KR101461847B1 - Method for Cooling Work Roll - Google Patents

Abstract

A rolling roll cooling method is provided.
A first cooling means provided on at least one side of the rolling roll and a second cooling means provided adjacent to the first cooling means to enable centralized cooling of the rolling roll corresponding to continuous rolling of a rolling material having a rolling gap or a similar width, A rolling roll cooling method for cooling a rolling roll through a rolling roll cooling device including a first cooling means provided on the upper side and a lower side based on the first cooling means for providing additional cooling of the rolling roll, A main cooling step of injecting cooling water corresponding to the width of the material; And a concentrated cooling step of injecting cooling water to a portion corresponding to a widthwise center portion of the rolled material through the second cooling means.

Description

Method for Cooling Work Roll}

The present invention relates to a rolling roll cooling apparatus, and more particularly, to a rolling roll cooling apparatus which improves the cooling method of a roll, particularly a work roll contacted with a hot rolled material, so that the thermal expansion of the rolling roll, And more particularly, to a rolling roll cooling method which, when rapidly increasing, realizes centralized cooling of the rolling roll, thereby preventing thermal cracking of the rolling roll, and ultimately improving the cooling efficiency of the rolling roll, thereby contributing to the rolling quality.

In FIG. 1, a hot rolling process is shown. For example, the material 220 extracted from the heating furnace 210 is rolled through the width extruding and extruding rolls 230 and 240, and the thus rolled plate (thick plate) is fed to the preliminary straightener 250 Processed by the accelerating cooler 260, and passed through the hot-calibrator 270. In this case, in the case of FIG. 1, the hot rolling state of the thick plate material, that is, the thick plate is shown.

Referring to FIG. 7, there is shown a rolling machine, which is a main facility for hot rolling, as is known in the art. The rolling machine includes a pair of rollers 130, A back-up roll 120, and a work roll 130. The back-

FIG. 2 shows the cooling state of the work roll 130 during hot rolling using such a rolling mill.

That is, in the vicinity of the work roll 130 at the time of rolling, cooling water is injected through the nozzle 150 to implement work roll cooling, since the work roll is in continuous contact with the hot rolled material (plate) 140, And is supported by the backup roll 120 while being cooled by the cooling water.

At this time, as shown in FIG. 2, the cooling water is collected to the downstream side of the cooling water injection of the work roll to prevent the deformation such as the occurrence of warpage of the material during rolling due to the uniform cooling inhibition of the rolling material 140 160 may be provided.

On the other hand, in FIG. 3, the result of simulating the time-dependent thermal expansion and cooling cycle from the viewpoint of the influence of the contact of the hot rolled plate 140 of the work roll 130 during hot rolling and the influence of cooling water, FIG.

3, the surface temperature of the work roll 130 during hot rolling appears in the form of a sawtooth wave. This is because when the temperature rises at the moment of contact with the hot rolled plate during rolling, the temperature of the roll falls to be.

On the other hand, as shown in Fig. In general, a single cooling water nozzle 150 is generally disposed on the inlet side and the outlet side of the work roll 130 during the conventional hot rolling.

Of course, the cooling water jetted through the cooling water nozzle 150 can adjust the spraying width corresponding to the width of the rolling material (plate) 140.

Therefore, in the conventional work-roll cooling as shown in Fig. 2, cooling control according to a simple facility structure for controlling the cooling effect through variable cooling in the longitudinal direction of the work roll 130, There was a problem that it was not.

For example, when the rolling material 140 having the same width as the rolled material 140 is continuously rolled in the rolling mill, not only the width of the rolled plate but also the rolling roll, particularly only a specific portion of the work roll, There is a problem that the thermal expansion of the work roll due to sufficient cooling can not be reduced by the conventional cooling nozzle alone.

That is, the conventional rolling roll cooling system as shown in Fig. 2 has a limitation in suppressing excessive thermal expansion of the work roll and occurrence of thermal cracks when the hot rolled plate of the same width is continuously rolled, Before the rolls are replaced, only the high-temperature rolling material (rolled plate) having a narrow width for a certain period of time is concentrated and rolled, resulting in the above-described problem further.

Therefore, in the conventional case, since it can not cope with the thermal expansion of the work roll through the cooling spray, thermal cracks are generated when the thermal expansion of the work roll increases sharply and adversely affects the rolling quality of the rolled plate, Because it has to be replaced sooner or sooner.

