JP5261971B2 - Roll gap measuring device for work roll of rolling mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roll gap measurement device capable of measuring a roll gap with high accuracy and applicable even to a crown control mill in a cross roll rolling mill or the like. <P>SOLUTION: The outer circumferential part of at least either work roll of the upper and lower work rolls 1a, 1b is equipped with: an eddy current type distance sensor 5 provided not so as to interfere with a backup roll and the material to be rolled; and a slipping mechanism 6 for performing the feed of electric power to the eddy current type distance sensor 5 and the extraction of a measured signal in the eddy current type distance sensor 5. The eddy current type distance sensor 5 provided at the outer circumferential part of either work roll can magnetically measure the shortest distance with the other work roll with high accuracy, thus a roll gap can be measured with high accuracy without receiving the influence of disturbance, and further, it can be applied even to a crown control mill in a cross roll rolling mill or the like. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a roll gap measuring device for a work roll of a rolling mill, a rolling mill using this device, and a method for producing a hot-rolled steel strip.

  In recent years, in the field of continuous hot rolling and the like, various crown control mills such as a pair cross roll rolling mill have been put into practical use, and as a result, it has become possible to stably produce a flat steel strip without a plate crown. However, the steel strip is more likely to meander during rolling as much as the plate crown becomes smaller, especially when the tail end of the material to be rolled (hereinafter referred to as “hot rolled steel strip” for convenience) falls out. A new problem has arisen in that the steel strip collides with the side guides, falls down, and is rolled. Improving the passability of the tail end portion of the hot-rolled steel strip in a hot-rolling finishing mill is a very important issue for improving the operating rate and the roll basic unit.

  The meandering phenomenon of a hot-rolled steel strip in a rolling mill is generally said to have a second-order integral characteristic. FIG. 14 shows the physical interpretation, and FIG. 14 (A) is a view of the moment when the tail end of the steel strip passes through the work roll as viewed from above. For example, when the hot-rolled steel strip meanders, the rolling load on the side where the steel strip has approached becomes higher than one as shown in FIG. Naturally, since the narrow side of the roll gap is rolled thinner than the other, it is elongated longer in the rolling direction, and the sheet passing speed is slower than the other. For this reason, as shown in FIG. 14 (A), the steel strip bends in a dogleg shape with the rolling part as a boundary. Once the steel strip is bent, the amount of meandering from there increases with time. Thereby, as shown in FIG. 14 (B), when the plate path is removed from the roll center, the mill elongation in the direction in which the steel strip is bent (right direction in FIG. 14 (B)) increases, and the roll gap opens, As shown in FIG. 14C, by further promoting the deflection, a meandering amount proportional to the square of time is generated.

  In order to avoid such problems, a typical hot-rolled steel strip meandering control technique is proportional to cancel the left-right roll opening difference Sdf generated by the left-right difference Pdf of the rolling load of the rolling mill as shown in FIG. This is meander control (parallel stiffness control) for moving the leveling correction amount SL by control. In FIG. 15, α is a control gain (0 to 1), and M is a parallel stiffness. This meandering control technique is a method (generally referred to as leveling operation) for controlling the leveling correction amount SL of a rolling mill reduction device (screw, hydraulic cylinder, etc.) in a direction to suppress meandering according to the following equation (i). . In the following formulas (i) to (iii), α is a control gain, Pdf is a left-right difference in rolling load (hereinafter referred to as “differential load Pdf”), Sdf is a difference in opening between left and right rolls, and M is parallel rigidity or Left and right rigidity, L is the distance between the left and right rolling devices, and yc is the amount of deviation of the center of the hot rolled steel strip relative to the center in the width direction of the hot rolling line (hereinafter simply referred to as “meandering amount yc”).

The parallel stiffness or the left / right stiffness M is represented by the ratio of the differential load Pdf and the left / right roll opening difference Sdf at the reduction device position, as shown in the following equation (ii). Further, the relationship between the meandering amount yc and the differential load Pdf is expressed by the following equation (iii). That is, in a rolling mill with a high parallel rigidity M, the left-right roll opening difference Sdf due to the differential load Pdf is less likely to occur, and the differential load generated by the meandering amount yc of the material to be rolled due to the relationship shown in the following formula (iii). The left and right roll opening difference Sdf due to Pdf is also less likely to occur.
SL = -α (Pdf / M) (i)
M = Pdf / Sdf (ii)
yc = (Pdf · L) / 2P = (Sdf · L) / (2P · M) (iii)

