is 5.5. Dimensional accuracy ± 18 mmφ
It was confirmed that it was possible to achieve 0.1 mm and a difference in eccentricity of 0.2 mm. Further, when the distance between the rolling roll pair 4 and 5 is set to 150 mm, by appropriately adjusting the roll gap, in the product size of 5.5 to 18 mmφ, the size free range is 0.4 mm and the dimensional accuracy is ± 0.2 mm. It was confirmed that the deviation diameter difference within 0.3 mm could be achieved.

FIG. 2 is a schematic diagram showing a state in which one rolling unit 16 is incorporated in the rolling apparatus according to the embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. The rolling unit 16 has a structure similar to that of the rolling unit 6, and includes rolling roll pairs 18 and 19, and a connecting portion 16a as a second power transmission means, an input shaft 16b, and gears 16c, 16d and 16e. Depending on the size of the product, it may be necessary to incorporate only one rolling unit in the pass schedule, and in this case, the rolling unit 16 including two pairs of rolling rolls is used for finish rolling. The profile of the rolling roll pairs 18 and 19 is either oval, round or round, or round, depending on the size of the product and the desired degree of rolling.

When carrying out precision rolling and size-free rolling, the rolling unit 16 is replaced with a rolling unit 17 having three rolling roll pairs. The rolling unit 17 has a structure similar to that of the rolling unit 7, and includes pairs of rolling rolls 20, 21 and 22, a connecting portion 17a as a second power transmission means, an input shaft 17b, gears 17c, 17d, 1 and 1.
7e, 17f and 17g. Rolling roll pair 2
Pore types 0, 21 and 22 are oval, round and round.

As described above, in the rolling apparatus of the present invention, the type and number of rolling units to be incorporated in the apparatus are set according to the size of the product and the type of rolling such as normal rolling, precision rolling and size-free rolling. By changing it, the pass schedule can be easily changed.
Therefore, the setup change for changing the hole type can be omitted, and the pass schedule changing time can be shortened.

Further, when the rolling unit 7 or 17 having three pairs of rolling rolls is arranged as the finish rolling, the number of rolling rolls can be reduced while ensuring a sufficiently high dimensional accuracy and a wide size free range. Therefore, the running cost can be reduced compared to the case where four pairs of rolling rolls are arranged as the conventional finish rolling.

The surface reduction rate of each rolling roll pair and the distance between the rolling roll pairs 4 and 5 of the rolling unit 6 are not limited to those described in the above-mentioned embodiment, but may be changed depending on the product size or the like. Can be changed.
In the above embodiment, the case where the third rolling roll pair 5 is connected to the second rolling roll pair 4 so as to rotate at a predetermined gear ratio has been described, but the present invention is not limited to this. Alternatively, the third rolling roll pair 5 may be independently driven, or may be mounted so as to be freely rotatable without being driven. However, if the third rolling roll pair and the second rolling roll pair are commonly driven, the structure of the device becomes simpler.
Good dimensional accuracy.

Further, in the above embodiment, the case where two rolling units are incorporated in the rolling apparatus has been described, but the present invention is not limited to this, and three or more rolling units may be incorporated. Good.

[0037]

As described above in detail, in the case of the first invention, the rolling unit incorporated in the apparatus is adapted to the size of the product and the type of rolling such as normal rolling, precision rolling and size-free rolling. The pass schedule can be easily changed by changing the type and number.
Therefore, the setup change for changing the hole type can be omitted, and the time for changing the pass schedule can be shortened. Further, by incorporating a rolling unit having three rolling roll pairs at the end, the number of rolling roll pairs can be reduced from the conventional four rolling rolls to three rolling rolls, and the running cost can be reduced.

In the case of the second invention, since the desorption device having the hydraulic cylinder as the driving force is provided, the quick change of the rolling unit is possible.

