WO2009142211A1

WO2009142211A1 - Method of diagnosing roll

Info

Publication number: WO2009142211A1
Application number: PCT/JP2009/059216
Authority: WO
Inventors: 保雄丸木; 潤哉岩崎; 悟山條; 孝幸矢野; 隆西原; 孝之白神
Original assignee: 新日本製鐵株式会社
Priority date: 2008-05-19
Filing date: 2009-05-19
Publication date: 2009-11-26
Also published as: BRPI0912766A2; KR101332950B1; CN102036770B; CN102036770A; JP5217620B2; KR20100139143A; JP2009274130A

Abstract

Disclosed is a method of diagnosing a pair of rolls disposed opposite to each other on both sides of a cast piece passage in a continuous casting machine. The method comprises a step of providing the result of measurement by measuring multiple times the interval between the pair of rolls when a dummy bar passes the cast piece passage at time intervals, a step of providing the trend of the time series of the differential values between the result of measurement and reference values, and a step of predicting a time at which the differential values reach or exceed a predetermined value according to the trend of the time series and determining the time when the pair of rolls break.

Description

Role diagnosis method

The present invention relates to a roll diagnosis method for knowing in advance the roll replacement time in a continuous casting machine.
This application claims priority on May 19, 2008 based on Japanese Patent Application No. 2008-130466 filed in Japan, the contents of which are incorporated herein by reference.

The continuous casting machine is provided with a plurality of roll pairs (guide rolls) arranged along the slab passage. The slab passes through the slab passage while being guided by these roll pairs. By the way, if an abnormality occurs in the interval between the roll pairs, there is a possibility that quality deterioration such as center segregation or internal crack of the slab may be caused. For this reason, it is extremely important to properly maintain the interval between the roll pairs, and for that purpose, the interval between the roll pairs has been conventionally measured (for example, see

Patent Documents

1 and 2 below).

¡Factors affecting roll spacing include roll bearing anomalies, roll wear, and roll bending. Among these factors, the abnormality of the roll bearing has a great influence on the gap between the rolls. Therefore, in the technique described in Patent Document 2 below, the measurement for one roll is performed at a plurality of locations, and the measurement is performed once. Using the obtained measurement data at a plurality of locations, the presence or absence of breakage of the roll bearing is detected.

JP-A-10-274502 JP 2006-231350 A

If the measured value of the roll interval exceeds the allowable value, the rolls of this roll pair are inspected, and if there are any abnormalities in the roll bearings, the rolls are replaced at that time. However, even if the value of the roll interval is less than the allowable value, an abnormality occurs in the roll bearing or the like during continuous casting, and as a result, flaws are produced in the manufactured slab. There is an abnormality, and it may be found that the roll bearing or the like is hindered. In this case, there is a problem that defective slabs are manufactured in large quantities. Therefore, it is desired to estimate the roll replacement life by estimating the life of the roll bearing.

From this point of view, the above Patent Document 1 discloses an apparatus for measuring the interval between roll pairs, but the point of estimating the roll replacement time by estimating the life of the roll bearing, We do not disclose anything. Moreover, in the said patent document 2, although the detection precision of the presence or absence of breakage of a roll bearing increased by judging using the measurement data in several places obtained by one measurement, a failure time is predicted beforehand. It was not reached.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a roll diagnosis method capable of solving the above-described problem by predicting in advance the breakage time of a roll mainly caused by a roll bearing. .

The present invention employs the following means in order to solve the above problems and achieve the object. That is,
(1) The roll diagnosis method of the present invention is a method of diagnosing a pair of rolls that are opposed to each other with a slab passage of a continuous casting machine interposed therebetween, and the roll when a dummy bar passes through the slab passage. Obtaining a measurement result by measuring a pair interval several times over time; obtaining a time series tendency of a difference value between the measurement result and a reference value; and based on the time series tendency, the difference Predicting a time when the value is equal to or greater than a predetermined value, and determining the time as a time when the roll pair is broken.

According to the present inventors, the roll bearing supporting the roll gradually wears and deteriorates, and accordingly, the roll interval gradually deviates from the reference value. Moreover, it has been found that the difference value between the measured value and the reference value tends to increase in proportion to time, and this difference value suddenly increases from a certain point on the time axis and breaks. The present invention has been made on the basis of such knowledge, first, the interval between the opposed roll pairs is measured a plurality of times over time, and data relating to the roll interval for each roll pair is time-series. To collect. Then, the time series tendency of the difference value between the measurement result and the reference value is examined, and based on this time series tendency, a time when the difference value is equal to or greater than a predetermined value is predicted, and this time is determined as a roll breakage. Judging that it is time. Therefore, it is possible to know when the roll is replaced before the roll bearing is damaged.