  As shown in the above formula (iii), the meandering amount yc of the material to be rolled and the differential load Pdf are in a proportional relationship. However, in actual rolling, there are many other factors that generate the differential load. For example, left and right plate thickness difference of the material to be rolled, left and right temperature difference (≒ left and right plastic constant difference), left and right spring constant difference due to corrosion and wear deterioration of rolling mill, thrust force between rolls due to parallelism deviation of work roll and backup roll And so on. In order to monitor all the factors of the differential load, a plurality of sensors are required corresponding to each factor, resulting in a large introduction cost and maintenance cost. Further, the meandering amount yc shown in the above formula (iii) is in the region to be rolled sandwiched between the upper and lower work rolls. For example, when providing a meandering sensor, inevitably to avoid interference with the work rolls. Since it is necessary to install at a position retracted several meters from the rolled region, it is difficult to directly measure the meandering amount yc in the rolled region.

  For the above reasons, it is practically difficult to extract only the differential load due to the meandering amount yc from a plurality of differential load factors, and it is necessary to perform the reduction position control based on the differential load Pdf which is the sum of all the factors. there were. Therefore, if meandering control is performed assuming that the differential load Pdf generated during rolling is entirely due to the meandering amount yc, the reduction position control becomes over-controlled due to the differential load fluctuation due to other factors, conversely, the narrowing trouble is promoted. Therefore, there is a problem that the current control gain α has to be set low depending on the rolling conditions, and therefore the trouble of narrowing down due to the tail end meandering cannot be solved completely.

  As a means to solve this, instead of meandering control based on the differential load Pdf, a proposal has been made to directly measure the roll gap of the upper and lower work rolls and to perform leveling control so that the left-right difference of the roll gap becomes zero. (Patent Document 1). This idea is a very natural idea, but the problem is that it is extremely difficult to measure. Many roll gap measuring means have been proposed so far, and typical methods include an optical type (for example, Patent Documents 2 to 4) and a mechanical type (for example, Patent Documents 5 to 8).

JP-A-6-297013 JP-A 62-198705 Japanese Patent Laid-Open No. 6-147843 Japanese Patent Laid-Open No. 57-132009 JP-A-64-31508 JP 58-199610 A Japanese Patent Laid-Open No. 57-137012 JP-A 64-78608

  The optical roll gap measurement means measures the roll gap based on the signal input to the light receiving device installed on the other side of the roll gap by placing a light source on either the entry side or the exit side of the roll gap. To do. However, the surroundings of the hot rolling mill are filled with steam and cooling water. Even if light projection and reception are performed for measurement in such an environment, high accuracy is achieved due to a decrease in the amount of light due to steam and noise in the received light due to water droplets. It is difficult to measure this, and it is necessary to take measures for sealing steam and cooling water to ensure a clear optical path.

  On the other hand, the mechanical roll gap measuring means interposes a mechanism for measuring the distance between the roll necks of the upper and lower work rolls or between roll chocks, and there is almost no influence on the measurement accuracy due to steam or cooling water. However, there is a restriction that the axis of the upper and lower work rolls must be on the same vertical line in order to measure the shortest distance between the upper and lower roll necks or the roll chock. On the other hand, in recent years, a cross roll rolling mill, which is one of the crown control mills in practical use, displaces the upper right and lower left roll chock or the lower right and upper left roll chock in the rolling direction as shown in FIG. In this method, the upper and lower work rolls are crossed and the cross angle is controlled in accordance with the required product steel strip crown shape. Therefore, the conventional mechanical roll gap measuring means cannot be applied to the crown control mill which is the main method in recent years.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and to measure the roll gap with high accuracy without being affected by disturbances such as steam and cooling water. An object of the present invention is to provide a roll gap measuring device applicable to a crown control mill such as the above.
Another object of the present invention is to provide a rolling mill capable of performing stable rolling using such a roll gap measuring device.
Furthermore, another object of the present invention is to produce a hot-rolled steel strip having a good shape by using such a rolling mill and to perform stable meandering control so that hot-rolled steel does not cause a drawing trouble. It is providing the manufacturing method of the hot-rolled steel strip which can manufacture a strip | belt stably.

As a result of repeated studies to solve the above problems, the inventors of the present invention directly attached the eddy current type distance sensor to the outer periphery of the work roll, and supplied power and took out the measurement signal via the slip ring. A roll gap measuring device has been devised that can measure the roll gap without being affected by water and cooling water, and can be applied to various crown control mills.
That is, the gist of the present invention is as follows.

