ROLLER LEVELER AND METAL SHEET FLATTENING METHOD

Abstract

A roller leveler for flattening a metal sheet or plate having a cut-sheet form includes leveling rolls disposed in a staggered state on upper and lower sides of a pass line and configured to sandwich and flatten the metal sheet while pressing it therethrough, a hydraulic pressing cylinder for pressing the metal sheet via the leveling rolls, intermediate rolls set in contact with the respective leveling rolls from outside and larger in diameter than the leveling rolls, and a drive unit for rotating the intermediate rolls. The roller leveler causes the drive unit to rotate the intermediate rolls and transmits the driving force to the leveling rolls to pass the metal sheet while causing the pressing cylinder to press the metal sheet via the leveling rolls.

Description

TECHNICAL FIELD

The present invention relates to a roller leveler for flattening a metal sheet or plate having a cut-sheet form and a metal sheet flattening method.

BACKGROUND ART

In the process of manufacturing a metal sheet, such as a steel sheet, the metal sheet is subjected to rolling and cooling steps, in which the metal sheet undergoes deformation, such as warping and/or waving. Accordingly, in order to remedy the deformation, such as warping and/or waving, and thereby to flatten the metal sheet, a roller leveler, which includes a plurality of leveling rolls disposed on upper and lower sides in a staggered state, is used (for example, Patent Document 1).

The roller leveler is configured to pass a metal sheet to be flattened between the lower rolls and the upper rolls, while pushing the upper rolls toward the lower rolls or pushing the lower rolls toward the upper rolls, to repeatedly apply bending to the metal sheet, and thereby to planarize the warping and/or waving of the metal sheet. At this time, the pressing amount of the respective rolls of the roller leveler is suitably set to bend the metal sheet at a yield ratio preferably of 0.7 or more.

PRIOR ART DOCUMENT

Patent Document

Patent Document 1

Jpn. Pat. Appln. KOKAI Publication No. 2009-255148

SUMMARY OF INVENTION

When a conventional roller leveler is used to flatten a metal sheet having a cut-sheet form, the driving force for passing the metal sheet depends on the torque of the leveling rolls. In order to flatten a thin metal sheet made of a material with a larger yield stress, the diameter of the rolls needs to be small. This brings about a problem such that, if it is arranged to ensure the yield ratio necessary for the flattening, the torque of the leveling rolls becomes insufficient to pass the metal sheet.

This is because, in order to apply a sufficient pressing amount, drive shafts connected to drive the leveling rolls need to have a diameter smaller than that of the rolls. For this reason, when the leveling rolls have a small diameter to flatten a thin metal sheet, which is made of a material with a larger yield stress, their torque inevitably becomes small. In this case, the torque may be smaller than the value necessary for passing the metal sheet if it is arranged to ensure the yield ratio necessary for flattening the metal sheet.

In light of this problem, conventionally, when flattening is performed on a metal sheet having a small thickness and a large yield stress, it is necessary to restrictively set the pressing amount of the leveling rolls to a value that enables the sheet passing even by the torque of the leveling rolls. Consequently, there may be a case where the metal sheet is not sufficiently flattened.

The present invention has been made under the circumstances, and an object of the present invention is to provide a roller leveler and a metal sheet flattening method, which can sufficiently flatten a metal sheet having a small thickness and a large yield stress.

In order to solve the problem mentioned above, the present invention includes the following aspects.

According to a first aspect of the present invention, there is provided a roller leveler for flattening a metal sheet having a cut-sheet form, the roller leveler including: a plurality of leveling rolls disposed in a staggered state on upper and lower sides of a pass line of the metal sheet to be flattened and configured to rotate to sandwich and flatten the metal sheet while passing the metal sheet therethrough; a hydraulic pressing cylinder configured to press the metal sheet via the leveling rolls; a plurality of intermediate rolls disposed outside the plurality of leveling rolls on the upper and lower sides and set in contact with the respective leveling rolls from outside, the intermediate rolls having a diameter larger than that of the leveling rolls; and a drive unit configured to rotate the intermediate rolls, wherein the roller leveler is configured to cause the drive unit to drive the intermediate rolls for rotation and cause a driving force therefrom to be transmitted to the leveling rolls to pass the metal sheet while causing the pressing cylinder to press the metal sheet via the leveling rolls.