In addition, it causes a lot of cost increase such as input of an operator due to the roll change, stoppage of the rolling mill, or rolling of the rolled roll.

For example, during hot rolling of the rolled material 140, that is, the rolled plate (heavy plate), the work roll 130 is in contact with high-temperature materials at about 1000 ° C. or higher, rolling plates of various thicknesses and widths, In order to improve productivity, there is a tendency to reduce the non-rolling time without rolling. Therefore, as the running time of the rolling mill increases, the rolling contact time of the work roll is further increased and the interval of rolling mill rolling is gradually narrowed.

Therefore, although a problem of rapid thermal expansion of the work roll which contacts with the hot rolled plate for a long time has occurred in recent years, it is difficult to appropriately cope with the thermal expansion of the work roll in the conventional manner as shown in Fig.

Particularly, when excessive thermal expansion of the roll occurs, compressive stress or shearing stress is applied to the surface of the work roll rotating in contact with the rolled plate, and heat cracks easily occur on the surface of the work roll under excessive thermal expansion.

However, when the rolling time and the rolling load are increased and the same rolling plate (material) is repeatedly rolled as described above even if cooling water is continuously sprayed to prevent thermal cracks and excessive thermal expansion of the work rolls as described above Heat cracks on the roll surface and, in severe cases, deformation of the work roll surface or excessive cracking and breakage occur, which degrades the rolling quality.

Therefore, in the related art, the cooling method of a rolling roll, particularly a work roll to which a hot rolled material is in contact, is improved, and when the thermal expansion of the rolling roll rapidly increases according to the conditions of the rolling material and the rolling schedule, There is a demand for rolling roll cooling apparatuses and methods which prevent thermal cracking of the rolling rolls and ultimately improve the cooling efficiency of the rolling rolls by implementing centralized cooling of the rolls.

In order to achieve the above-mentioned demand, the present invention is a rolling roll cooling method for cooling a rolling roll through a rolling roll cooling apparatus, wherein the rolling roll cooling apparatus includes a first cooling means provided on at least one side of a rolling roll, The first cooling means being provided on the upper side and the lower side from the first cooling means so as to allow centralized cooling of the rolling roll in correspondence with continuous rolling of the rolled material having a rolling gap or a similar width, Wherein the first cooling means comprises a cooling head provided in the mill housing in the longitudinal direction of the rolling roll and one or more spray nozzles provided in the cooling head to provide a further reduction in the width of the rolled material And the second cooling means is provided in the housing of the rolling mill so as to be able to move Wherein the cooling head of the second cooling means has a plurality of unit cells connected to each other along the longitudinal direction of the rolling roll, A main cooling step of injecting cooling water corresponding to the width of the material; And a concentrated cooling step of injecting cooling water to a portion corresponding to a widthwise center portion of the rolled material through the second cooling means.

According to the present invention as described above, it is possible to improve the cooling method of a rolling roll, particularly a work roll in direct contact with a hot rolled material (rolled plate), that is, (Rolling material having the same width) or the rolling schedule (the case where the rolling interval (time) is short), the thermal expansion of the rolling roll increases sharply.

Thus, the present invention enables centralized cooling of rolling rolls, that is, work rolls, to prevent thermal cracking of the rolling rolls even when excessive heat is transferred, and ultimately to improve the cooling efficiency of the rolling rolls.

That is, the present invention effectively reduces the thermal expansion of the work rolls, because it enables rapid centralized cooling of the work rolls even if thermal expansion of the work rolls can not be realized in the conventional simple injection system.

Ultimately, the present invention provides effects such as reducing heat cracking and excessive thermal expansion of the work roll during hot rolling, enabling the roll life of the work roll, improving the stability of rolling, and improving hot rolling productivity .