[1] A roll gap measuring device for a work roll in a hot finish rolling mill for producing a hot-rolled steel strip,
An eddy current distance sensor provided on the outer periphery of the upper work roll of the upper and lower work rolls so as not to interfere with the backup roll and the material to be rolled, power supply to the eddy current distance sensor, and measurement signal of the eddy current distance sensor A slip ring mechanism for taking out
The eddy current type distance sensor is disposed in a recess formed on the outer peripheral surface of the upper work roll,
The slip ring mechanism includes a plurality of current collecting rings provided concentrically on an end surface of a roll body portion of an upper work roll, and a plurality of stationary brushes that are in sliding contact with the current collecting rings, respectively. The ring is insulated from the roll body by an insulator, and is electrically connected to the eddy current distance sensor by a lead wire disposed inside the roll. The brush is supported by the roll chock or the rolling mill housing, and the roll chock Alternatively, a power supply battery provided in a sensor box supported by the rolling mill housing is electrically connected to a power supply lead wire, and a wireless unit provided in the sensor box is electrically connected to a measurement signal transmission lead wire. roll gap measuring device of the rolling mill work rolls, characterized in that it is connected.

[2] A rolling mill having the roll gap measuring device according to [1] above at the left and right roll ends of a work roll.
[3] The rolling mill according to [2], wherein the rolling mill is a cross roll rolling mill.
[4] A method for producing a hot-rolled steel strip by hot-rolling a material to be rolled with the rolling mill according to [2] or [3 ] above, wherein a roll gap measuring device is used to roll right and left work rolls during rolling. A method for producing a hot-rolled steel strip, characterized in that a gap is measured and leveling control is performed so that a difference between left and right roll gaps becomes a target value.

According to the roll gap measuring device of the present invention, it is possible to measure the roll gap with high accuracy without being affected by disturbances such as steam and cooling water, and to a crown control mill such as a cross roll rolling mill. Can also be applied without problems.
Further, according to the rolling mill of the present invention using such a roll gap measuring device and a method for producing a hot-rolled steel strip using the same, high-precision leveling control in which the difference between the left and right roll gaps is monitored is easily performed. Therefore, it is possible to solve the problems of the current reduction position control based on the differential load Pdf, obtain a good hot-rolled steel strip shape, and cause a squeezing trouble by performing stable meandering control. The hot-rolled steel strip can be manufactured stably. For this reason, even in the production of thin hot-rolled steel strips, it is possible to secure a good steel strip shape and achieve stable threading, while improving line operation rate and roll unit consumption by reducing drawing trouble, High quality hot-rolled steel strip.

  FIGS. 1-6 shows one Embodiment at the time of applying the roll gap measuring apparatus of this invention to a hot finishing rolling mill, FIG. 1 shows the rolling mill work roll and backup roll in the case of zero roll gap. FIG. 2 is a partially cutaway side view (however, the slip ring mechanism is not shown), and FIG. 3 is a partially cutaway front view of a rolling mill work roll and a backup roll when there is a roll gap. 4 is a partially cutaway side view (however, the slip ring mechanism is not shown), FIG. 5 is a perspective view partially showing an upper work roll end portion to which a roll gap measuring device is attached, and FIG. It is a partially cutaway side view of the upper work roll (however, the slip ring mechanism is not shown).

  In the figure, 1a is the upper work roll, 3a is the roll chock, 1b is the lower work roll, 3b is the roll chock, 2a is the upper backup roll, 4a is the roll chock, 2b is the lower backup roll, and 4b is the roll chock. Further, 10a is a roll body portion of the upper work roll 1a, 11a is also a roll neck portion, 10b is a roll body portion of the lower work roll 1b, 11b is also a roll neck portion, and S is a material to be rolled.

In the rolling mill of this embodiment, the roll gap measuring device A is provided at each of the left and right roll ends of the upper work roll 1a. Each roll gap measuring device A includes an eddy current type distance sensor 5 provided on the outer periphery of the work roll so as not to interfere with the backup roll 2a and the material to be rolled S, and power supply to the eddy current type distance sensor 5 and an eddy current type. A slip ring mechanism 6 for taking out a measurement signal (output signal) of the distance sensor 5 is provided.
In the present embodiment, the concave portion 7 is formed on the outer peripheral surface of the upper work roll 1 a by counterboring or the like, and the vortex type distance sensor 5 (sensor head) is disposed in the concave portion 7. This eddy current type distance sensor 5 is provided in a state of being located inside the recess 7 by a distance δ ₀ from the surface of the upper work roll. The recess 7 may be a groove formed over the entire circumference of the roll. As the eddy current type distance sensor 5, a conventionally used sensor can be used.

