JPH0615322A - Sheet crown control method at time of hot rolling - Google Patents

Abstract

PURPOSE:To obtain the target sheet crown while the occurrence of partial wear of work rolls is obviated. CONSTITUTION:In the CVC method using a hot rolling mill provided with a coupler of upper and lower work rolls 3 having prifiles of a bottle shape, respectively and arranged so as to be made to point symmetry mutually on a vertical cross section and a work roll bending device 2, the upper and lower work rolls 3, 3 are shifted in the axial direction in the reverse direction mutually for rolling material where the shift instruction positions for the upper and lower work rolls 3, 3 do not exceed the shiftable limiting position. The shift quantities of the upper and lower work rolls 3, 3 are then varied periodically in the shiftable range for the rolling material where the shift instruction positions for the upper and lower work rolls 3, 3 exceed the shiftable limiting position and the bending force by the work roll bending device 2 is given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling machine having a bottle-shaped profile and a pair of upper and lower work rolls arranged in point symmetry in a vertical cross section, and a work roll bending device. TECHNICAL FIELD The present invention relates to a plate crown control method during hot rolling, which performs axial plate thickness distribution (plate crown) control by shifting upper and lower work rolls in opposite axial directions in a machine and work roll bending control.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of steel sheets, it has been required to control the width direction plate thickness distribution, that is, the plate crown, as much as possible. Has evolved into a large diameter backup roll. On the other hand, in operation, the roll is provided with an initial crown to control the plate crown.

However, the change of the initial crown cannot be easily performed because the roll is changed. Therefore, in order to perform plate crown control and shape control, a roll bending apparatus has been developed which bends a roll by an external force to compensate for roll wear and roll deflection during rolling.

Since the roll bending apparatus can give a correction to the rolls at any time during rolling in response to the rolling load, it is much superior to the means for providing the initial crown in terms of the controllability of the plate crown. As is well known, a work roll bender (WR
B) and a backup roll vendor (BURB).

By the way, in recent years, sheet crown / shape control has become more and more important due to the need for higher dimensional accuracy and higher quality of products in hot rolling. On the other hand, from an operational perspective, schedule-free operation is also aimed at in order to achieve short delivery times and high efficiency. The above-described plate crown control means alone has not been sufficient to meet these demands.

Therefore, as a means for controlling the plate crown with higher precision, a roll shift method or a roll shift method using a roll bending function in combination has been proposed and has already been partially put into practical use.

For example, by shifting the intermediate roll of a six-fold rolling mill consisting of a backup roll, an intermediate roll and a work roll in the axial direction according to the strip width of the rolled material and adjusting the bending force of the work roll bending device. A so-called HC mill that controls the plate crown, and two sets of work rolls and backup rolls that roll in conformity with the axial direction are arranged with their respective rotation axes intersecting each other in the horizontal plane, and are supported by two backup rolls. There is known a so-called pair cross (PC) mill that controls a plate crown by axially shifting upper and lower work rolls relative to each other.

However, these rolling mills are not only expensive because they have a complicated structure, but also when the existing rolling mill is remodeled, the remodeling period becomes extremely long, which hinders the daily production of products. However, there are many problems such as difficulty in remodeling due to dimensional restrictions due to the installation location of the existing rolling mill.

As a rolling mill which has a low equipment cost, can be easily modified, and has a large plate crown control capability,
JP-A-57-91807, 63-20106, 63-
No. 84712 and 63-84713 disclose a rolling mill provided with a pair of upper and lower work rolls, each of which is provided with an initial crown of substantially the same shape and arranged so as to be point-symmetric with respect to each other in a vertical cross section. A technique has been proposed in which the upper and lower work rolls are axially shifted in opposite directions to control the plate crown.

For example, JP-A-63-84712 or 63
-84713, the work roll axial shift amount is set appropriately for each rolled material by the shape of the upper and lower work rolls, and the work roll axial shift amount is set by using a work roll bender together. Techniques have been proposed for obtaining the desired plate crown while minimizing it. FIG. 2 (a) is a graph showing an example of setting work roll shift and work roll vendor by these techniques.