Fig. 1 is a process drawing showing a hot rolling step
Fig. 2 is a schematic view showing a cooling state of a work roll in a known hot rolling mill and a rolling roll of a backup roll during rolling
3 is a graph showing the temperature change of the work roll surface during hot rolling
4 is a schematic view showing a rolling roll cooling apparatus according to the present invention
5 and 6 are graphs showing the relationship between the centralized cooling range (X, Y) of the work roll in consideration of the width of the rolled material (plate) or the continuous rolling of the same width in the rolling roll cooling apparatus of the present invention, Y)
Fig. 7 is an exploded perspective view showing the rolling machine installed state of the rolling apparatus of the present invention
8 is an exploded perspective view showing a rolling machine cooling apparatus of the rolling apparatus of the present invention
9 is a front view showing the apparatus of the present invention
10 is a side view showing the apparatus of the present invention
11 is a configuration diagram showing another form of the cooling head in the apparatus of the present invention

Hereinafter, the present invention will be described in detail with reference to the drawings. In the following description of the present embodiment, the components related to the rolling mill, that is, the work roll, the rolling mill housing, and the like are described with reference numerals of 100 units, and the components related to the rolling roll cooling apparatus 1 according to the present invention are 10 units Will be described with reference numerals.

Also, the roll to be cooled through the apparatus of the present invention can be a rolling roll, that is, both a backup roll 120 and a backup roll supported work roll 130 as shown in FIG. 7, but is preferably in direct contact with a hot rolled material And the work roll 130 is a target.

Therefore, in the following description of the present embodiment, the rolling roll cooling apparatus will be described as the work roll cooling apparatus 1, and the rolling roll will be limited to the work roll 130 as well.

Of course, it is needless to say that the rolling roll cooling apparatus of the present invention is not necessarily limited to the work roll. The rolled material is described as rolled plate 140.

4 to 6 show the basic operation concept of the work roll cooling apparatus 1 according to the present invention, and Figs. 7 to 11 show the construction of the work roll cooling apparatus of the present invention in detail.

That is, as shown in Figs. 4 and 7 to 9, the work roll cooling apparatus 1 of the present invention roughly comprises at least one side of a work roll, preferably a first cooling means And a second cooling means (30) provided adjacent to the first cooling means (10) so as to be cooled in correspondence with the continuous rolling of the rolling material at a rolling gap or a similar width.

Therefore, the work roll rolling apparatus 1 of the present invention is provided with the second cooling means 30 different from the conventional one so that the rolling schedule or the rolling environment, that is, the rolling work roll 130, At least a partial cooling of the work roll is implemented in consideration of the rolling gap, the thickness and the width of the rolled plate, and the like, thereby preventing surface defect problems such as thermal cracking of the work roll, will be.

4 to 6, the second cooling means 30 is provided on the upper and lower sides starting from the first cooling means 10, and as described in detail later, And is capable of rapid cooling during continuous rolling of a rolled plate having a similar width (same width).

4 to 6, in the work roll cooling apparatus 1 of the present invention, the first cooling means 10 has at least the maximum width of the rolled plate 140 in the longitudinal direction of the work roll 130 And is provided as a main cooling means for adjusting the cooling water jetting range in correspondence with the width of the rolled plate 140.

At the same time, the second cooling means 30 cooperates with the first cooling means 10 in correspondence with the width of the rolled plate 140 so as to form one of the upper side and the lower side of the first cooling means 10, And is provided so as to be movable in the longitudinal direction of the work roll in order to realize centralized cooling of the work roll 130 on the lower side thereof.

The reason why the second cooling means 30 is provided as a movable type is that the second cooling means 30 is fixedly installed in the rolling mill housing 110 (Fig. 7), and when the cooling water injection control is performed, In the present invention, since the second cooling means 30 is provided in a movable form, the cooling water injection is implemented before the cooling water injection position is reached, so that during the concentrated cooling of the actual work roll 130, This is to realize rapid cooling while intensive cooling.

As shown in Figs. 4 to 6 and particularly in Fig. 7, in the apparatus of the present invention as described above, the first cooling means 10 is disposed between the both side housings 110 of the rolling mill, And one or more nozzles 14 provided in the first cooling head 12. The first cooling head 12 is provided with a first cooling head 12 extending to the first cooling head 12,

At this time, as shown in Figs. 4 and 7 and 8, the first cooling head 12 is provided in a structure including about six unit cells 12a-12f, and corresponds to the width of the rolled plate The cooling water can be independently supplied based on a pair of cells so as to inject the cooling water.

In one unit cell, two rows of cooling water nozzles 14 may be arranged to inject cooling water toward the work roll.

Next, as shown in Figs. 4 and 7 to 9, the second cooling means 30 is provided between the both side housings 110 of the rolling mill, like the first cooling means 10, As described in detail in FIG. 9, a cooling head 32 provided movably through the operation unit 50 and at least one nozzle 34 provided in the cooling head to implement the intensive cooling of the rapid or rolling roll Can be provided.

