Rolling machine and rolling method

Abstract

To provide a condition monitoring technique of extrusion amount by a chock restraint device which is used under inferior environment where position detection is difficult.SOLUTION: A rolling mill comprises: a pair of upper and lower work rolls which are vertically arranged sandwiching a rolled material; a pair of upper and lower auxiliary rolls which respectively and directly contact with the work rolls, or a pair of upper and lower auxiliary rolls which respectively contact through a pair of upper and lower intermediate rolls with the work rolls; a pair of roll chocks which rotatably and respectively support both ends of the work rolls, the intermediate rolls, and the auxiliary rolls; a pair of housings in which the roll chocks are installed directly or through a window configuration appliance by setting a space therebetween; a chock restraint device which presses the roll chock to an inlet side or an outlet side in a sheet passing direction of the rolled material; and monitoring means which monitors extrusion amount by the chock restraint device.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for monitoring the output of a device for restraining roll chocks during rolling, and to a rolling mill and a rolling method using the technique. [Background technology]

[0002] A rolling mill is used when rolling a material to be rolled, such as a steel plate. For example, as shown in Fig. 5, the rolling mill has a pair of upper and lower work rolls 6a (WR) that roll the material to be rolled, and a pair of upper and lower auxiliary rolls 6c that support the work rolls 6a. Furthermore, if necessary, a pair of upper and lower intermediate rolls 6b (IMR) are provided between the work rolls 6a and the auxiliary rolls 6c. The auxiliary rolls 6c are also called backup rolls (BUR).

[0003] In the equipment layout shown in FIG. 5, the various rolls 6a, 6b, and 6c of the rolling mill are attached to roll chocks 7, which include bearings that rotatably support both ends of the axial direction of each roll. The roll chocks 7 are installed in a pair of housings 8 arranged on the operation side (op side) and the drive side (dr side). In this case, a clearance is provided between the roll chocks 7 and a window 9 of the housing 8 to facilitate roll replacement work. Normally, the work rolls 6a and the intermediate rolls 6b have their roll centers shifted in the direction of the pass line PL, so that their own weights and rolling loads act on them and they are pressed against the inner surface of one of the housings 8, that is, the window 9. This is designed to stabilize the roll chocks even if a clearance (gap) exists.

[0004] However, if rolling is performed with the above clearance left as it is, the work roll 6a will be subjected to acceleration and deceleration forces in the pass line direction when the rolled material is bitten or removed, which will generate inertial forces in the roll body and cause the roll chock 7 to vibrate in the gap direction. The impact caused by the vibration of the roll chock 7 can be several tens of tf (several hundred kN), depending on the rolling conditions. This not only accelerates the rate of equipment deterioration, but also causes squeezing phenomena such as meandering and folding of the plate due to fluctuations in the roll gap, which can damage the rolls. If such an occurrence occurs, unscheduled roll changes will be required, which may reduce the equipment operating rate.

[0005] To solve the above problems, a chock restraining device as described in Patent Document 1 was introduced. This chock restraining device is placed on the opposite side to the offset direction of the roll changing device, which is a window component equipment. During rolling, the roll chocks are pressed against the roll changing device by a hydraulic cylinder to restrain them and suppress the vibration of the roll chocks. The hydraulic cylinder can be pressed and released at any timing, so it can be controlled to release the hydraulic cylinder when the rolls shift during roll changing or rolling, and to restrain the roll chocks during rolling.

[0006] However, if the hydraulic cylinder breaks down in the rolling mill, there is a high risk of equipment damage. For example, if the cylinder piston breaks down in a state where it protrudes into the clearance due to an oil leak or damage inside the hydraulic cylinder, it will interfere with the operation of the roll chocks caused by roll reassembly or roll shifting, causing damage to the equipment. Therefore, understanding the pressing state of the hydraulic cylinder, that is, the extrusion rate, is one of the very important items for condition monitoring.