In FIG. 2 (a), the shift set value is the set value of the shift amount for each rolled material to achieve the plate crown target value calculated according to the rolling schedule, and similarly, the bend force set value is It is a set value of the bending force for each rolled material for compensating / minimizing the shift set value. In Fig. 2 (a), the bending force is 200 ton / cho in the 1st to 12th rolling.
ck is constantly given, and the plate crown is controlled to a target value by appropriately changing the shift set value for each rolled material. However, since the control amount of the plate crown increases at the 13th to 27th rolls, it is necessary to set the shift set value to the maximum along with the bend force set value.During this time, the work roll is fixed at the shift upper limit position, and the 28th roll is set. After that, the control amount of the plate crown is reduced, and the work roll is no longer fixed at the shift upper limit position, and is shifted below the shift upper limit position.

However, this technique does not take into consideration work roll wear dispersion and heat crown dispersion. That is, during the 13th to 27th rolling in FIG. 2 (a),
Since the work roll remains fixed at the shift upper limit position, partial wear occurs on the work roll, and the work roll profile changes rapidly at the boundary between the contact area and the non-contact area with the rolled material. It becomes impossible to control the plate crown of the rolled material that is rolled to the target value.

Japanese Patent Laid-Open No. 2-179308 discloses a bottle shape as shown in FIG. 3 in order to mitigate partial wear of the work roll and its heat crown in consideration of wear roll wear dispersion and heat crown dispersion. By using a pair of upper and lower work rolls 3 and 3 having a profile of, the upper and lower work rolls 3 and 3 are axially shifted in opposite directions from each other by a predetermined amount from the work roll shift position at the time of rolling the preceding material. A technique has been proposed in which the work rolls 3 are shifted to different places for each rolled material and rolling is performed. In the figure, 1 is a backup roll,
2 conceptually shows the work roll bending device, 4
Indicates a rolled material.

This technique is based on the shift set value shown in FIG.
As shown in the graph of FIG. 2 (b), the wear dispersion shift amount that cyclically changes by a predetermined amount in the axial direction, and the equivalent bending force are added to the bending force setting value, This is a technique for obtaining the shift command value and the bending force command value shown in c), performing work roll shift and work roll bending based on these command values, and controlling the plate crown. According to this plate crown control method, the effects of work roll wear and heat crown can be significantly reduced.

[0015]

By the way, both the work roll bender amount and the work roll shift amount cannot be set indefinitely, and in reality, there are equipment limit values. FIG. 4 shows the shift locus and the shiftable limit position (set as a soft end) of the work roll during the 21st to 28th rolling in the method proposed by Japanese Patent Application Laid-Open No. 2-179308 shown in the graph of FIG. 2 (c). FIG. 4 is an explanatory diagram showing an example of a horizontal plane. For example, before the 20th roll in Fig. 2 (c), since the shift signal output from the computer is within the shiftable limit range (0 to 300 mm), the work roll moves within the shiftable limit range according to this signal. To do. In Fig. 4, the shift limit position is set as a soft end at a position ± 150 mm outside the rolling mill from the shift center position.

In the 21st to 28th lines in FIG. 2 (c), the work roll shift position for obtaining the target plate crown is the position indicated by a circle in FIG. 4, but it is proposed by JP-A-2-179308. In order to prevent partial wear, the work roll shift position should be, for example, + 155m.
Values exceeding the shiftable limit position such as m, +160 mm, and +170 mm (marked with ● in Fig. 4) are continuously output from the computer. Therefore, the work roll is fixed to the shift upper limit value for equipment protection (marked by X in FIG. 4), and thus the occurrence of partial wear of the work roll cannot be eliminated.

That is, although the method proposed by Japanese Patent Laid-Open No. 2-179308 can certainly reduce the occurrence of partial wear as compared with the conventional method, the work roll is always shifted in the axial direction to completely eliminate the occurrence of partial wear. It cannot be resolved.

Further, as is apparent from FIG. 2 (c), in this method, a work roll bending device is always used to apply a bending force to the work roll for compensating the plate crown. Accordingly, it is necessary to rapidly increase or decrease the set value of the actuator that constitutes a part of the drive system for the work roll shift. Therefore, problems such as a delayed reaction of the actuator and an error between compensations occur, and it is necessary to improve the problem.