As the predetermined value, for example, when the roll bearing is actually damaged, the interval value of the roll pair having the roll bearing is measured in advance, and the difference value between the interval value and the reference value at this time is adopted. May be. In this case, there are a plurality of roll pairs that are opposed to each other with the slab passage of the continuous casting machine in between, and the load varies depending on the installation location. Is different. Therefore, it is preferable to determine the predetermined value for each pair of rolls.

(2) The roll diagnosis method according to (1) may further include a step of notifying a warning when the difference value reaches or exceeds a first reference value smaller than the predetermined value.
Examples of the warning notification mentioned here include display such as lighting of a lamp to notify through vision, and sounding of a buzzer to notify through hearing. As a result, for example, a warning is given before the roll bearing supporting the roll is damaged, so that the roll bearing can be replaced more reliably.

(3) The roll diagnosis method according to (1) may further include a step of measuring a tilt of the roll pair.
In this case, the tilt of the roll can also be detected at the same time. The inclination of the roll here refers to the inclination of the slab passage formed by the surfaces of the rolls arranged side by side, specifically, the predetermined position of each roll forming the predetermined slab passage. It is represented by the amount of misalignment (misalignment amount).
(4) In the case of (3) above, the method may further include a step of notifying a warning when the inclination reaches the second reference value or more.

(5) In the case of (1) above, the method may further include a step of detecting rotation and non-rotation of the roll pair.
In this case, the rotation / non-rotation of the roll pair can be detected simultaneously.
(6) In the case of the above (5), a step of notifying a warning when non-rotation of the roll pair is detected may be further provided.

According to the present invention, it is possible to predict in advance the roll breakage mainly due to the roll bearing, and it is possible to replace the roll before breakage.

It is a side view which shows a mode when the dummy bar equipped with the roll space | interval measuring apparatus for performing one Embodiment of the roll diagnostic method of this invention passes the slab path | route of a continuous casting machine. It is a bottom view of the dummy bar. It is a longitudinal cross-sectional view of the said roll space | interval measuring apparatus. It is a figure which shows the sensor head and sensor housing in the same roll space | interval measuring apparatus, Comprising: It is an expanded sectional view of the A section of FIG. It is a top view of the sensor head. It is a longitudinal cross-sectional view which shows a state when the said roll space | interval measuring apparatus is contacting the roll. It is a figure which shows a mode that the foreign material entered into the receiving part of the said roll space | interval measuring apparatus, Comprising: It is an expanded sectional view of the B section of FIG. It is a side view which shows the outline | summary of a roll alignment sensor typically. It is a side view which shows typically the outline | summary of a roll inversion sensor. It is a block diagram which shows typically the outline | summary of the system for enforcing the said roll diagnostic method. It is the graph which showed one roll space | interval measured value for every roll pair, Comprising: The horizontal axis shows the number of each roll pair, and a vertical axis | shaft shows the measured value of the space | interval of each roll pair. In the No. 49 roll pair, it is a graph showing the difference value between the roll pair interval and the reference value with the increase in the number of charges, the horizontal axis is the number of online charges, the vertical axis is the roll pair interval and the reference value Indicates the difference value. It is a graph which shows the measurement result about the inclination of a roll in No. 29 to No. 34 roll pairs, the horizontal axis shows the roll pair number, and the vertical axis shows the misalignment amount. It is the graph which displayed the signal from the roll inversion sensor for every cast by a rotation rate about a specific roll, a horizontal axis shows a cast number and a vertical axis shows a rotation rate.

One embodiment of the roll diagnosis method of the present invention will be described below.
FIG. 1 is a side view schematically showing a dummy bar 1 equipped with a roll interval measuring device for performing the roll diagnosis method of the present embodiment. The dummy bar 1 has a large number of link members 1 a and shafts 1 b, and a slab formed between a plurality of

rolls

4 and 5 by leading a molten steel 3 cast from a tundish (not shown) through a mold 2. Move through the aisle.