According to a second aspect of the present invention, there is provided a roller leveler including: a plurality of leveling rolls disposed in a staggered state on upper and lower sides of a pass line of a metal sheet to be flattened and configured to rotate to sandwich and flatten the metal sheet while passing the metal sheet therethrough; a plurality of intermediate rolls disposed outside the plurality of leveling rolls on the upper and lower sides and set in contact with the respective leveling rolls from outside, the intermediate rolls having a diameter larger than that of the leveling rolls; a pair of roll frames that support the leveling rolls and the intermediate rolls on the upper and lower sides, respectively; a pair of frames that support the pair of roll frames on the upper and lower sides, respectively; a hydraulic pressing cylinder configured to press one of the pair of frames to press the metal sheet via one of the roll frames, the intermediate rolls, and the leveling rolls; a drive unit configured to rotate the intermediate rolls; a plurality of hydraulic crowning cylinders arrayed in a width direction perpendicular to a pass direction of the metal sheet between one of the frames configured to be pressed by the pressing cylinder and a corresponding one of the roll frames; and a control system configured to control flattening of the metal sheet, wherein the control system is configured to perform control to cause the drive unit to drive the intermediate rolls for rotation and cause a driving force therefrom to be transmitted to the leveling rolls while causing the pressing cylinder to press the metal sheet via the leveling rolls, with the metal sheet being passed between the leveling rolls on the upper and lower sides, and wherein the control system is configured to obtain lateral deflection amounts of the pair of frames, to calculate necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for the deflection amounts, and to control tightening of the respective hydraulic crowning cylinders based on the necessary tightening amounts.

In the second aspect, it is preferable that the control system be configured to calculate necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for compressive deformation of the pressing cylinder, the hydraulic crowning cylinders, the pair of roll frames, the intermediate rolls, and the leveling rolls based on information on the compressive deformation, and to control tightening of the respective hydraulic crowning cylinders based on a total value of the necessary tightening amounts necessary for compensating for the compressive deformation and the necessary tightening amounts necessary for compensating for the deflection amounts of the pair of frames.

In the first and second aspects, it is preferable that the intermediate rolls have a diameter 1.2 to 2 times as large as a diameter of the leveling rolls, and the leveling rolls have a pitch, on each of the upper and lower sides, 1.2 to 2 times as large as the diameter of the leveling rolls. Further, it is preferable that the intermediate rolls be configured to be individually driven.

According to a third aspect of the present invention, there is provided a metal sheet flattening method of flattening a metal sheet having a cut-sheet form in a roller leveler, which includes a plurality of leveling rolls disposed in a staggered state on upper and lower sides of a pass line of the metal sheet to be flattened and configured to rotate to sandwich and flatten the metal sheet while passing the metal sheet therethrough, a hydraulic pressing cylinder configured to press the metal sheet via the leveling rolls, a plurality of intermediate rolls disposed outside the plurality of leveling rolls on the upper and lower sides and set in contact with the respective leveling rolls from outside, the intermediate rolls having a diameter larger than that of the leveling rolls, and a drive unit configured to rotate the intermediate rolls, the method including: inserting the metal sheet between the leveling rolls on the upper and lower sides; causing the pressing cylinder to press the metal sheet via the leveling rolls; and causing the drive unit to drive the intermediate rolls for rotation and causing a driving force therefrom to be transmitted to the leveling rolls to pass the metal sheet.

According to a fourth aspect of the present invention, there is provided a metal sheet flattening method of flattening a metal sheet having a cut-sheet form by use of a roller leveler, which includes a plurality of leveling rolls disposed in a staggered state on upper and lower sides of a pass line of the metal sheet to be flattened and configured to rotate to sandwich and flatten the metal sheet while passing the metal sheet therethrough, a plurality of intermediate rolls disposed outside the plurality of leveling rolls on the upper and lower sides and set in contact with the respective leveling rolls from outside, the intermediate rolls having a diameter larger than that of the leveling rolls, a pair of roll frames that support the leveling rolls and the intermediate rolls on the upper and lower sides, respectively, a pair of frames that support the pair of roll frames on the upper and lower sides, respectively, a hydraulic pressing cylinder configured to press one of the pair of frames to press the metal sheet via one of the roll frames, the intermediate rolls, and the leveling rolls, a drive unit configured to rotate the intermediate rolls, and a plurality of hydraulic crowning cylinders arrayed in a width direction perpendicular to a pass direction of the metal sheet between one of the frames configured to be pressed by the pressing cylinder and a corresponding one of the roll frames, the method including: inserting the metal sheet between the leveling rolls on the upper and lower sides; causing the pressing cylinder to press the metal sheet via the leveling rolls; and causing the drive unit to drive the intermediate rolls for rotation and causing a driving force therefrom to be transmitted to the leveling rolls to pass the metal sheet; and obtaining lateral deflection amounts of the pair of frames; calculating necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for the deflection amounts; and controlling tightening of the respective hydraulic crowning cylinders based on the necessary tightening amounts.