Here, the object of the present invention is to provide a light emitting device disclosed in JP-A-2-1793.
An object of the present invention is to provide a plate crown control method at the time of hot rolling, which is capable of obtaining a target plate crown while eliminating the occurrence of partial wear of work rolls by improving the method proposed by Japanese Patent Publication No. 08.

[0020]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that (i) when the work roll does not reach the shiftable limit position, the rolling schedule is changed according to the rolling schedule. The work roll is shifted for each rolled material to maintain the reduction condition for obtaining the target plate crown, and (ii) the work roll shift signal exceeding the shift limit position is output and the work roll is fixed at the shift limit position. In this case, in order to eliminate the fixed state of the work roll, the work roll can be moved within the shift limit range, for example, the shift limit position ~ (50 mm above the shift limit position.
The work roll shifts beyond the shiftable limit position by reciprocally moving the upper and lower work rolls in the axial direction (about the inside) and applying the bending force by the work roll bending device to maintain the rolling condition to obtain the target plate crown. It was found that the occurrence of partial wear of the work roll can be completely eliminated even when a signal is output.

Further, when the work rolls do not reach the shiftable limit position, the present inventors periodically reverse the upper and lower work rolls from each other by a predetermined amount from the work roll shift position at the time of rolling the preceding material. It has been found that the direction may be shifted in the axial direction.

Further, the present inventors have found that the work roll shift amount may be periodically increased or decreased by periodically changing the shiftable limit position by a predetermined amount. Based on these findings, the present inventors have conducted further diligent studies and completed the present invention.

Here, the gist of the present invention is to provide a pair of upper and lower work rolls each having a bottle-shaped profile and arranged so as to be point-symmetrical to each other in a vertical cross section, and a work roll bending device. Using the provided hot rolling mill, hot rolling to obtain the target plate crown by performing plate crown control and work roll bending control by axially shifting the upper and lower work rolls in opposite directions for each rolled material. (I) For the rolled material in which the shift instruction position for the upper and lower work rolls does not exceed the shiftable limit position, the upper and lower work rolls are axially shifted in opposite directions. Maintaining the reduction condition to obtain the target plate crown, (ii) the shift instruction position for the upper and lower work rolls is at the shiftable limit. For rolled material exceeding 0.1 mm, the amount of shift of the upper and lower work rolls is periodically increased / decreased within the shiftable range and the bending force by the work roll bending device is applied to maintain the reduction condition for obtaining the target plate crown. This is a method for controlling a plate crown during hot rolling.

Further, in the above-mentioned present invention, the shift amount for the rolled material in which the shift instruction position for the upper and lower work rolls does not exceed the shiftable limit position is only a predetermined amount from the work roll shift position during the preceding material rolling. It may be changed periodically.

FIG. 1 is an explanatory view showing an example of a work roll shift locus and a shiftable limit position (set as a soft end) in a horizontal plane in a method for controlling a plate crown during hot rolling according to the present invention. In the figure, the circles, the circles, and the crosses have the same meanings as in FIG. The shiftable limit position is the same as in FIG.

According to the present invention, the work roll that has reached the shiftable limit position is periodically increased / decreased by a predetermined amount (50 mm in FIG. 1) within the shiftable range, as indicated by the mark X. Fixing of the work roll at the shiftable limit position described with reference to FIG. 4 can be eliminated. Therefore, according to the present invention, it is possible to eliminate the partial wear that occurs in the work roll.

Further, the alternate long and short dash line in FIG. 1 predetermines the shift amount for the rolled material in which the shift instruction position for the upper and lower work rolls does not exceed the shiftable limit position from the shift position of the work roll during the preceding material rolling. The locus | trajectory of a work roll at the time of cyclically changing only the amount is shown. In this case, the shift amount of the work roll in the axial direction is slightly narrowed, but the behavior reaches exactly the virtual shift possible limit position (indicated by the broken line) provided slightly inside, and the behavior is exactly the same as shifting by a certain amount. .