FIG. 2 shows the bottom surface of the dummy bar 1 on which the roll interval measuring device is mounted. In the present embodiment,

sensor units

7a, 7b, and 7c are provided at both ends in the width direction and the center of the sensor link 6 of the dummy bar 1, respectively. Each of these

sensor units

7a, 7b, 7c is provided with one roll interval measuring device S. The

sensor units

7a and 7b at both ends are further provided with a roll alignment sensor Q for measuring the inclination of the

rolls

4 and 5, and a roll inversion sensor R for detecting the rotation / non-rotation of the roll.

Since the roll interval measuring devices S provided in each of the

sensor units

7a, 7b, and 7c all have the same configuration, in the following description, as an example of the roll interval measuring device S provided in the sensor unit 7a. This will be described in detail with reference to FIG.
The roll interval measuring device S has

sensor devices

10 and 20 for measuring the interval between the roll pairs 4 and 5 facing the top and bottom surfaces thereof. The sensor device 10 on the upper surface side is for measuring the displacement of the roll 4 on the movable surface side, and the sensor device 20 provided on the bottom surface side is for measuring the displacement of the roll 5 on the fixed surface side. . The distance between the

rolls

4 and 5 is measured based on the measurement result of the displacement measured by both the

sensor devices

10 and 20.

As shown in FIG. 3, the sensor device 10 is fixed to both the sensor head 11 in contact with the roll 4; the main body of the sensor unit 7 a and the connecting member 30, and has a cylindrical shape that houses the sensor head 11. And a sensor housing 12.

The sensor head 11 includes a cylindrical main body portion 11a; a head portion 11b having a conical shape on the upper portion of the main body portion 11a and having a shape in which the top portion is convexly curved toward the roll 4; have. A spring 13 is arranged along the vertical direction of the paper surface between the locking portion 11c formed inside the sensor head 11 and the connecting portion 30, and the sensor head 11 is located above the paper surface relative to the sensor housing 12, that is, It is urging toward the roll 4. A flange portion 11 d is formed at the lower end of the sensor head 11. Since the flange portion 11 d is locked to the locking portion 12 a of the sensor housing 12, the sensor head 11 does not come out of the sensor housing 12. A detection rod 14 is provided at the center of the sensor head 11. The upper end of the detection rod 14 is in contact with the lower surface of the head portion 11b, and the detection rod 14 also moves up and down as the head portion 11b moves up and down, and this movement is transmitted to the displacement meter 15 so as to be detected. It has become.

And between the lower end of the head part 11b and the upper end of the main-body part 11a in the sensor head 11, as shown in FIG. 4, the cyclic | annular step part 11e is formed. In the present embodiment, the width dimension d (see FIG. 5) of the step portion 11e is set to 0.5 mm.

As shown in FIG. 3, the sensor device 20 that measures the amount of displacement with respect to the reference position on the roll 5 side also has substantially the same configuration as the sensor device 10. That is, the sensor device 20 includes: a sensor head 21 that comes into contact with the roll 5; a cylindrical sensor housing 22 that is fixed to both the main body of the sensor unit 7a and the connecting member 30 and that houses the sensor head 21 therein. I have. The sensor head 21 includes a cylindrical main body portion 21 a and a head portion 21 b that is curved so that the top portion is convex toward the roll 5. In addition, a spring 23 is disposed between the engaging portion 21c and the connecting portion 30 inside the sensor head 21, and the sensor head 21 moves vertically downward with respect to the sensor housing 22 (that is, on the roll 5 side). (Towards). A detection rod 24 is provided at the center in the sensor head 21. The lower end of the detection rod 24 is in contact with the upper surface of the head portion 21b, and the detection rod 24 also moves up and down as the head portion 21b moves up and down, and this movement is transmitted to the displacement meter 25 so as to be detected. It has become.

According to the roll interval measuring device S having the above-described configuration, the dummy bar 1 on which the roll interval measuring device S is mounted leads the molten steel 3 and passes through the slab passage formed by the plurality of

rolls

4 and 5. As it moves, the sensor head 11 of the sensor device 10 comes into contact with each roll 4 and the sensor head 21 of the sensor device 20 comes into contact with each roll 5, thereby measuring the distance between the roll pairs 4, 5. To go.