In the fourth aspect, it is preferable that the method include calculating necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for compressive deformation of the pressing cylinder, the hydraulic crowning cylinders, the pair of roll frames, the intermediate rolls, and the leveling rolls based on information on the compressive deformation; and controlling tightening of the respective hydraulic crowning cylinders based on a total value of the necessary tightening amounts necessary for compensating for the compressive deformation and the necessary tightening amounts necessary for compensating for the deflection amounts of the pair of frames.

In the third and fourth aspects, it is preferable that the intermediate rolls have a diameter 1.2 to 2 times as large as a diameter of the leveling rolls, and the leveling rolls have a pitch, on each of the upper and lower sides, 1.2 to 2 times as large as the diameter of the leveling rolls. Further, it is preferable that the intermediate rolls be configured to be individually driven.

In the first to fourth aspects, it is preferable that a penetration depth to the metal sheet be reduced until a leading end of the metal sheet passes through an area where the leveling rolls are disposed, and then is set at a value necessary for flattening the metal sheet after the leading end of the metal sheet passes through the area where the leveling rolls are disposed.

In the present invention, it is preferable that the metal sheet to be flattened be a steel sheet having a thickness of 2.0 to 25.4 mm and a yield stress of 400 to 1,800 MPa.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a roller leveler according to an embodiment of the present invention.

FIG. 2 is a front view showing the roller leveler according to the embodiment of the present invention.

FIG. 3 is a diagram for explaining the principle of the present invention.

FIG. 4 is a diagram, where the abscissa axis denotes the sheet thickness and the ordinate axis denotes the yield stress, showing a flattenable region, in which flattening can be performed at a yield ratio of 70% (0.7), respectively obtained in the case of the leveling rolls being used alone and in the case of the leveling rolls being used along with a drawing operation by pinch rolls.

EMBODIMENT FRO CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a side view showing a roller leveler according to an embodiment of the present invention. FIG. 2 is a front view showing the roller leveler. The roller leveler 100 according to this embodiment is designed to flatten a metal sheet having a cut-sheet form, and includes a housing 1, an upper frame 2 disposed inside the housing 1, and a lower frame 3 disposed to support the housing 1, as shown in the drawings. Hydraulic pressing cylinders (which may be referred to as “pushing cylinders”) 4 are disposed between the housing 1 and the upper frame 2, and an upper roll frame 5 is disposed below the upper frame 2 and is hung by an upper roll grip cylinder (not shown). A plurality of upper intermediate rolls 13 and upper leveling rolls 6 are disposed below the upper roll frame 5 and supported by the upper roll frame 5. The upper intermediate rolls 13 and the upper leveling rolls 6 are each formed of a long body extending in the width direction, and the upper intermediate rolls 13 are set in contact with the upper side of the upper leveling rolls 6. A plurality of upper backup rolls 7 are disposed between the respective upper intermediate rolls 1.3 and the upper roll frame 5 to back up the upper intermediate rolls 13. The upper backup rolls 7 are each formed of a short body and supported by the upper roll frame 5 along the axial direction of the upper intermediate rolls 13. Accordingly, the pressing cylinders 4 press down the upper roll frame 5, the upper backup rolls 7, the upper intermediate rolls 13, and the upper leveling rolls 6.

In this specification, the term “press down” is intended to include not only a case where the pressure is applied downward as shown in FIG. 1 but also a case where the pressure is applied upward as explained later in a modification. In other words, the term “press down” can be replaced with the term “press” in this specification.

On the side opposite to the upper leveling rolls 6 with respect to the pass line of the metal sheet P, a plurality of lower leveling rolls 8 are disposed and a plurality of lower intermediate rolls 14 are disposed below the lower leveling rolls 8. The lower leveling rolls 8 and the lower intermediate rolls 14 are supported by a lower roll frame 10 disposed therebelow. The lower leveling rolls 8 and the lower intermediate rolls 14 are each formed of a long body extending in the width direction, and the lower intermediate rolls 14 are set in contact with the lower side of the lower leveling rolls 8. A plurality of lower backup rolls 9, each being formed of a short body, are disposed along the axial direction of the lower intermediate rolls 14 between the respective lower intermediate rolls 14 and the lower roll frame 10 to back up the lower intermediate rolls 14 and are supported by the lower roll frame 10. The lower roll frame 10 is disposed on the lower frame 3. In place of the pressing cylinders 4 for pressing the upper leveling rolls 6, pressing cylinders for pressing the lower leveling rolls 8 may be used.