  The slip ring mechanism 6 includes a plurality of current collecting rings 60 provided concentrically on the end surface of the roll body portion 10a of the upper work roll 1a, and a plurality of fixed-side brushes 61 that are in sliding contact with the current collecting rings 60, respectively. Multipolar type with As described above, the slip ring mechanism 6 used in the present invention has two or more poles in order to supply power to the eddy current type distance sensor 5 and transmit measurement signals of the eddy current type distance sensor 5 (signal extraction).

Each of the current collecting rings 60 is insulated from the roll main body by an insulator, and is electrically connected to the eddy current type distance sensor 5 by a lead wire 9 disposed inside the roll. The brush 61 is supported by a fixed portion such as a roll chock or a housing, and is electrically connected to a power source and a measurement signal processing system. In the present embodiment, lead wires (not shown) connected to the respective brushes 61 are drawn into the sensor box 8 supported by fixing parts such as the roll chock 3a and the housing (not shown). The sensor box 8 includes a battery for power supply and a wireless unit (both not shown), a lead wire for supplying power is connected to the battery, and a lead wire for measuring signal transmission is connected to the wireless unit. Yes.
The roll gap measuring device A may be provided on the lower work roll 1b, or may be provided on both the upper and lower work rolls 1a and 1b.

According to the roll gap measuring apparatus A as described above, a measurement signal as shown in FIG. 7 is obtained every time the eddy current type distance sensor 5 comes to a position facing the lower work roll 1b in one rotation cycle of the upper work roll 1a. The distance to the lower work roll 1b is measured based on the signal strength (voltage output). Here, for example, when the work roll is rotated with no roll gap as shown in FIG. 1 and FIG. 2, a measurement signal as shown in FIG. 7A is obtained. The distance δ ₀ is measured at the contact position of the rolls 1a and 1b. Therefore, by adjusting the minimum distance δ ₀ as the zero point of the sensor head, the measurement signal as shown in FIG. 7B obtained in the rolling state as shown in FIGS. From the measurement signal of δ (= roll gap) + distance δ ₀ , a roll gap measurement value is obtained. Further, the difference between the left and right roll gaps can be obtained by calculating the difference between the roll gap measurement values by the roll gap measuring device A arranged on the left and right sides of the rolling mill.

  FIG. 8 shows an outline of a cross roll rolling mill. As described above, the conventional mechanical roll gap measuring device requires that the upper and lower work roll axes be on the same vertical line, and thus In fact, it cannot be applied to any cross roll rolling mill. On the other hand, the roll gap measuring device of the present invention uses a vortex type distance sensor provided directly on the outer periphery of one work roll as the gap measuring means, and magnetically measures the distance to the other work roll. Therefore, it can cope with the displacement of the roll chock in the rolling direction, and therefore can be applied to a cross roll mill without any problem.

  FIG. 9 and FIG. 10 show one embodiment when the roll gap measuring device of the present invention is applied to a cross roll rolling mill (hot finish rolling mill), and FIG. 9 (A) shows a case where the roll gap is zero. FIG. 9B is also a side view (in this figure, the roll gap measuring device A should be originally represented by a broken line, but is represented by a solid line for convenience of explanation), FIG. 10 (A) is a front view of a rolling mill work roll and a backup roll when there is a roll gap, and FIG. 10 (A) is also a side view (in this figure, the roll gap measuring device A is supposed to be originally represented by a broken line. For the sake of convenience).

As described above, in this cross roll rolling machine, the upper and lower work rolls 1a and 1b are crossed in a plan view, so that the axes of the upper and lower work rolls 1a and 1b are not on the same vertical line. Since the configuration and function of the roll gap measuring apparatus A are the same as those of the embodiment shown in FIGS. 1 to 6, the same reference numerals are given and detailed description thereof is omitted.
When the roll gap measuring device A of the present invention is applied to such a cross roll rolling mill, the eddy current type distance sensor 4 provided on the upper work roll 1a can measure the shortest distance from the lower work roll 1b. Even if the axes of the rolls 1a and 1b are not on the same vertical line, their functions are not hindered. Here, for example, when the work roll is rotated with no roll gap as shown in FIG. 9, [the distance in the recess as shown in FIG. 6] + [the separation distance generated by crossing the rolls] A measurement signal of a certain distance δ ₀ is obtained. Therefore, by adjusting the minimum distance δ ₀ as the zero point of the sensor head, measurement of the distance δ (= distance proportional to the roll gap) + distance δ ₀ obtained in the rolling state as shown in FIG. A roll gap measurement is obtained from the signal. Further, the difference between the left and right roll gaps can be obtained by calculating the difference between the roll gap measurement values by the roll gap measuring device A arranged on the left and right sides of the rolling mill. Thus, the roll gap measuring device A of the present invention can be applied to a cross roll mill without any problem.