As for the sensor device 10, as shown in FIG. 6, the sensor head 11 in contact with the roll 4 is pushed down against the urging force of the spring 13 and stored in the sensor housing 12. Then, as shown in FIG. 7, when the lower end of the head portion 11 b of the sensor head 11 enters the sensor housing 12, the gap between the outer peripheral surface of the lower end of the head portion 11 b and the inner peripheral surface of the upper end of the sensor housing 12. By the step portion 11e formed in the above, an annular receiving portion AP is formed in which the bottom surface shape is an annular band in plan view and the vertical cross-sectional shape is an inverted trapezoid.

Therefore, when the dummy bar 1 moves in the slab passage, foreign matter x such as a coolant or scale is generated, and the gap between the outer peripheral surface of the head portion 11 b of the sensor head 11 and the inner peripheral surface of the sensor housing 12 is generated. Even if it enters, this foreign substance x is received by the receiving part AP. The vertical cross-sectional shape of the receiving part AP is not a tapered shape (tapered or V-shaped) with a sharp tip as in the prior art, but is an inverted trapezoid as described above. That is, it is received by the step portion 11e. Therefore, as the dummy bar 1 advances, the contact of the sensor head 11 with the roll 4 ends, and when the sensor head 11 is returned to the original position by the spring 13, the foreign matter x is directly moved out of the sensor housing 12 by the step portion 11e. It is pushed out. Accordingly, the sensor head 11 can be smoothly returned to the original position without the occurrence of the biting phenomenon of the foreign matter x as in the prior art. Therefore, it is possible to accurately measure the roll interval stably over a long period of time. Moreover, since the protrusion length itself from the sensor housing 12 of the sensor head 11 is not different from the conventional one, the safety of the sensor head 11 is ensured as it is.

In addition, since the foreign matter adhering to the roll of the continuous casting machine is generally less than 0.5 mm, in the above embodiment, the width dimension d of the step portion 11e constituting the bottom surface of the receiving portion AP is set to 0.5 mm. Preferably, 0.5 mm to 2 mm, for example, about 1 mm is desirable.
Further, the step portion 11e of the present embodiment, when viewed in the enlarged cross-sectional view shown in FIG. 7, the bottom surface 11e1 that is the annular plane, and the bottom surface 11e1 is continuous with the bottom surface 11e1 and goes upward in the vertical direction. The sensor housing 12 is formed by an inclined surface 11e2 that is gradually separated from the inner peripheral surface of the upper end. Therefore, even if a relatively large foreign object x of 0.5 mm or more enters the receiving portion AP, the restoring force when the sensor head 11 returns upward by the urging force of the spring 13 and the inclination angle of the inclined surface 11e2 This large foreign matter x can be effectively pushed out of the receiving part AP.

Next, the roll alignment sensor Q will be described with reference to FIG. The roll alignment sensor Q has a contact 41 that receives an urging force and projects downward from the lower surfaces of the

sensor units

7a and 7b. The contact 41 is in contact with each of the rolls on the fixed surface side (that is, the pair of

rolls

5 and 5 adjacent to each other along the direction of the slab passage, and the inclination between the rolls 5 and 5 (that is, , The inclination between the

rolls

5 and 5 forming the lower surface of the slab passage) is detected by the amount of deviation of these

rolls

5 and 5 from a predetermined position.

As shown in FIG. 9, the roll inversion sensor R includes, in its main body, a roll contact body 51 that rotates in contact with the roll 4; and a roll contact body 52 that rotates in contact with the roll 5. Yes. When the

rolls

4 and 5 are rotating, the

roll contact bodies

51 and 52 rotate in the direction opposite to the rotation direction of the

rolls

4 and 5, but when the

rolls

4 and 5 are in a non-rotating state, the

roll contact bodies

51 and 52 rotate in the reverse direction. . Therefore, the rotation / non-rotation of the

rolls

4 and 5 can be detected by detecting the rotation angle (rotation rate) of the

rolls

4 and 5 with a detector (not shown).

Each of the signals detected by the roll interval measuring device S, the roll alignment sensor Q, and the roll non-rotation sensor R described above is a signal processing unit 8 mounted on the link material 1a in the vicinity of the sensor link 6 (FIG. 2). Output).

As shown in FIG. 10, the signal output from the signal processing unit 8 mounted on the dummy bar 1 is output to the host computer 61 in the central operation room, and further sent to the server 63 in the central operation room via the HUB 62. And stored in the server 63. Then, a measurement result for each roll obtained every time the dummy bar 1 passes through the slab passage is processed and accumulated for each roll.