Unlike the first cooling water stage, the length of the second cooling means 30 is elongated in the longitudinal direction of the rolling roll, but may be smaller than that of the first cooling means. For example, four unit cells 32a- 32d may be provided in a structure in which cooling water is supplied to a pair of unit cells provided in a structure including a plurality of unit cells.

Next, Figs. 4 to 6 show the operating state of the work roll cooling apparatus 1 according to the present invention.

First, as shown in Fig. 4, the second cooling means 30 of the present invention is not used until the work roll 130 is replaced and the heat crown of the work roll is sufficiently generated, (Arrow direction) through the operation unit 50, which is described in detail in Fig. 9, and realizes cooling of the work roll through the main first cooling means 10. [

Next, FIGS. 5 and 6 show a state in which the second cooling means 30 is used in addition to the first cooling means 10 in the present invention. The second cooling means 30, for example, 1 central cooling of the work roll 130 is realized through the second cooling means 30 arranged above and below the cooling means 10 so that the cooling range X or Y As shown in Fig.

5, the centralized cooling of the work roll 130 is achieved through the second cooling means 30, but the cooling width X is minimized. In the case of FIG. 6, the second cooling means 30 To achieve the concentrated cooling of the work roll 1 but maximizes the cooling width Y thereof.

Of course, it is needless to say that the first cooling means 10 basically co-operates with cooling.

For example, as shown in Fig. 5, when the rolling plate 140 having the minimum width is continuously rolled, the thermal expansion at the central portion of the work roll 130 increases sharply. As shown in Fig. 5, (32a-32d) of the second cooling heads (32) of the upper and lower second cooling means (30) in combination But. The cooling water is injected only in a pair of unit cells on the left side.

Next, in FIG. 6, the concentrated cooling width Y is enlarged. For example, unlike FIG. 5, the width of the rolled plate increases, or the rolled plate of the same width or a high- In the case of continuously rolling the hot rolled plate, the concentrated cooling width Y is enlarged differently from that in Fig.

The adjustment of the cooling width of the second cooling means 30 to 'X' or 'Y' in FIGS. 5 and 6 can be achieved by changing the moving width of the second cooling means 30 once -9) of the second cooling head 32 while adjusting the cooling water injection of the unit cells 32a-32d for adjusting the cooling water width of the second cooling head 32. [

5 and 6 illustrate that a pair of unit cells of the second cooling head 32 are combined and a pair of unit cells of the first cooling head 12 are combined to inject cooling water. It is also possible to control the cooling water supply amount of the unit cells of the cooling water injector to adjust the cooling water injection width to the number of the cells to be injected.

However, in the case of adjusting by the cooling water supply of each unit cell, since the cooling water supply line (line) becomes too complex, a pair of unit cells are combined as one group, It may be desirable to adjust the width.

4 to 6, the number of unit cells of the first cooling head of the first cooling means is six and the number of unit cells of the second cooling head of the second cooling means 30 is four , The number of these unit cells can be appropriately adjusted.

4 to 10, the first and second cooling heads 120 (32) of the first and second cooling means 10 and 30 are formed into a box shape and the cooling water is sprayed toward the work roll from one side thereof Although two rows of spray nozzles 14 and 34 are shown, other types of cooling heads and nozzles are possible.

For example, as shown in Fig. 11, the cooling nozzles 14 and 34 may be provided in one row in the circular cooling heads 12 and 32, and the operation unit 50 may be connected to the cooling system It is also possible to do.

That is, the shape of the cooling head of the cooling means and the installation arrangement of the spray nozzles can be appropriately adjusted in consideration of the cooling water spraying conditions and the like.

As a result, the work roll cooling apparatus 1 of the present invention, which mainly describes changes in the spray width in FIGS. 4 to 6, includes a first cooling means 10 for spraying cooling water at the center corresponding to the width of the main rolling plate, (The cooling water is sprayed further from the second cooling means, which is smaller in length than the first cooling means for adjusting the cooling water jetting width (X, Y, etc.) Through the second cooling means 30, which realizes the optimum cooling of the work roll according to the rolling schedule or the width of the rolled plate. It is possible to achieve sufficient cooling even when rapid thermal expansion of the work roll is formed, in particular, to effectively suppress generation of heat cracks in the work roll, to provide excellent cooling water spray response (quickness), and to realize a stable cooling environment.