The upper intermediate rolls 13 and the lower intermediate rolls 14 have a diameter larger than the diameter of the upper leveling rolls 6 and the lower leveling rolls 8. The diameter of the upper intermediate rolls 13 and the lower intermediate rolls 14 is set preferably at 1.2 to 2.0 times, and more preferably at 1.4 to 2.0 times, as large as the diameter of the upper leveling rolls 6 and the lower leveling rolls 8. The pitch of the plurality of upper leveling rolls 6 and the plurality of lower leveling rolls E is set preferably at 1.2 to 2.0 times, and more preferably at 1.4 to 2.0 times, as large as the diameter of the upper leveling rolls 6 and the lower leveling rolls 8, as in the case of the diameter of the upper intermediate rolls 13 and the lower intermediate rolls 14. This pitch is equal to or larger than the conventional pitch, because the corresponding pitch according to the conventional roller levelers is set at 1.02 to 1.2 times the diameter of the leveling rolls. If the pitch of the leveling rolls is larger than 2.0 times the diameter of the leveling rolls, the sets of leveling rolls on the opposite sides bite into each other, thereby hindering the yield ratio from increasing.

The upper intermediate rolls 13 and the lower intermediate rolls 14 are respectively provided with drive units 15 (FIGS. 1 and 2 show only one unit for the sake of convenience) each including a rotary motor, so that the upper intermediate rolls 13 and the lower intermediate rolls 14 are rotated by the drive units 15. The driving force of the drive units 15 is transmitted to the upper leveling rolls 6 and the lower leveling rolls 8 to pass the metal sheet P between the upper leveling rolls 6 and the lower leveling rolls 8, while pressing the metal sheet P by the pressing cylinders 4 via the upper leveling rolls 6 to flatten the metal sheet P.

The upper frame 2 and the upper roll frame 5 are coupled with each other by a plurality of hydraulic crowning cylinders 12 disposed therebetween. As shown in FIG. 2, the respective crowning cylinders 12 are disposed at regular intervals to correspond to the leveling rolls 6 and 8 in the width direction perpendicular to the pass direction of the metal sheet P. As shown in FIG. 1, the hydraulic crowning cylinders 12 are arrayed in two rows. Although the crowning cylinders may be disposed in a row, the crowning cylinders disposed in two rows make it possible to more finely correct the local lateral deflection of the upper roll frame 5. The hydraulic crowning cylinders 12 are each equipped with a position detection sensor (not shown) built therein. The hydraulic crowning cylinders may be disposed between the lower roll frame 10 and the lower frame 3, or they may be disposed on both of the upper and lower sides.

As shown in FIG. 2, deflection detection sensors 21 are disposed at positions central in the horizontal direction above the upper frame 2 and configured to detect the lateral deflection of the upper frame 2. As shown in FIG. 1, the deflection detection sensors 21 are two sensors arranged along the pass line of the metal sheet P. The deflection detection sensors 21 continuously detect the distances to the lower side of the upper frame 2 to calculate the deflection amount of the upper frame 2 based on the distances. Further, deflection detection sensors 22 are disposed in internal space of the lower frame 3. The deflection detection sensors 22 are two sensors arranged, at positions central in the lateral direction, along the pass line of the metal sheet P. The deflection detection sensors 22 continuously detect the distances to the upper side of the lower frame 3 to calculate the deflection amount of the lower frame 3 based on the distances. The configuration described above may be modified such that only one of the upper frame 2 and the lower frame 3 is provided with deflection detection sensors and the deflection amount of the other frame is calculated using proportion.

Load cells (or hydraulic pressure converters) 23 are attached between the pressing cylinders 4 and the housing 1, and used to detect compressive deformation of the pressing cylinders 4, hydraulic crowning cylinders 12, upper roll frame 5, upper backup rolls 7, upper intermediate rolls 13, upper leveling rolls 6, lower leveling rolls 8, lower intermediate rolls 14, lower backup rolls 9, and lower roll frame 10.

The roller leveler 100 according to this embodiment is designed such that a control system 50 controls its respective components. The control system 50 includes a process controller having a CPU, a user interface connected to the process controller and having a keyboard and a display, and a storage section that stores recipes containing control programs (software) and process condition data recorded therein.