Software necessary for data analysis is installed in the server 63, and for the roll interval, the time series tendency of the difference value between the measurement result obtained in advance and the reference value is calculated. Then, based on this time series trend, a time when the difference value is equal to or greater than a predetermined value is predicted by extrapolation. Further, as a result of the measurement, when the difference value becomes equal to or greater than a predetermined reference value smaller than the predetermined value, an alarm signal is output to an alarm means (not shown). As for the signal from the roll alignment sensor Q, an alarm signal is output to the alarm means when the misalignment amount based on the output signal for each roll becomes a predetermined value or more. As for the signal from the roll inversion sensor R, an alarm signal is output to the alarm means when the rotation rate based on the output signal for each roll becomes a predetermined value or more.

The server 63 can be connected from a plurality of

monitoring client terminals

65 and 66 via the router 64. Therefore, the role diagnosis method of this embodiment can be performed from outside the central operation room using the

monitoring client terminals

65 and 66 as necessary.

The main apparatus and system configuration for performing the role diagnosis method of the present embodiment are as described above. Hereinafter, examples of the roll diagnosis method will be described.

FIG. 11 shows one roll interval measurement value from the roll interval measuring device S mounted on the dummy bar 1 for each roll pair. The measurement value of the first roll is set to 0 and each roll pair interval is shown. The measured value is displayed. According to this, it turns out that there is variation in the roll interval of each roll pair installed in the continuous casting machine. However, this data alone does not reveal the tendency of rolls to deteriorate over time. Therefore, paying attention to a specific roll pair, for example, the 49th roll pair, the 49th roll pair is measured a plurality of times at intervals, and the difference value from the reference value is calculated. Shown in 12 graphs.

The horizontal axis in the graph of FIG. 12 indicates the number of online charges, and the vertical axis indicates the difference value between the measured value and the reference value. The number of on-line charges is the number of times molten steel is poured into the tundish from the ladle, so it is not directly related to the number of measurements when the dummy bar 1 passes through the slab passage, and is a graph showing the actual measurement time point. The number of plots in the middle indicates the number of measurements. The black circle in the graph indicates the roll interval on one end side of the roll (specifically, the fixed side roll bearing side), and the black triangle in the graph indicates the other end side of the roll (specifically, the free side). The roll interval on the roll bearing side) is shown. These are based on data from the roll interval measuring device S mounted on the

sensor units

7 a and 7 b provided on both sides of the sensor link 6. That is, the graph of FIG. 12 is a plot of the difference value from the reference value of the roll pair interval near both ends of the roll pair.

According to the graph of FIG. 12, the difference value between the roll pair interval on the free side and the roll bearing side and the reference value is approximately 0.6 mm. On the other hand, the difference between the roll pair interval on the fixed side and the roll bearing side and the reference value increases in proportion to the increase in the number of charges, reaches 1.0 mm at approximately 36500 charges, and then increases rapidly. You can see that As a result of verification at a later date, it was confirmed that the roll bearing was damaged when the difference value from the reference value was 1.0 mm or more in this roll.

Accordingly, the roll interval is measured a plurality of times over time, the difference value between these measurement values and the reference value is calculated, and further, the time series tendency of this difference value is examined, so that the difference value becomes 1.0 mm or more. The accumulated charge number can be predicted. The time of the accumulated charge number obtained in this way can be predicted as the roll bearing breakage time. Therefore, it is possible to replace the roll bearing before the time of the accumulated charge number comes.

Further, in the present embodiment, when the difference value between the measurement result and the reference value is less than the predetermined value and equal to or more than the predetermined reference value in the server 63, an alarm signal is output. Therefore, for example, an alarm signal can be output when the difference value becomes 0.9 mm. As a result, it is possible to identify in advance a roll whose roll bearing will be damaged in the near future, and to replace this roll in advance.

In this embodiment, the dummy alignment bar 1 is mounted with a roll alignment sensor Q that measures the tilt of the roll. Therefore, the tilt of the roll can also be monitored by the server 63 and the

monitoring client terminals

65 and 66.