[0007] Methods for monitoring the condition of such hydraulic cylinders include position detection using an encoder as described in Patent Document 2, and measuring the amount of displacement of a bellows diaphragm as described in Patent Document 3. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-008311 A [Patent Document 2] JP 2013-147291 A [Patent Document 3] Japanese Patent Application Publication No. 04-327316 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the above-mentioned conventional techniques have the following problems. That is, the hydraulic cylinder described in Patent Document 1 is completely buried in the window-constituting equipment, and during rolling when the rolls are inserted, it only strokes within a gap of about a few millimeters. In addition, since the view is physically blocked by the rolls during rolling, it is difficult to monitor the actual product using a fixed-point camera. In addition, the area around the rolling mill is narrow and crowded with hydraulically driven equipment. In addition, it is a poor environment that combines a hot environment where the rolled material is at a high temperature of 500°C or more, a dusty environment where the scale of the rolled material scatters, and a humid environment where cooling water for the rolls is constantly sprayed. Therefore, it is also difficult to install sensors such as an absocorder, a laser, or a vortex type.

[0010] Furthermore, the cylinder displacement measurement methods described in Patent Documents 2 and 3 make it possible to measure the internal flow rate due to minute stroke fluctuations of the cylinder, and are considered to be effective for the hydraulic cylinder with a small stroke amount described in Patent Document 1. However, both methods originally measure the stroke amount of the cylinder piston body with a displacement meter such as an encoder, which makes it difficult to apply them to hydraulic cylinders where the displacement cannot be physically measured.

[0011] The present invention has been made in consideration of the above circumstances, and has an object to provide a state monitoring technology for a chock restraint device used in a poor environment where position detection is difficult, and to provide a rolling mill and a rolling method using the technology. [Means for solving the problem]

[0012] The inventors discovered that by installing a flow meter on the hydraulic oil circuit of the hydraulic cylinder, rather than immediately next to the rolling mill, and measuring and comparing the amount of oil moving through the forward and return pipes, it is possible to remotely monitor the condition of the hydraulic cylinder without physically measuring the hydraulic cylinder itself, and completed the invention.

[0013] The rolling mill of the present invention which advantageously solves the above-mentioned problems comprises a pair of upper and lower work rolls arranged above and below with a material to be rolled therebetween, a pair of upper and lower auxiliary rolls which directly contact the work rolls, respectively, or a pair of upper and lower auxiliary rolls which contact the work rolls via a pair of upper and lower intermediate rolls which contact the work rolls, respectively, a pair of roll chocks which rotatably support both ends of the work rolls, the intermediate rolls and the auxiliary rolls, respectively, and a pair of housings to which the roll chocks are attached with a gap provided therebetween, either directly or via a window-forming facility, The present invention is characterized by comprising a chock restraining device which presses the roll chocks towards the entry side or exit side in the sheet passing direction of the rolled material, and a means for monitoring the extrusion amount of the chock restraining device.

[0014] In addition, the rolling mill according to the present invention has the following features: (a) the chock restraint device is a hydraulic cylinder type device installed inside the housing or the window component equipment, and the displacement is measured by the piston travel distance by integrating the flow rate of hydraulic oil; (b) the hydraulic oil is supplied to or recovered from the hydraulic cylinder device via a hydraulic circuit provided inside the housing or the window component equipment, and a sensor is provided along the hydraulic oil supply / recovery path to monitor the volumetric flow rate of the hydraulic oil; This is thought to be a more preferable solution.

[0015] The rolling method of the present invention, which advantageously solves the above-mentioned problems, is characterized in that it uses any one of the rolling mills described above, and at any time during rolling, presses the roll chocks toward the entry side or exit side in the sheet passing direction of the rolled material, and compares the measured extrusion rate with a predetermined value to determine an equipment abnormality.

[0016] In addition, in the rolling method according to the present invention, when the equipment abnormality judged to be an increase in the gap is detected, it is considered that a more preferable solution is to output an alarm and adjust the gap. Effect of the Invention