The rolling mill of this invention has the roll gap measuring apparatus A in the left-right roll end of a work roll like embodiment mentioned above.
Moreover, in the manufacturing method of the hot-rolled steel strip of this invention, when rolling a to-be-rolled material with such a rolling mill and manufacturing a hot-rolled steel plate, a roll gap measuring apparatus A is used for the work rolls 1a and 1b during rolling. The left and right roll gap is measured, and leveling control is performed so that the left and right roll gap difference becomes the target value. Specifically, leveling control is performed so that the difference between the left and right plate thicknesses (plate wedge) of the rolled material becomes zero, that is, the difference between the left and right roll gaps becomes zero.

  The roll gap measuring device of the present invention was installed in the final stand of the hot rolling finish rolling mill, and the roll gap during rolling was measured. FIG. 11 shows an equipment layout around the rolling mill during data measurement. In actual operation, the work roll needs to be replaced with a used roll and a new polished roll every 2-3 hours. It is necessary to take care not to stop it. In view of this, the roll gap measuring device is attached in advance to a polished new roll in a roll waiting state, and is incorporated into the rolling mill at the time of roll changing.

  Further, between the rolling mill and the outside thereof, wiring for the measurement signal and power supply of the eddy current type distance sensor 5 is required. However, as shown in FIG. 11, the power of the main motor is placed around the work roll on the drive side. Since the spindle for transmitting to the work roll is arranged, it is difficult to access for wiring work, and when performing the above wiring work, it is necessary to install a scaffold, and it is expected that a large line stop time will occur. . In order to solve these problems, the power source of the eddy current type distance sensor 5 is a small battery, and the measurement signal is data transmission using a wireless unit. For this purpose, a sensor provided with a small battery and a wireless unit in the roll chock 3a. Box 8 was attached. As described above, the wiring work for the measurement signal and the power source of the eddy current type distance sensor 5 which is normally required can be eliminated.

  FIG. 12 shows a flow of power supply to the eddy current distance sensor 5 and transmission of measurement signals from the eddy current distance sensor 5. In order to protect from the environment (steam, cooling water, temperature) around the rolling mill, a resin sensor box 8 is fixed to the roll chock 3a, and a small battery serving as a power source for the eddy current type distance sensor 5 is installed in the sensor box 8. A set of devices such as a transmission-side wireless unit that transmits a measurement signal of the eddy current type distance sensor 5 is housed. The power supply to the eddy current type distance sensor 5 and the measurement signal of the eddy current type distance sensor 5 are taken out via the slip ring mechanism 6, and the signal from the transmission side wireless unit is received on the safety passage outside the line. It was transmitted to the side wireless unit and recorded in the data logger.

  After confirming the output signal from the roll gap measuring apparatus A, leveling zero tone, which is usually performed after the roll change, was performed. Here, as shown in FIG. 1 and FIG. 2, leveling zero adjustment is performed in which the work roll is rotated in a state where the upper and lower work rolls are in contact with each other to adjust the left-right reduction position balance. At this time, the measurement signal of the eddy current type distance sensor 5 that fluctuates every roll rotation cycle is obtained, but the point where the measurement signal is minimum as described above is considered to be the state where the upper and lower work rolls are in contact with each other. Therefore, the minimum value of the left and right measurement signals at the time of zero leveling is considered to be the point where the left and right roll gap difference between the upper and lower work rolls becomes zero, and the left and right roll gap measuring device is zeroed.

In the rolling of hot-rolled steel strip, a total of 8 rollings under the same operating conditions (input side plate thickness h1 = 2.8 mm, output side plate thickness h0 = 2.0 mm, plate width b = 1200 mm) Data on the meandering amount yc based on the output of the installed meandering meter and roll gap data from the roll gap measuring device were collected. FIG. 13 shows the relationship between the meandering amount yc and the difference between the left and right roll gaps at the completion of rolling determined from the measurement results. Although a variation of about ± 20 μm was observed, a substantially linear correlation was observed between the two, and it was confirmed that highly reliable roll gap measurement was possible according to the present invention.
Furthermore, as a result of performing leveling control so that the difference between the left and right roll gaps becomes zero for a total of eight rollings under the same operating conditions, the rolling mill exit side meandering amount yc is 1/3 or less compared to the case without control. It was confirmed that it is effective for meandering control.