A required recipe is retrieved from the storage section and executed by the process controller in accordance with an instruction or the like input through the user interface. Consequently, the roller leveler 100 can perform a predetermined process (operational sequence) as described later under the control of the process controller. The recipes containing control programs and process condition data that are stored in a computer readable storage medium, such as a magnetic disk (flexible disk, hard disk, etc.), an optical disk (CD, DVD, etc.), a magneto-optical disk (MO, etc.), and/or a semiconductor memory, may be used.

Alternatively, the recipes may be available online, that is, may be transmitted from another apparatus through, e.g., a dedicated line, as needed.

In order to flatten the metal sheet P (i.e., to perform leveling), the control system 50 controls the penetration depth (pressing amount) of the leveling rolls 6 given by the pressing cylinders 4 and the driving of the intermediate rolls 13 and 14 made by the drive units 15. Further, the control system 50 receives information on the deflection of the upper frame 2 and the lower frame 3 sent thereto from the deflection detection sensors 21 and 22, or it receives, in addition to this information, information on the compressive deformation of the pressing cylinders 4, hydraulic crowning cylinders 12, upper roll frame 5, upper backup rolls 7, upper intermediate rolls 13, upper leveling rolls 6, lower leveling rolls 8, lower intermediate rolls 14, lower backup rolls 9, and lower roll frame 10 sent thereto. Then, the control system 50 uses its calculating function to calculate necessary tightening amounts of the respective hydraulic crowning cylinders 12 based on the pieces of information mentioned above, so that it controls the tightening by the respective hydraulic crowning cylinders 12 based on positional information obtained by the position detection sensors in the respective hydraulic crowning cylinders 12.

Next, an explanation will be given of an operation of the roller leveler 100 thus structured, in flattening a metal sheet P having a cut-sheet form.

When the leveling rolls 6 and 8 are used to reduce the internal stress of the metal sheet P by their driving force and flatten the metal sheet P, it is necessary to satisfy the following formula (1), where, in association with the metal sheet P, “t” (mm) is sheet thickness, E (N/mm²) is Young's modulus, δy (N/mm²) is yield stress, D (mm) is roll diameter, and n is yield ratio.

1−n=(δy.D)/(E.t)  (1)

In this formula, the yield ratio is required to be 0.7 or more to sufficiently reduce the internal stress. Accordingly, it is necessary to satisfy the following formula (2).

0.3 ≧(δy.D)/(E.t)  (2)

This formula can be transformed into the following formula (3).

D ≦0.3(E.t)/E.t)/δy  (3)

Accordingly, it is necessary that the smaller the sheet thickness “t” is or the larger the yield stress δy is, the smaller the diameter of the leveling rolls is set. However, the smaller the diameter of the leveling rolls is, the smaller the torque of the leveling rolls becomes.

Accordingly, when the leveling rolls are used to flatten a metal sheet having a small thickness and a large yield stress and are given a penetration depth (pressing amount) to obtain a yield ratio necessary for flattening the metal sheet, the material to be flattened, it may become difficult to pass the metal sheet because of an insufficient torque of the leveling rolls.

According to this embodiment made in light of this problem, the upper intermediate rolls 13 and the lower intermediate rolls 14 are respectively disposed above the upper leveling rolls 6 and below the lower leveling rolls 8 and they have a diameter larger than that of the leveling rolls 6 and 8. The upper intermediate rolls 13 and the lower intermediate rolls 14 are individually rotated by the drive mechanisms 15 to transmit the rotation to the upper leveling rolls 6 and the lower leveling rolls 8. The driving force thus transmitted is used to pass the metal sheet P between the upper leveling rolls 6 and the lower leveling rolls 8, while pressing the metal sheet P by the pressing cylinders 4, to flatten the metal sheet P. Consequently, the driving force for passing the metal sheet P increases and thereby makes it possible to pass the metal sheet while applying the pressing amount necessary for the flattening, even when the metal sheet has a small thickness and a large yield stress.

Next, this will be specifically explained.