In the case of the third aspect of the invention, by incorporating a rolling unit having three pairs of rolling rolls at the tail end, high reduction of area rolling can be carried out by the first and second rolling roll pairs. Since the hole shapes of the second and third rolling roll pairs are both round, precision rolling can be performed. Further, by changing the roll gap and steplessly changing the reduction amount, it is possible to easily carry out size-free rolling in which the diameter of the steel strip is adjusted steplessly. Since the distance between the pair of rolling rolls at the second and third stations is shortened, disturbance such as falling over during rolling can be prevented and the size-free range can be widened.
Therefore, the number of rolling rolls can be reduced while sufficiently high dimensional accuracy and a wide size-free range are secured, and the running cost can be reduced.

In the case of the fourth invention, the rolling unit 3
Since the roll diameters of the rolling roll pairs of the continuous rolls are made smaller than the roll diameters of the other rolling roll pairs, the distance between the rolling roll pairs of the second and third rolls can be further shortened, and the disturbance This can be prevented and the size free range can be further widened.

In the case of the fifth invention, the rolling unit 3
Since the rolling roll pair of the third station is configured to distribute the power by the power transmission means together with the rolling roll pairs of the first and second stations, it is possible to independently drive the third rolling roll pair. In comparison, the structure of the device is simplified and the dimensional accuracy of the steel strip is improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a rolling device according to an embodiment of the present invention.

FIG. 2 is a rolling device according to an embodiment of the present invention,
It is a schematic diagram which shows the state which incorporated one rolling unit.

FIG. 3 is a schematic diagram showing a configuration of a typical block rolling mill.

FIG. 4 is a schematic view showing an oval hole type.

FIG. 5 is a schematic view showing a round hole type.

FIG. 6 is a schematic diagram showing RSM.

FIG. 7 is a schematic view showing a state where the fourth pass is an empty pass in the 4-stand block rolling mill.

[Explanation of symbols]

1, 2, 3, 4, 5 Roll pair 6 rolling unit 6a connecting part 6b Input shaft 6c, 6d, 6e gears 7 Rolling unit 7a connection part 7b Input shaft 7c, 7d, 7e, 7f, 7g Gears 8 motor 8a Output shaft 9 Gear reduction (increasing) speed machine 9a, 9b, 9c gears 9d, 9e Output shaft

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Kuroda             Fukuoka Prefecture Kitakyushu City Kokurakita-ku, Konomi-cho 1-share             Ceremony Company Sumitomo Metal Kokurauchi (72) Inventor Takashi Kuboki             Fukuoka Prefecture Kitakyushu City Kokurakita-ku, Konomi-cho 1-share             Ceremony Company Sumitomo Metal Kokurauchi F term (reference) 4E002 AC12 AC14 BC01 CA19 CB08                 4E024 AA11 DD19 EE10

Claims (5)

[Claims] 1. A rolling mill equipped with a block rolling machine, in which two or more rolling roll pairs are arranged along a pass line of a rolled steel with the axes of adjacent rolling roll pairs deviated by 90 degrees. The output of the means is divided into a plurality of powers at different gear ratios, the first power transmission means for outputting each of the divided powers from the output shaft, two or three pairs of rolling rolls, and at least the upstream of the pass line. From the side to the first and second rolling roll pairs,
A plurality of rolling units having second power transmitting means for inputting the power split by the first power transmitting means from an input shaft and distributing at different gear ratios, and selecting one or a plurality of rolling units. Then, the rolling mill is characterized in that the input shaft of the second power transmission means of the rolling unit is attached to and detached from the output shaft which outputs the predetermined power divided by the first power transmission means. 2. The rolling apparatus according to claim 1, further comprising a detaching device for detaching the rolling unit, using a hydraulic cylinder as a driving force. 3. A rolling roll pair having three rolling roll pairs, wherein the hole shape of each rolling roll pair is an oval, a round, or a round from the upstream side of the pass line, and between the rolling roll pairs of the second rolling roll and the third rolling roll. Is arranged in a state in which the distance between the rolling rolls is shorter than the distance between the first and second rolling roll pairs, and the rolling gap of each rolling roll pair is individually adjusted. The rolling apparatus according to 1 or 2. 4. The rolling apparatus according to claim 3, wherein the roll diameter of the third rolling roll pair of the rolling unit is smaller than the roll diameter of the second rolling roll pair. 5. The rolling apparatus according to claim 3, wherein the third rolling roll pair of the rolling unit is configured to distribute the power by the second power transmission means.