[0017] According to the rolling mill and rolling method of the present invention, the state of the chock restraining device is constantly monitored, thereby preventing equipment troubles. In particular, by monitoring the flow rate of hydraulic oil in the hydraulic cylinder, leak troubles and increases in the gap between the roll chock and the window can be monitored, and these can be used as guidelines for equipment maintenance. As a result, the equipment operating rate is expected to improve, which is industrially useful. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing features of a rolling mill according to an embodiment of the present invention. [Diagram 2] 5A and 5B are schematic diagrams showing the stroke state of the hydraulic cylinder according to the embodiment, in which (a) is an example of movement in a direction to restrain the roll chock, and (b) is an example of movement in a direction to release the roll chock. [Diagram 3] FIG. 1(a) is a schematic diagram showing the relationship between the amount of hydraulic oil supplied and the amount of extrusion of the hydraulic cylinder in the above embodiment, FIG. 1(b) shows the state in which the roll chocks are pressed and restrained, and FIG. 1(c) shows the state in which the cylinder has been pushed out to its maximum stroke without pressing the roll chocks. [Figure 4] 1A and 1B are schematic diagrams showing an example of a method for detecting wear of roll chocks and housing peripheral equipment using a hydraulic cylinder in the above embodiment, in which (a) shows a healthy state and (b) shows a state in which wear has progressed. [Diagram 5] 1A is a schematic diagram showing the equipment around the housing of a rolling mill, in which (a) shows the structure of the rolling mill, (b) shows window management, and (c) is an enlarged view of part A in (a) and shows a schematic diagram showing how to adjust the gap amount. [Figure 6] 4 is a graph showing the change over time in the amount of hydraulic oil transferred to a hydraulic cylinder for each passing of a plate using the rolling mill according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the present invention will be described in detail. The following embodiments are merely examples of devices and methods for embodying the technical ideas of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical ideas of the present invention can be modified in various ways within the technical scope described in the claims.

[0020] Fig. 5(a) is a cross-sectional view showing the structure of a housing on the operation side (op side) of a six-high rolling mill according to one embodiment of the present invention. This rolling mill is equipped with a pair of upper and lower work rolls 6a, 6a that roll the material to be rolled in the pass line PL direction. It is equipped with intermediate rolls 6b, 6b that contact the work rolls 6a, 6a, respectively. It is equipped with auxiliary rolls 6c, 6c that contact the intermediate rolls 6b, 6b, respectively. A housing 8 is arranged on the operation side (op side) at one end in the axial direction of these rolls. Similarly, a housing 8 is arranged on the drive side (dr side) at the other end.

[0021] In this embodiment, both axial ends of each roll are rotatably supported by roll chocks 7. Fig. 5(b) shows the concept of managing the interval in the pass line PL direction of windows 9, which are the inner surface of a housing 8, i.e., the window interval WL. A predetermined clearance is provided between the roll chocks 7 supporting each roll and the window 9. A vertically movable block member can be provided in the clearance to eliminate the gap in the pass line direction and regulate the movement in the pass line direction.

[0022] In the example of FIG. 5, a roll changing rail 5a for roll changing is provided as a window component 5 between the roll chock 7 of the intermediate roll 6b in the lower half of the rolling mill and the window 9. A predetermined gap is provided between the changing rail 5a and the roll chock 7. This gap is provided to facilitate the roll changing work. Specifically, when changing the rolls, the work rolls 6a, 6a are first pulled out, and then the changing rail 5a is raised by a cylinder or the like while supporting the upper intermediate roll 6b and the auxiliary roll 6c with a spacer or the like. As a result, a portion protruding in the pass line PL direction below the roll chock 7 for the lower intermediate roll 6b and a portion protruding in the conveying direction below the changing rail 5a are caught. Then, the lower intermediate roll 6b is pulled out upward. Next, the lower intermediate roll 6b pulled out upward is pulled out in the width direction of the passing plate material (toward the viewer of the drawing). In this way, when removing the lower intermediate roll 6b, it is necessary to pull up the reassembly rail 5a and then pull out the lower intermediate roll 6b in the width direction. To make these movements, it is necessary to provide a gap between the reassembly rail 5a and the roll chock 7 for the lower intermediate roll 6b.

[0023] In this embodiment, as shown in FIG. 1, a chock restraining device 1 is provided to eliminate the gap between the window forming equipment 5 and the roll chock 7. In the example of FIG. 1, the chock restraining device 1 is a hydraulic cylinder, and is embedded in the window forming equipment 5 on the exit side in the pass line direction. The roll chock 7 is pressed toward the window forming equipment 5 on the entry side of the rolled material in the pass line PL direction. This fixes the position of the roll chock 7 in the pass line PL direction, and prevents the roll chock 7 and the roll 6 from wobbling during the threading. The chock restraining device 1 may be embedded in the window forming equipment 5 on the entry side in the pass line PL direction, and presses the roll chock 7 against the exit side to restrain it.