In the present invention, the shift amount may be periodically increased or decreased without any particular limitation. For example, as shown in FIG. 1, the shiftable limit position may be changed by a predetermined amount (50 mm in FIG. 1), or when the shift instruction position to the work roll exceeds the shiftable limit position. May output a signal to the work roll to increase / decrease the shift amount at a constant cycle within the shiftable range to cancel fixing the work roll to the shiftable limit position.

[0029]

The operation of the present invention will be described in detail below. The present invention is an improvement of the invention proposed by Japanese Patent Laid-Open No. 2-179308, and an object thereof is to eliminate partial wear caused by a fixed state of a work roll at a shiftable limit position.

The point of the present invention is, roughly speaking, provided with a pair of upper and lower work rolls each having a bottle-shaped profile and arranged so as to be point-symmetrical to each other in a vertical cross section, and a work roll bending device. A hot rolling mill is used to obtain the target strip crown by performing strip roll control and work roll bending control by axially shifting the upper and lower work rolls in opposite directions for each rolled material. (I) For the rolled material in which the shift instruction position for the upper and lower work rolls does not exceed the shiftable limit position, by shifting the upper and lower work rolls in opposite axial directions, Maintaining the rolling condition to obtain the target plate crown, (ii) the shift instruction position for the upper and lower work rolls reaches the shift limit position. In order to maintain the reduction condition for obtaining the target plate crown, the upper and lower work roll shift amounts are periodically increased / decreased within the shiftable range and the bending force by the work roll bending device is applied to the rolled material. It is in.

That is, it is possible to prevent the paired upper and lower work rolls having the bottle-shaped profile from being fixed at the shiftable limit position by periodically increasing or decreasing the shift amount of the work rolls within the shiftable range. ,
Therefore, partial wear due to the work roll being fixed is prevented.

In the present invention, the means / control for periodically increasing / decreasing the work roll shift amount within the shiftable range does not require any limitation, and any known method in relation to the control system for shifting the work roll is known. It may be by means. For example, I. When a shift instruction value that exceeds the shiftable limit position is output, the shiftable limit position (soft end) that is pre-installed in the program that controls the axial shift of the work roll is shifted. Within the possible range, for example, means for periodically increasing / decreasing within the range from the shiftable limit position to (about 50 mm inside the shiftable limit position), or II. When a shift instruction value exceeding the shiftable limit position is output. Can exemplify means for changing the shift instruction value so as to periodically increase or decrease by a predetermined amount within the aforementioned shiftable range without changing the soft end.

In any case, it suffices if the fixed state of the upper and lower work rolls at the shift limit position can be eliminated. Next, the control method according to the present invention will be described more specifically while comparing it with a conventional control method.

FIG. 5 is an explanatory view showing a method of calculating a crown control amount in the plate crown control method at the time of hot rolling proposed by JP-A-2-179308, and FIG. 5 (a) is a plate crown control. 5B is a flowchart showing an example of a calculation procedure for determining the axial work roll shift amount given to the pair of upper and lower work rolls.

In the apparatus for performing plate crown control shown in FIG. 5 (a), the CPU is selected during automatic operation, and the CPU performs crown control and oscillation control for control. The following will be divided.

Crown Control FIG. 6 is a perspective view showing an outline of an example of a rolling mill used for performing this control. The device shown in the figure uses a cylinder via arms 6a to 6d to perform crown control.
Work rolls 7a and 7b having a bottle-shaped profile can be axially shifted by 5a to 5d. Further, work roll bending devices 8a to 8d are installed at both ends of the work rolls 7a and 7b. For example, the work roll body length: 1780 mm, the maximum value of the work roll diameter-the minimum value: 0.5 mm, the distance between the maximum and minimum work roll diameters in the roll body length direction: 1040 mm, the backup roll (not shown) body length: 1780 mm, the work roll is -89, where x is the axial coordinate and y is the width coordinate.
In the range of 0 ≤ x ≤ +890 (mm),

[0037]

[Equation 1]

It is represented by The configuration itself of the rolling mill shown in FIG. 6 is known from Japanese Patent Application Laid-Open No. 2-179308 and the like, and therefore further description is omitted.