FIG. 3 is a diagram for explaining the principles of an increase in the driving force that occurs when the intermediate rolls have a larger diameter. In the case where the leveling rolls are driven, the tangential force F₁ corresponding to the driving force for passing the metal sheet P is expressed by F₁=T/D, where D is the diameter of the leveling rolls and T is the torque of leveling rolls. On the other hand, in the case where the intermediate rolls having a larger diameter are driven and the driving force is transmitted to the leveling rolls, and the diameter of the intermediate rolls is twice as large as that of the leveling rolls or it is defined as 2D, the torque of the intermediate rolls is expressed by 8T because the torque is proportional to the cubic of the diameter. At this time, the tangential force F₂ corresponding to the force transmitted from the intermediate rolls to the leveling rolls is expressed by F₂=8T/2D, and thus F₂ is four times as large as F₁. The tangential force F₂ thus transmitted to the leveling rolls becomes the driving force for passing the metal sheet P. Accordingly, when the intermediate rolls doubled in diameter is driven and the driving force is transmitted to the leveling rolls, the sheet passing force for the metal sheet P increases fourfold. In the case where the diameter of the intermediate rolls is 1.2 times the diameter of the leveling rolls, this renders F₂=1.2³T/1.2D, which is 1.44 times as large as F₁, so that the sheet passing force for the metal sheet P increases 1.44 fold. In this way, the intermediate rolls having a larger diameter are disposed and driven to transmit the driving force to the leveling rolls, so that the driving force for passing the metal sheet P increases and thereby makes it possible to pass the metal sheet while applying the pressing amount necessary for the flattening, even when the metal sheet has a small thickness and a large yield stress.

In this case, as described above, the diameter of the upper intermediate rolls 13 and the lower intermediate rolls 14 is set preferably at 1.2 to 2.0 times, and more preferably at 1.4 to 2.0 times, as large as the diameter of the upper leveling rolls 6 and the lower leveling rolls 8. The pitch of the plurality of upper leveling rolls 6 and the plurality of lower leveling rolls 8 is set preferably at 1.2 to 2.0 times, and more preferably at 1.4 to 2.0 times, as large as the diameter of the upper leveling rolls 6 and the lower leveling rolls 8, as in the case of the diameter of the upper intermediate rolls 13 and the lower intermediate rolls 14. However, when the pitch of the leveling rolls is increased in this way, an increase in the penetration depth to the metal sheet P makes it difficult to pass the metal sheet P. In light of this problem, it is preferable to set the penetration depth smaller to pass the metal sheet P until the leading end of the metal sheet P passes through the area where the leveling rolls are disposed, that is, the leveling roll array area, and then to set the penetration depth at the required value to flatten the metal sheet P after the leading end of the metal sheet P passes through the leveling roll array area.

According to this embodiment, the flattening of the metal sheet P can be performed by a single passing of the metal sheet P through the leveling roll array area. However, as described above, there may be a case where the penetration depth is reduced to pass the metal sheet P until the leading end of the metal sheet P passes through the leveling roll array area. In such a case, in order to compensate for insufficient flattening at the portion including the leading end of the metal sheet P, it is preferable to pass the metal sheet P back and forth once or more through the leveling roll array area.

When the metal sheet used is a steel sheet, the technique according to this embodiment can be suitably used to process the steel sheet having a thickness of 2.0 to 25.4 mm and a yield stress of 400 to 1,800 MPa, which has been difficult to flatten.

FIG. 4 is a diagram, where the abscissa axis denotes the sheet thickness and the ordinate axis denotes the yield stress, showing the region (flattenable region), in which flattening can be performed at a yield ratio of 70% (0.7), respectively obtained in the case where the leveling rolls are driven and in the case where the intermediate rolls having a larger diameter are driven and the driving force is transmitted to the leveling rolls according to this embodiment. As shown in FIG. 4, use of the intermediate rolls having a larger diameter provides a remarkably expanded flattenable region, so that it is possible to flatten a material having a relatively small thickness of 12.7 mm or less and a large yield stress of 1,200 MPa or more, to obtain a metal sheet with high flatness. The relationship shown in FIG. 4 is obtained when the leveling rolls having a diameter of 135 mm are used to perform flattening.

As described above, by driving the intermediate rolls having a larger diameter, it is possible to flatten the metal sheet, the material to be flattened, with the required penetration depth (pressing amount) to attain high flatness. In this case, however, some of the components of the machine, such as the upper frame 2 and the lower frame 3, may be deflected in the width direction and, when this occurs, the penetration depth to the metal sheet varies in the width direction because of the deflection. Accordingly, in this embodiment, when it is desired to eliminate the influence of the deflection, detection values obtained by the deflection detection sensors 21 and/or 22 are used to derive the deflection amounts of the upper frame 2 and the lower frame 3. Then, the necessary tightening amounts of the respective hydraulic crowning cylinders 12 are calculated to compensate for the deflection amounts, and are used to perform a crowning correction on the upper leveling rolls 6. Consequently, it is possible to reduce the difference in the penetration depth in the width direction of the metal sheet P, the material to be flattened, which makes it possible to perform the flattening with higher flatness.