[0024] In this embodiment, as shown in FIG. 2, a hydraulic cylinder 1 in which a piston reciprocates has a cylinder head side oil chamber 1a and a cylinder rod side oil chamber 1b whose volume varies according to the stroke. A head side hydraulic pipe 2a and a rod side hydraulic pipe 2b are provided to each of the oil chambers 1a and 1b, which are connected via a hydraulic oil path in a window configuration facility 5. The hydraulic oil is supplied from a hydraulic valve stand 4 to each of the oil chambers 1a and 1b via the hydraulic pipes 2a and 2b. A head side flow meter 3a and a rod side flow meter 3b are provided on each of the hydraulic pipes 2a and 2b. This flow meter makes it possible to detect the amount of hydraulic oil required for the cylinder stroke on the head side and the rod side, respectively. Therefore, even if there is no sensor in the immediate vicinity of the cylinder, it is possible to detect the cylinder stroke from the amount of oil supplied and the amount of oil discharged. As a flow meter, a laser Doppler type, an ultrasonic type, or the like can be used. The ultrasonic type is preferable because it does not require any selection of piping material. If the piping is transparent, a laser Doppler type flow meter can be applied without contact and without piping work.

[0025] Figure 2(a) shows the state in which hydraulic oil is supplied to the cylinder head side oil chamber 1a through the hydraulic piping 2a and the piston is stroking in the protruding direction, that is, in the direction that restrains the roll chock 7. This is defined as state 1. When the roll chock 7 comes into contact with the window component 5 and the restraint is completed, the stroke stops and the amount of hydraulic oil supplied to the cylinder head side oil chamber 1a also becomes zero. On the other hand, the hydraulic oil remaining in the cylinder rod side oil chamber 1b is discharged to the hydraulic valve stand 4 through the hydraulic piping 2b as the piston starts to stroke. At the same time as the stroke stops, the amount of discharge from the cylinder rod side oil chamber 1b also becomes zero. Figure 2(b) shows the state in which the piston is stroking in the retracting direction, that is, in the opening direction of the roll chock 7. This is defined as state 2. While hydraulic oil is supplied to the cylinder rod side oil chamber 1b, hydraulic oil in the cylinder head side oil chamber 1a is discharged. The start and stop timings of the stroke coincide with the start and stop timings of the stroke. Therefore, by measuring the amount of hydraulic oil passing through the hydraulic piping 2a during the stroke of the hydraulic cylinder 1 with the head side flow meter 3a, or by measuring the amount of hydraulic oil passing through the hydraulic piping 2b with the rod side flow meter 3b, it is possible to indirectly measure the stroke amount (displacement amount) of the cylinder.

[0026] At this time, the flow meters 3a and 3b measure the volumetric flow rate, so it is necessary to convert this to the amount of hydraulic oil that has moved (volume). As mentioned above, the movement of hydraulic oil due to the stroke of the hydraulic cylinder 1 is limited to the period from the start of the stroke to its completion. Therefore, if the time from the start of the stroke to its completion is t and the flow rate per unit time is Qx, the total amount of hydraulic oil that has moved, that is, the oil volume V, is given by the integral of Equation (1) in the following Equation 1.

[0027] TIFF0007633607000001.tif17152

[0028] As shown in Figure 3(a), for the oil volume V obtained here, let the head side oil volume be Va and the rod side oil volume be Vb. If the head diameter is Da, the rod diameter is Db, and the stroke volume is L1, then the equations (2) and (3) in the following equations 2 and 3 hold. By measuring the oil volumes Va and Vb, it is possible to calculate the cylinder stroke Lx from the head side using equation (2) and from the rod side using equation (3). Let the displacement of the hydraulic cylinder acting as a chock restraint device be the cylinder stroke Lx.

[0029]

number

number

[0030] As shown in Figure 3(c), the maximum stroke amount Lmax of the cylinder is a known value. If the oil volumes at the maximum stroke are VA and VB, respectively, then an arbitrary stroke amount Lx can be calculated from the following formula (4). By converting Lx into a numerical value and outputting it, for example, to the screen of an operating terminal operated by the rolling machine operator, it becomes possible to constantly monitor the stroke of the hydraulic cylinder 1.