Oscillation control Work roll wear, roll heat-up calculation and target delivery side plate crown amount are calculated, and the work roll shift amount is calculated in accordance with these. The procedure for calculating the work roll shift amount Δi will be briefly described below with reference to FIG. In Fig. 5 (b), roll wear profile C _W (z)
, Roll heat-up crown C _H (z), and target value of each stand output side plate crown Ci are calculated by the following equations.

[0040]

[Equation 2]

[0041]

[Equation 3]

[0042]

[Equation 4]

Where α is the coefficient of linear expansion of the work roll,
N: Number of rollings, B: Strip width, P: Rolling load, D: Roll diameter, L: Rolling length, z: Coordinates in the same direction, ls: Shift amount, R: Roll radius, ν: Poisson's ratio, θ: Roll temperature, θ ₀ : initial roll temperature, r: radial coordinate, C: plate crown amount, h: outlet plate thickness, η: plastic flow coefficient,
α _max : a steepness constraint value. Note that the initial Ci starts from the neutral set value of the actuator and is changed / converged so as to reduce ΔCi.

In order to realize each stand output side plate crown target value Ci calculated in this way, the work roll shift amount δi is tentatively determined, and the δi changeable amount is calculated for the tentatively determined δi. Here, an example of the relationship between the shift amount δi and the work roll bending force is shown in a graph in FIG.

FIG. 7 shows the effect of work roll bender force (ton / chock), work roll crown (mm / diameter) or work roll shift amount (mm) on the rolled plate crown.
It is a graph which shows the result of having calculated the influence of (micrometer) by the conditions of board width: 1200mm, load: 1.5ton / min, and backup roll crown: 0. From the figure, there is a linear relationship between the shift amount δi and the work roll bending force,
In the example shown in the figure, it can be seen that there is a relationship of 150 mm shift = 200 ton / CH vendor. Therefore, the variable amount of δi can be calculated using this relationship by the work roll vendor (Min value − Max
Value) can be calculated.

Here, for δ, the set value at the time of the previous rolling is compared with the calculated value at this time, it is confirmed that they do not show the same value, and δi is finally determined. If they show the same value, they are set to δi + α.

Then, by using the divided model, various influence coefficients at δi (for example, the influence coefficient of the load at point j on the backup roll and work roll on the axial deflection of point i, and the load at point j on the work roll are Calculate the influence coefficient on the surface displacement at point i, the plate crown influence coefficient at the vendor, etc.) and set WRB and VC to achieve Ci while considering the flatness.

In this way, conventionally, the shift amount of the work roll in the axial direction has been controlled. In brief, the shift amount is determined by the work roll partial wear of the work roll shift amount, the work roll bender, and the equivalent crown change amount of the VC roll calculated based on the calculation results of the crown change amount. The total shift amount is determined by adding the shift amounts set to eliminate the above.

However, as described above, when the shift amount δi is determined in this way, (a) a fixing measure at the shift possible limit position that causes partial wear of the work roll, in other words, to the shift possible limit position. Since no measures are taken to eliminate the work roll fixed state, and (b) the work roll bending force is constantly changed according to the shift amount, the amount of setting change between rolling materials increases, There was a problem that an error was likely to occur in the applied work roll bending force, and a particular problem was unavoidable.

Therefore, in order to solve such a problem, in the present invention, as described with reference to FIG.
To decide. In the example shown in FIG. 8, the shiftable upper limit position (soft end) is periodically increased / decreased within a shiftable range by a predetermined amount (50 mm) to periodically increase / decrease the shift amount of the upper and lower work rolls. This is the case. That is, while the shift instruction position for the upper and lower work rolls exceeds the shiftable limit position (between points A and B in the figure),
By periodically increasing or decreasing the work roll shift amount within the shiftable range, it is possible to prevent the upper and lower work rolls from being fixed at the shiftable limit position, and during this period, the reduction amount of the work roll shift amount is compensated. Then, a bend force set value is appropriately given in order to obtain a desired plate crown amount.

That is, according to the present invention, in the control shown in FIG. 5 (b), the work roll shift possible limit range that periodically changes is inquired at the stage of temporarily determining the shift amount δi, and the shift position is within this range. Be inside.