In addition to the necessary tightening amounts of the respective hydraulic crowning cylinders 12 necessary for compensating for the deflection amounts of the upper frame 2 and the lower frame 3, the necessary tightening amounts of the respective hydraulic crowning cylinders 12 for compensating for the compressive deformation may be calculated based on the information on compressive deformation obtained via the load cells (or hydraulic pressure converters) 23 attached between the pressing cylinders 4 and the housing 1, that is, the information on compressive deformation of the pressing cylinders 4, hydraulic crowning cylinders 12, upper roll frame 5, upper backup rolls 7, upper intermediate rolls 13, upper leveling rolls 6, lower leveling rolls 8, lower intermediate rolls 14, lower backup rolls 9, and lower roll frame 10, and the total value of the two sets of the necessary tightening amounts may be used to perform a crowning correction on the upper leveling rolls 6. This makes it possible to further reduce the difference in the penetration depth in the width direction of the metal sheet P, the material to be flattened, making it possible to perform the flattening with much higher flatness.

Japanese Patents No. 3443036 and No. 3726146 disclose crowning correction of this type in detail, the entire contents of which are incorporated by reference herein.

According to this embodiment of the present invention, intermediate rolls having a diameter larger than that of leveling rolls are disposed so as to be in contact with the leveling rolls from outside. A driving force is applied to the intermediate rolls to transmit the driving force to the leveling rolls, thereby passing a metal sheet between the leveling rolls. In this case, the driving force for passing the metal sheet can be increased. Consequently, even when the metal sheet has a small thickness and a large yield stress, it is possible to pass the metal sheet while applying a penetration depth necessary for the flattening, which improves the flatness of the metal sheet. Further, in addition to this, by performing the crowning correction in the width direction, it is possible to further improve the flatness of the metal sheet.

The present invention is not limited to the embodiment described above, and it may be modified in various manners. For example, in the embodiment described above, the machine has a structure designed to press (press downward) the upper rolls of the leveling rolls toward the lower rolls, but it may be modified to press (press upward) the lower rolls toward the upper rolls. Further, the present invention should be construed to encompass arrangements obtained by omitting some of the components of the embodiment described above, as long as they do not depart from the scope of the present invention.

Claims

1. A roller leveler for flattening a metal sheet having a cut-sheet form, the roller leveler comprising:

a plurality of leveling rolls disposed in a staggered state on upper and lower sides of a pass line of the metal sheet to be flattened and configured to rotate to sandwich and flatten the metal sheet while passing the metal sheet therethrough;

a hydraulic pressing cylinder configured to press the metal sheet via the leveling rolls;

a plurality of intermediate rolls disposed outside the plurality of leveling rolls on the upper and lower sides and set in contact with the respective leveling rolls from outside, the intermediate rolls having a diameter larger than that of the leveling rolls; and

a drive unit configured to rotate the intermediate rolls,

wherein the roller leveler is configured to cause the drive unit to drive the intermediate rolls for rotation and cause a driving force therefrom to be transmitted to the leveling rolls to pass the metal sheet while causing the pressing cylinder to press the metal sheet via the leveling rolls.

2. The roller leveler according to claim 1, further comprising:

a pair of roll frames that support the leveling rolls and the intermediate rolls on the upper and lower sides, respectively, wherein one of the pair of frames is configured to be pressed by the pressing cylinder from a side opposite to the leveling rolls;

a plurality of hydraulic crowning cylinders arrayed in a width direction perpendicular to a pass direction of the metal sheet between one of the frames configured to be pressed by the pressing cylinder and a corresponding one of the roll frames; and

a control system configured to control flattening of the metal sheet,

wherein the control system is configured to perform control to cause the drive unit to drive the intermediate rolls for rotation and cause a driving force therefrom to be transmitted to the leveling rolls while causing the pressing cylinder to press the metal sheet via the leveling rolls, with the metal sheet being passed between the leveling rolls on the upper and lower sides, and

wherein the control system is configured to obtain lateral deflection amounts of the pair of frames, to calculate necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for the deflection amounts, and to control tightening of the respective hydraulic crowning cylinders based on the necessary tightening amounts.

3. The roller leveler according to claim 2, wherein the control system is configured to calculate necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for compressive deformation of the pressing cylinder, the hydraulic crowning cylinders, the pair of roll frames, the intermediate rolls, and the leveling rolls based on information on the compressive deformation, and to control tightening of the respective hydraulic crowning cylinders based on a total value of the necessary tightening amounts necessary for compensating for the compressive deformation and the necessary tightening amounts necessary for compensating for the deflection amounts of the pair of frames.