[0031]

number

[0032] FIG. 3(b) shows a state in which the hydraulic cylinder 1 as a chock restraining device restrains the roll chock 7 and presses it against the facing window configuration equipment 5. Here, the stroke of the hydraulic cylinder and the mill window gap x match. The maximum cylinder stroke Lmax is greater than the mill window gap x. Therefore, if the amount of oil when the roll chock 7 is normally restrained is Vxa on the head side and Vxb on the rod side, then VA>Vxa and VB>Vxb. Note that the chock restraining device 1 may be an electric actuator instead of the hydraulic cylinder. In that case, it is preferable to measure the rotation speed and rotation angle using a pulse generator or the like to grasp the extrusion amount.

[0033] Next, a rolling method as another embodiment of the present invention will be described. In this embodiment, a method for detecting an abnormality in the chock restraining device using the state monitoring means of the chock restraining device 1 is included. That is, a method for pressing the roll chock 7 toward the inlet or outlet of the sheet passing direction (pass line PL) of the rolled material at any time during rolling, and for judging an equipment abnormality by comparing the measured extrusion rate with a predetermined value is also included. For example, during rolling, the chock restraining device 1 presses the roll chock 7 against the roll changing device 5a to restrain it and suppress the vibration of the roll chock 7. On the other hand, when the roll 6 shifts during roll changing or rolling, the roll chock 7 is released. It is assumed that the chock restraining device 1 is composed of the above hydraulic cylinder. On the premise that the hydraulic oil does not leak on the piping route, when the cylinder operates, Va / VA=Vb / VB from the above formula (4). It is necessary to judge an operation abnormality depending on the absolute amounts of Va and Vb. Therefore, the following methods can be selected as a method for managing the absolute amount of oil.

[0034] (1) Anomaly detection using thresholds When the cylinder operates normally, the oil volumes Va and Vb on the cylinder side and the rod side are equal to Vxa and Vxb respectively. When the rod moves in the protruding direction in State 1, if the cylinder stops due to some reason during the stroke without contacting the roll chuck 7 and becomes poorly constrained, then Va < Vxa and Vb < Vxb. Therefore, the judgment oil volumes Vfa (head side) and Vfb (rod side) during abnormal constraint are set as threshold values. If Va ≥ Vfa and Vb ≥ Vfb, it is judged as normal, and if Va < Vfa and Vb < Vfb, it is judged as abnormal. The same applies to State 2 when the rod moves in the retracting direction. When the stroke stops due to some reason during the retraction of the rod from the normally constrained state and does not return to the stroke retraction limit and stops halfway, then Va < Vxa and Vb < Vxb. Therefore, if Va ≥ Vfa and Vb ≥ Vfb, it is normal, and if Va < Vfa and Vb < Vfb, it is judged as abnormal. Here, it is preferable to set Vfa and Vfb to capture obvious abnormal values in consideration of the adjustment accuracy of each window component facility.

[0035] (2) Abnormality detection based on feedback values This is a method of detecting abnormalities based on the absolute oil volume used in the cylinder operation. Let the oil volumes on the cylinder side and the rod side that moved in State 1 be Va1 and Vb1 respectively, and let the oil volumes on the cylinder side and the rod side that moved in State 2 be Va2 and Vb2 respectively. Compare them, and if Va1 = Va2 and Vb1 = Vb2, it is judged as normal, and if Va1 ≠ Va2 and Vb1 ≠ Vb2, it is judged as abnormal. For each cylinder operation, Va1 and Vb1 are used as feedback values and compared with the oil volumes Va2 and Vb2 when the roll chuck 7 is released.

[0036] The above method (1) is a management method using absolute values, while the above method (2) is a management method using relative values. Therefore, it is preferable to use both methods to monitor for abnormalities. An abnormality here refers to the hydraulic cylinder not coming into contact with the roll chock 7 when stroking, or the operation stopping even though the stroke has not reached its retract limit. Possible causes for this include a blockage in the hydraulic piping path that cuts off the hydraulic oil supply, or physical interference due to damage inside the cylinder. In such cases, it is necessary to remove the blockage in the hydraulic path or replace the hydraulic cylinder 1.

[0037] Furthermore, according to this embodiment, the hydraulic cylinder 1 directly restrains the window configuration equipment 5 and the roll chock 7, so fluctuations in the mill window gap x can be detected from changes in the cylinder stroke. The wear of the window configuration equipment 5 and the roll chock 7 is the rate-limiting factor in the fluctuations in the mill window gap x. Therefore, the mill window gap x also fluctuates according to the amount of equipment wear. As shown in Figures 4(a) and (b), the amount of equipment wear dx is equal to the increase in the cylinder stroke, so the amount of hydraulic oil movement increases with the increase in stroke. By managing these increments dVa and dVb, dx and, in turn, the amount of equipment wear can be constantly monitored.