As described above, according to the plate crown control of the present invention shown in the graph of FIG. 8, when the shift position of the upper and lower work rolls reaches the shift upper limit position, the shift amount is periodically increased and decreased and the bending force is increased. Overlay.
When the bending force of the work roll is other than the above, it is not necessary to perform the overlapping. In other words, while the shift instruction value exceeding the shiftable limit position is being output to the work roll, the work roll shift amount is periodically changed within the shiftable range and in the vicinity of the shiftable limit position. Fluctuation and imparting bending force with a work roll bending device.

As a concrete means for shifting the work roll in the axial direction, for example, based on the limit value of the actuator flexible range, the stroke end of the cylinder for shifting the work roll can be set as a soft end. Limit position (5 from shift limit position
(Position up to about 0 mm inward) can be exemplified cyclically and over time (oscillation). According to this aspect, the work roll fixing state at the shiftable limit position can be eliminated, and this occurs in the work roll. Partial wear can be eliminated.

On the other hand, when the shift instruction position with respect to the work roll does not exceed the shiftable limit position, Japanese Patent Laid-Open No. HEI-2 is used.
It is not necessary to calculate and set a shift position capable of maintaining a desired plate crown and to increase or decrease the shift amount with time as described above, as in the method proposed by Japanese Patent Laid-Open No. 179308. However, even in such a case, it is desirable to increase / decrease the shift amount periodically to shift the work roll in the axial direction because the partial wear generated in the work roll can be further reduced.

As described above, according to the present invention, the work roll is not fixed to the shiftable limit position during rolling, and the partial wear of the work roll can be eliminated. Further, according to the present invention, the period in which the work roll bending force is applied to the upper and lower work rolls is significantly shortened as compared with the conventional case, so that the temperature drop of the work rolls can be reduced as much as possible. Further, the present invention will be described in detail with reference to examples, but this is an example of the present invention and the present invention is not limited thereto.

[0056]

[Example] The method according to the present invention was applied to the F _{1 to} F ₄ stands, which are the preceding stages of the finish rolling stand, to perform strip crown control during hot rolling. The work roll shift amount and the work roll bending value of each of the stands F1 to F4 are summarized in Table 1.

[0057]

[Table 1]

FIG. 9 shows about 20 roll chances of hot rolling.
10 is a graph showing the loci of shift positions of the work rolls F _{1 to} F ₄ between 00 tons, and in FIG. 9, the shiftable limit position of the work rolls is 0 when the number of F1 and F2 stands is 10 to 40. It was periodically increased or decreased within the range of ~ 50 mm. From the figure, in the rolled material of 10 to 40 rolls, according to the present invention, the shift setting position of the work roll is appropriately increased or decreased and set, and the work roll is fixed to the shiftable limit position (position of 0 mm). I was able to completely eliminate the situation.

FIG. 10 is a graph showing an example of the situation of partial wear of the work roll in both the example of the plate crown control method proposed by JP-A-2-179308 and the example of the present invention under the same rolling conditions. , FIG. 10 (a) is disclosed in JP-A-2-
An example of the control method proposed by Japanese Patent No. 179308 is shown in FIG. 10 (b).
Are examples of the present invention.

As is apparent from the figure, according to the conventional method, the time for rolling with the work roll fixed at the shiftable limit position cannot be eliminated, so that partial wear occurs at the portion A. On the other hand, according to the present invention, it is understood that the unevenness of the wear profile of the work roll is reduced and the depth of partial wear of the B portion is reduced as compared with the conventional control method.

Further, FIG. 11 shows a comparative example (41 to 65 pieces) in which a work roll is fixed and examples of the present invention (0 to 40, 66 to 120).
The results of the (actual value-target value) of the plate crown are shown while comparing with (the book). From the figure, according to the present invention,
It can be seen that the crown control accuracy is good.

[0062]

As described in detail above, according to the present invention,
So-called CVC proposed by Japanese Patent Laid-Open No. 2-179308
In the method, it became possible to obtain the target plate crown while eliminating the occurrence of partial wear of the work roll.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a work roll shift locus and a shift possible limit position (set as a soft end) in a horizontal plane according to the present invention.