1 shows an embodiment when the roll gap measuring device of the present invention is applied to a hot finish rolling mill, and is a partially cutaway front view of a rolling mill work roll and a backup roll when the roll gap is zero. 1 is a partially cutaway side view of a rolling mill work roll and a backup roll when the roll gap is zero. 1 is a partially cutaway front view of a rolling mill work roll and a backup roll when there is a roll gap. 1 is a partially cutaway side view of a rolling mill work roll and a backup roll when there is a roll gap. FIG. 1 is a perspective view partially showing an upper work roll end portion to which a roll gap measuring device is attached in the embodiment of FIG. 1 is a partially cutaway side view of an upper work roll with a roll gap measuring device attached thereto. Explanatory drawing regarding the measurement signal obtained with the eddy current type distance sensor of the roll gap measuring device of the present invention Schematic perspective view of cross roll mill One embodiment at the time of applying the roll gap measuring device of the present invention to a cross roll rolling mill (hot finish rolling mill) is shown, and (A) shows a rolling mill work roll and a backup roll in the case of zero roll gap. Front view, (B) is also a side view (in this figure, roll gap measuring device A should be represented by a broken line, but is represented by a solid line for convenience of explanation) In the embodiment of FIG. 9, (A) is a front view of a rolling mill work roll and a backup roll when there is a roll gap, and (B) is also a side view (in this figure, the roll gap measuring device A is originally represented by a broken line. (It should be shown as a solid line for convenience.) Explanatory drawing which shows arrangement | positioning of this invention apparatus and measuring instrument in an Example Explanatory drawing which shows the flow about the electric power supply with respect to an eddy current type distance sensor, and transmission of the measurement signal of an eddy current type distance sensor in an Example. The graph which shows the relationship between the meandering amount yc of the rolling mill delivery side in an Example, and the left-right roll gap difference by this invention apparatus. Explanatory diagram showing physical interpretation of meandering phenomenon Explanatory diagram for explaining the concept of conventional parallel stiffness control for meandering

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Work roll 2a, 2b Backup roll 3a, 3b, 4a, 4b Roll chock 5 Eddy current type distance sensor 6 Slip ring mechanism 7 Recess 8 Sensor box 9 Lead wire 10a, 10b Roll body part 11a, 11b Roll neck part 60 Current collection Ring 61 Brush S Roll material A Roll gap measuring device

Claims (4)

A roll gap measuring device for a work roll in a hot finish rolling mill for producing a hot-rolled steel strip,
An eddy current distance sensor provided on the outer periphery of the upper work roll of the upper and lower work rolls so as not to interfere with the backup roll and the material to be rolled, power supply to the eddy current distance sensor, and measurement signal of the eddy current distance sensor A slip ring mechanism for taking out
The eddy current type distance sensor is disposed in a recess formed on the outer peripheral surface of the upper work roll,
The slip ring mechanism includes a plurality of current collecting rings provided concentrically on an end surface of a roll body portion of an upper work roll, and a plurality of stationary brushes that are in sliding contact with the current collecting rings, respectively. The ring is insulated from the roll body by an insulator, and is electrically connected to the eddy current distance sensor by a lead wire disposed inside the roll. The brush is supported by the roll chock or the rolling mill housing, and the roll chock Alternatively, a power supply battery provided in a sensor box supported by the rolling mill housing is electrically connected to a power supply lead wire, and a wireless unit provided in the sensor box is electrically connected to a measurement signal transmission lead wire. roll gap measuring device of the rolling mill work rolls, characterized in that it is connected.   A rolling mill comprising the roll gap measuring device according to claim 1 at left and right roll ends of a work roll.   The rolling mill according to claim 2, which is a cross roll rolling mill.   A method for producing a hot-rolled steel strip by hot-rolling a material to be rolled with the rolling mill according to claim 2 or 3, wherein a right and left roll gap of a work roll is measured by a roll gap measuring device during rolling. A method for producing a hot-rolled steel strip, wherein leveling control is performed so that the difference between the left and right roll gaps becomes a target value.

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