Next, in Figs. 7 to 9, the work roll cooling apparatus 1 according to the present invention is described in detail.

First, as shown in Figs. 7 and 8, the first cooling means 10 of the first cooling means 10, which is the central-side main cooling means, is provided with connecting hardware 12a such as a bracket on both sides of the cooling head 12 The cooling head can be assembled to the rolling mill housing 110 in a resolvable manner.

Alternatively, it is also possible that a support plate (not shown) is assembled in the housing and the first cooling head 12 is assembled to the spray direction of the spray nozzles 14 on one side of the support plate.

7 is an enlarged view of the work roll cooling apparatus 1 of the present invention rather than the housing 110 of the rolling mill 100 and the backup roll 120 and the work roll 130. Actually, Cooling devices based on the first and second cooling means 10, 30 of the present invention can be provided on both sides of the work roll 130, respectively.

Although it is schematically shown in the drawings, the present invention apparatus may be connected across the outer surface of the rolling mill housing 110 or may be disposed in the space between the rolling rolls inside the housing, but in the actual line, It is desirable to provide the second cooling means 30 at an optimum position in consideration of the movement (width) thereof.

As shown in FIG. 7, the cooling heads 12 and 32 of the first and second cooling units 10 and 30 of the present invention include unit cells 12a-12f, 32a-32d, Cooling water supply ports 16 and 36 are connected to the pair of unit cells, and cooling water supply hoses 18 and 38 are connected to the center side of the pair of unit cells.

At this time, the first cooling means 10 is fixed to the housing but is not limited to the cooling water supply hose of the supply port connected to the unit cells of the second cooling head 32 of the second cooling means 30 It is preferable that the cooling water supply hoses are connected to the supply port so as to compensate for the movement width of the second cooling head by providing a margin in length while being flexible in consideration of the movement width thereof.

Next, Figs. 8 to 10 show an operation unit 50 that enables the second cooling means 20 to be quickly moved in the longitudinal direction of the work roll 130. Fig.

That is, as shown in Figs. 8 to 10, The operation unit 50 provided in association with the second cooling water end in the apparatus of the present invention includes a rail member 52 provided between the housings 110 and to which the cooling head 32 is movably mounted, Or housing, and drive means associated with the cooling head.

Therefore, the second cooling head 32 can quickly move in the longitudinal direction of the work roll while advancing or retracting along with the operation of the driving means along the rail member 52.

In this way, the rail member 52 may actually have a structure corresponding to the shape of the second cooling head 32. For example, as shown in FIG. 10, in the case of a box-shaped cooling head, (Not shown) in which a guide 52b provided in the cooling head 32 is inserted may be provided at one side of the rail member 52, and in particular, the cooling head 32 may be provided with a guide groove And the rail member 52 to which the rail member 52 contacts can be attached and provided with liner 54 for reducing the wear and facilitating the movement.

Alternatively, in the case of the cylindrical cooling head 32 as shown in Fig. 11, the rail member 52 is bent in a pipe cutting structure, and a liner (see 54 in Fig. 10) .

10 and 11 are side views of the movable second cooling means 30 of the present invention. The driving means 60 and 70 will be described in detail below.

Next, as shown in Figs. 7 to 10, the driving means 50 (60) of the operating unit 50 enabling the movement of the second cooling means 30 can be provided in various forms, As shown in Figs. 7 to 9, the first driving means 60 and the second driving means 60 are shown on the upper and lower sides, respectively, with reference to the first cooling means.

Of course, it is preferable to select one of the first driving means 50 or the second driving means 60. For example, in the case of realizing the precise movement, Means 50 may be used.

7 to 9, in the apparatus of the present invention, the first driving means 60 is connected to the second cooling head 32, And one or more moving blocks 62 protruding from the movable member 52 through the movable member 52a and a ball screw 64 connected to the motor 66 mounted on the rail member 52, have.

One end of the ball screw 64 is assembled to the bearing block 64a provided on the other side of the rail member 52 and the other end is connected to the motor 66 mounted on one side of the rail member.

However, it is preferable that the length of the rail member 52 and the grooves 52a provided on the rear surface of the rail member are adjusted in consideration of the moving width of the second cooling head 32.

For example, as shown in FIG. 4, when the cooling heads of the second cooling means 30 do not perform centralized cooling and return to the home position, they are provided at a length that takes into account at least the length of the second cooling head 32 Needless to say.