FIG. 2 is a graph showing a setting example of a work roll shift and a work roll vendor according to a conventional technique, and FIG.
Is the shift setting amount and bending force setting value set by the technique proposed in Japanese Patent Laid-Open No. 63-84712 or 63-84713, and Fig. 2 (b) considers wear dispersion and heat crown dispersion. 2 (c) shows the shift command value and the bend force command value set by the technique proposed by Japanese Patent Laid-Open No. 2-179308.

FIG. 3 is an explanatory view showing an example of a hot rolling mill proposed by JP-A-2-179308.

FIG. 4 is a graph of FIG. 2 (c) showing a method proposed by Japanese Patent Laid-Open No. 2-179308, in which the work roll shift locus and the shiftable limit position (set as a soft end) during the 21st to 28th rolling. FIG. 4 is an explanatory diagram showing an example of a horizontal plane.

FIG. 5 is an explanatory view showing a method of calculating a crown control amount in a plate crown control method at the time of hot rolling proposed by Japanese Patent Laid-Open No. 2-179308, and FIG. 5 (a) shows the entire plate crown control. FIG. 5B is a flowchart showing an example of a calculation procedure for determining the axial work roll shift amount given to the pair of upper and lower work rolls.

FIG. 6 is a perspective view showing an outline of an example of a rolling mill used to perform the control shown in FIG.

[Fig. 7] The effect of strip crown (μm) after rolling on work roll bender force (ton / chock), work roll crown (mm / diameter) or work roll shift amount (mm), strip width: 1200 mm, load 5 is a graph showing the results obtained by calculation under the conditions of: 1.5 ton / min and backup roll crown: 0.

FIG. 8 is an explanatory diagram showing an example of a method of determining a work roll shift amount δi in the present invention.

FIG. 9 is a graph showing a locus of shift positions of work rolls F _{1 to} F ₄ during one roll chance of hot rolling of about 2000 tons.

FIG. 10 is a graph showing an example of the work roll wear state in both the example of the plate crown control method proposed by JP-A-2-179308 and the example of the present invention under the same rolling condition, and FIG. An example of the control method proposed by Japanese Patent Laid-Open No. 2-179308 and an example of the present invention are shown in FIG. 10 (b).

FIG. 11: Comparative example with fixed work rolls (41 to 65 rolls)
It is a graph which shows the result of having calculated | required (actual value-target value) of a plate crown, comparing this invention example (0-40, 66-120 pieces).

[Explanation of symbols]

1: Backup roll 2: Work roll bending device 3: Work roll 4: Rolled material 5a to 5d: Cylinder 6a to 6d: Arm 7a to 7b: Work roll 8a to 8d: Work roll bending device

Claims (3)

[Claims] 1. A hot rolling mill equipped with a pair of upper and lower work rolls each having a bottle-shaped profile and arranged so as to be point-symmetrical to each other in a vertical cross section, and a work roll bending device, A strip crown control method at the time of hot rolling to obtain a target strip crown by performing strip roll control and work roll bending control by axially shifting the upper and lower work rolls in opposite directions for each material. , (I) For a rolled material in which the shift instruction position for the upper and lower work rolls does not exceed the shiftable limit position, the upper and lower work rolls are axially shifted in opposite directions to each other to obtain a target plate crown. The condition is maintained, and (ii) the rolling instruction position for the upper and lower work rolls is applied to the rolled material exceeding the shiftable limit position. In addition, by periodically increasing or decreasing the shift amount of the upper and lower work rolls within a shiftable range and applying a bending force by the work roll bending device, it is possible to maintain a reduction condition for obtaining a target plate crown. Method for controlling strip crown during hot rolling. 2. A shift amount for a rolled material in which the shift instruction position for the upper and lower work rolls does not exceed a shiftable limit position is periodically determined by a predetermined amount from the shift position of the work roll during rolling of the preceding material. The method of controlling a strip crown during hot rolling according to claim 1, wherein the method is changed. 3. The plate during hot rolling according to claim 1, wherein the cyclic increase / decrease of the shift amount is performed by cyclically changing the shiftable limit position by a predetermined amount. Crown control method.