[0038] Figure 6 shows the change over time in the amount of hydraulic oil V required for the cylinder stroke for each strip threading. As explained above, the amount of oil represented on the vertical axis is proportional to the amount of cylinder stroke that restrains the roll chocks, i.e., it represents the mill window gap x. If the mill window gap x is between the control value L1 and the control allowable value L2, the rolling mill is judged to be normal and the strip is threaded. If the mill window gap x exceeds the control allowable value L2, an alarm is output and adjustment work for the mill window gap x is instructed. It is preferable to have a control device that controls these operations.

[0039] The mill window gap x can be adjusted, for example, as shown in Fig. 5(c). As shown in Figs. 5(a) and (b), liners 10 are installed on the window 9 surface of the housing 8 of the rolling mill and on the window forming equipment 5. The liners 10 manage the gap between the roll chocks 7 and the window 9 surface. For example, if this gap becomes larger than the allowable value due to equipment wear, as shown in Fig. 5(c), a gap adjustment shim 11 is attached to the housing liner 10a or the replacement rail liner 10b to adjust the gap amount. This improves the threading stability. [Industrial Applicability]

[0040] According to the rolling mill and rolling method of the present invention, malfunctions in the chock restraint device can be detected early, and since the mill window gap can be constantly monitored, equipment wear can be grasped and equipment can be appropriately managed, thereby reducing productivity impairment, and thus the rolling mill and rolling method are industrially useful. [Explanation of symbols]

[0041] 1 Hydraulic cylinder (chock restraint device) 1a Cylinder head side oil chamber (oil chamber) 1b Cylinder rod side oil chamber (oil chamber) 2a Head side hydraulic piping (hydraulic piping) 2b Rod side hydraulic piping (hydraulic piping) 3a Head side flow meter (flow meter) 3b Rod side flowmeter (flowmeter) 4 Hydraulic Valve Stand 5 Window configuration equipment 5a Replacement rail 6 rolls 6a Work Roll 6b Middle roll 6c Auxiliary roll (backup roll) 7 Roll Chock 8. Housing 9 Windows 10 Liner 10a Housing Liner 10b Replacement rail liner 11 Gap adjustment shim PL Pass Line WL Window Interval

Claims

1. the roll rolling rolling machine comprising a pair of upper and lower work rolls arranged above and below with a material to be rolled therebetween, a pair of upper and lower auxiliary rolls which are in direct contact with the work rolls, respectively, or which are in contact with the work rolls via a pair of upper and lower intermediate rolls which are in contact with the work rolls, respectively, a pair of roll chocks which rotatably support both ends of the work rolls, the intermediate rolls and the auxiliary rolls, respectively, and a pair of housings to which the roll chocks are attached with a gap provided therebetween, either directly or via a window-forming facility, The present invention has a chock restraining device that presses the roll chock toward the entry side or the exit side of the rolling direction of the material to be rolled, and a means for monitoring the extrusion amount of the chock restraining device, the chock restraining device is a hydraulic cylinder type device installed inside the housing or the window construction equipment; The amount of displacement is measured by integrating the flow rate of hydraulic oil and measuring the distance the piston moves. The hydraulic fluid is supplied to or withdrawn from the hydraulic cylinder device via a hydraulic circuit provided within the housing or the window construction equipment; A sensor for monitoring the volumetric flow rate of the hydraulic oil is provided in the hydraulic oil supply and recovery path; A rolling mill configured to determine equipment abnormalities by comparing the amount of oil on the cylinder side and the rod side of the hydraulic cylinder with threshold values ​​set for each cylinder operation position, or by comparing the amount of oil moving for each cylinder operation with a past value.

2. 2. A rolling method using the rolling mill according to claim 1, wherein at any time during rolling, the roll chocks are pressed toward the inlet side or the outlet side in the sheet passing direction of the rolled material, and the measured extrusion rate is compared with a predetermined value to determine an equipment abnormality.

3. 3. The rolling method according to claim 2, further comprising the steps of: outputting an alarm and adjusting the gap when the determined equipment abnormality is an increase in the gap.

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