8 and 9, when the motor 66 of the first driving means 60 is operated, the moving blocks 62 fastened to the ball screw 64, which is rotationally driven, move in the longitudinal direction of the work roll The fast and precise movement of the cooling head 32 of the movable second cooling means along the rail member 52 is controlled.

That is, as shown in FIGS. 5 and 6, it is possible to easily control the movement width of the second cooling head 32 selectively having the cooling water concentrated spray width as 'X' or 'Y'.

8 and 9, it is preferable that the rail member 52 is assembled to the rolling housing so as to be detachable by a bolting operation through a bracket or the like rather than being fixed to the housing by welding or the like.

For example, if the second cooling means 20 and the operation unit 50 are made of one set component, they can be directly attached to a desired position on the housing and used. Of course, it is natural to implement an electrical system.

Next, the second driving means 70 provided in the lower side of the first cooling means in Figs. 7 to 9 is a connecting block (not shown) provided in the second cooling head 32 and passing through the rail member 52 72 and a horizontal drive cylinder 74 connected to the connection block and provided on the rail member.

Of course, in the case of the horizontal drive cylinder 74, it is natural to adjust the stroke corresponding to the movement width thereof and mount the cylinder satisfying the stroke.

Therefore, when the horizontal driving cylinder 74 is moved forward or backward, the second cooling head 32 is quickly moved to the left or right in the longitudinal direction of the work roll.

On the other hand, since the moving block 62 and the connecting block 72 of the first or second driving means 60 and 70 are fastened through the ball screw and the rod 76 of the cylinder 74 is connected , So that the second cooling head 32 will not be detached from the rail member but will be able to move along the rail member stably.

Accordingly, the work roll cooling method of the present invention based on the work roll cooling apparatus 1 of the present invention described above can be summarized as follows. As shown in FIGS. 7 to 9, A main cooling step of spraying main cooling water on at least one side of the rolling mill work roll 130, preferably corresponding to the width of the rolled plate 140 at both sides of the rolling mill work roll 130 and at least one of upper and lower sides of the main cooling water injection position , And an intensive cooling step for implementing centralized cooling of the work roll by spraying additional cooling water so as to suppress thermal cracking due to thermal expansion of the work roll during continuous rolling of the rolling plate 140 having a rolling distance or a similar width .

At this time, the main cooling step and the central cooling step inject cooling water at least in correspondence with the width of the rolled material.

Alternatively, in the concentrated cooling step, the second cooling head 32 is moved on the premise that the cooling water is sprayed before the cooling water is first sprayed, so that the responsiveness of the cooling water spraying is improved even if the rolling interval of the work roll is narrowed. .

1 .... Rolling roll cooling device 10, 30 .... First cooling means
12,32 .... cooling head 14,34 .... coolant spray nozzle
16,36 .... Cooling water supply port of unit cell 18,38 .... Cooling water supply hose
50 .... operation unit 52 .... rail member
60, 70 .... drive means 62 .... movable block
64 .... ball screw 66 .... motor
72 .... connecting block 74 .... horizontal drive cylinder
110 .... rolling machine housing 130 .... rolling roll (work roll)
140 .... Rolled material (Rolled plate)

Claims (1)

A rolling roll cooling method in which a rolling roll is cooled through a rolling roll cooling apparatus,
The rolling roll cooling apparatus includes a first cooling means (10) provided at least on one side of a rolling roll, and a second cooling means (10) provided on at least one side of the rolling roll, (30) adjacent to said first cooling means (10), said second cooling means being provided above and below said first cooling means (10) and providing additional cooling of the rolling rolls,
The first cooling means 10 includes a cooling head 12 provided in the rolling mill housing 110 in the longitudinal direction of the rolling roll and one or more injection nozzles 14 provided in the cooling head to correspond to the width of the rolled material And the second cooling means 30 is provided with a cooling head 32 which is movably provided in the rolling mill housing 110 via an operation unit 50 and a cooling head 32 which is provided movably via the operation unit 50, The cooling head 32 of the second cooling means 30 is connected to a plurality of unit cells along the longitudinal direction of the rolling roll,
A main cooling step of injecting cooling water corresponding to the width of the rolled material through the first cooling means (10); And
And a concentrated cooling step of injecting cooling water to a portion corresponding to a widthwise central portion of the rolled material through the second cooling means (30).

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