FIG. 13 is a graph of roll tilt measurement data for rolls No. 29 to No. 34. According to this graph, it can be seen that a misalignment (positional deviation) in which the deviation from the predetermined position exceeds the allowable value occurs for the 31st roll. In the server 63, an alarm signal is output when the value exceeds a predetermined reference value. Therefore, when the positional deviation amount exceeds a predetermined reference value, this can be known. . Therefore, it is possible to perform replacement and maintenance of the corresponding roll in advance. In addition, since rolls whose positional deviation is equal to or greater than the specified reference value are identified, this is far more than when the equipment is stopped and the operator manually checks all rolls as before. The time required for role discovery and handling can be shortened. Therefore, productivity can be improved.

Furthermore, in this embodiment, since the roll inversion sensor R for detecting the rotation / non-rotation of the roll is mounted on the dummy bar 1, whether or not the

rolls

4 and 5 are rotating during continuous casting, Monitoring can be performed by the server 63 and the

monitoring client terminals

65 and 66.

FIG. 14 shows the rotation rate of the signal from the roll inversion sensor R for each specific roll for each cast (that is, every time the dummy bar 1 leads the molten steel and passes through the slab passage of the continuous casting machine). It is displayed.

According to this, at the time of the sixth cast, the rotation rate has reached 80% or more. After the sixth cast, the rotation rate changes between 70% and 80% until the segment supporting the roll is replaced. Then, after the 10th cast is completed, the rotation rate is reduced to about 15% in the 11th cast after the corresponding roll is exchanged by exchanging the segments. In this embodiment, the roll is not determined to rotate when the rotation rate exceeds 20%.

As a result of actual verification, it is possible to confirm the slab crease in the slab produced by the continuous casting of the sixth cast, and the slab crease in the slab produced by the continuous casting after the 11th cast. Could not be confirmed.

Further, in this embodiment, rotation / non-rotation detection data is output to the server 63 for each roll, and an alarm signal is output when the output signal value for each roll exceeds a predetermined value. It has become. Therefore, for example, by setting a rotation rate of 20% as the predetermined value, it is possible to immediately know a roll in which non-rotation has occurred. Therefore, as in the conventional case, after the slab oyster is found in the manufactured slab, the facility is stopped, and the operator manually checks the rotation / non-rotation of the roll for all the rolls. In comparison, the non-rotating roll can be found very easily and in a short time, and the equipment stop time can be shortened, thereby improving the productivity.

The present invention is useful for diagnosis of a roll of a continuous casting apparatus.

DESCRIPTION OF SYMBOLS 1 Dummy bar 1a Link material 1b Shaft 2 Mold 3 Molten steel 4 Roll 5 Roll 6

Sensor link

7a, 7b, 7c Sensor unit 8 Signal processing unit 10 Sensor apparatus 11 Sensor head

11a Body part

11b Head part

11c Locking part

11d Flange part

11e Stage Part 12 Sensor housing

12a Locking part

12b Step part 13 Spring 14 Detection rod 15 Displacement meter 20 Sensor device 21 Sensor head

21a Body part

21b Head part

11c Locking part 22 Sensor housing 23 Spring 24 Detection rod 25 Displacement gauge 30 Connecting member 51 Roll contact body 52 Roll contact body 61 Host computer 62 HUB
63 Server 64 Router 64
65, 66 Monitoring client terminal AP receiving part D Transport direction Q Roll alignment sensor R Roll inversion sensor S Roll interval measuring device d Width x Foreign object

Claims

A method for diagnosing a roll pair disposed opposite to each other with a slab passage of a continuous casting machine interposed therebetween,
Measuring the interval between the pair of rolls when a dummy bar passes through the slab passage a plurality of times, and obtaining a measurement result;
Obtaining a time series tendency of a difference value between the measurement result and a reference value;
Predicting a time when the difference value is equal to or greater than a predetermined value based on the time-series trend, and determining this time as a break time of the roll pair;
A roll diagnosis method comprising:
The roll diagnosis method according to claim 1, further comprising a step of notifying a warning when the difference value reaches or exceeds a first reference value smaller than the predetermined value.
The roll diagnosis method according to claim 1, further comprising a step of measuring an inclination of the roll pair.
The roll diagnosis method according to claim 3, further comprising a step of notifying a warning when the inclination reaches a second reference value or more.
The roll diagnosis method according to claim 1, further comprising a step of detecting rotation and non-rotation of the roll pair.
6. The roll diagnosis method according to claim 5, further comprising a step of notifying a warning when non-rotation of the roll pair is detected.