4. The roller leveler according to claim 1, wherein the intermediate rolls have a diameter 1.2 to 2 times as large as a diameter of the leveling rolls, and the leveling rolls have a pitch, on each of the upper and lower sides, 1.2 to 2 times as large as the diameter of the leveling rolls.

5. The roller leveler according to claim 1, wherein the intermediate rolls are configured to be individually driven.

6. The roller leveler according to claim 1, wherein a pressing amount to the metal sheet is reduced until a leading end of the metal sheet passes through an area where the leveling rolls are disposed, and then is set at a value necessary for flattening the metal sheet after the leading end of the metal sheet passes through the area where the leveling rolls are disposed.

7. The roller leveler according to claim 1, wherein the metal sheet to be flattened is a steel sheet having a thickness of 2.0 to 25.4 mm and a yield stress of 400 to 1,800 MPa.

8. A metal sheet flattening method of flattening a metal sheet having a cut-sheet form in a roller leveler, which includes

a plurality of leveling rolls disposed in a staggered state on upper and lower sides of a

pass line of the metal sheet to be flattened and configured to rotate to sandwich and flatten the metal sheet while passing the metal sheet therethrough,

a hydraulic pressing cylinder configured to press the metal sheet via the leveling rolls,

a plurality of intermediate rolls disposed outside the plurality of leveling rolls on the upper and lower sides and set in contact with the respective leveling rolls from outside, the intermediate rolls having a diameter larger than that of the leveling rolls, and

a drive unit configured to rotate the intermediate rolls,

the method comprising: inserting the metal sheet between the leveling rolls on the upper and lower sides;

causing the pressing cylinder to press the metal sheet via the leveling rolls; and causing the drive unit to drive the intermediate rolls for rotation and causing a driving force therefrom to be transmitted to the leveling rolls to pass the metal sheet.

9. The metal sheet flattening method which according to claim 8, wherein the roller leveler further includes

a pair of roll frames that support the leveling rolls and the intermediate rolls on the upper and lower sides, respectively,

a pair of frames that support the pair of roll frames on the upper and lower sides, respectively, wherein one of the pair of frames is configured to be pressed by the pressing cylinder from a side opposite to the leveling rolls, metal sheet via one of the roll frames, the intermediate rolls, and the leveling rolls,

a plurality of hydraulic crowning cylinders arrayed in a width direction perpendicular to a pass direction of the metal sheet between one of the frames configured to be pressed by the pressing cylinder and a corresponding one of the roll frames,

the method further comprising: obtaining lateral deflection amounts of the pair of frames; calculating necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for the deflection amounts; and controlling tightening of the respective hydraulic crowning cylinders based on the necessary tightening amounts.

10. The metal sheet flattening method according to claim 9, wherein the method comprises calculating necessary tightening amounts of the respective hydraulic crowning cylinders necessary for compensating for compressive deformation of the pressing cylinder, the hydraulic crowning cylinders, the pair of roll frames, the intermediate rolls, and the leveling rolls based on information on the compressive deformation; and controlling tightening of the respective hydraulic crowning cylinders based on a total value of the necessary tightening amounts necessary for compensating for the compressive deformation and the necessary tightening amounts necessary for compensating for the deflection amounts of the pair of frames.

11. The metal sheet flattening method according to claim 8, wherein the intermediate rolls have a diameter 1.2 to 2 times as large as a diameter of the leveling rolls, and the leveling rolls have a pitch, on each of the upper and lower sides, 1.2 to 2 times as large as the diameter of the leveling rolls.

12. The metal sheet flattening method according to claim 8, wherein the intermediate rolls are configured to be individually driven.

13. The metal sheet flattening method according to claim 8, wherein a pressing amount to the metal sheet is reduced until a leading end of the metal sheet passes through an area where the leveling rolls are disposed, and then is set at a value necessary for flattening the metal sheet after the leading end of the metal sheet passes through the area where the leveling rolls are disposed.

14. The metal sheet flattening method according to claim 8, wherein the metal sheet to be flattened is a steel sheet having a thickness of 2.0 to 25.4 mm and a yield stress of 400 to 1,800 MPa.

15. The roller leveler according to claim 1, further comprising a plurality of backup rolls that back up the plurality of intermediate rolls on the upper and lower sides.

16. The metal sheet flattening method according to claim 8, wherein the roller leveler further includes a plurality of backup rolls that back up the plurality of intermediate rolls on the upper and lower sides.