JPS62130710A - Plate thickness control method for steel stock - Google Patents

Abstract

PURPOSE:To make a plate thickness dimension highly accurate by correcting a rigidity value using an actually measured plate thickness of a steel stock rolled under a rolling load set based on an estimated value of the roll mill rigidity value and the plate thickness target value and resetting a rolling load. CONSTITUTION:An automatic plate thickness controller 26 calculates a screwing value based on an estimated mill rigidity value of a work roll. The controller 26 controls a hydraulic screwdown device 22 by the calculated screwing value. A plate thickness detector 32 measures a plate thickness of a rolled steel stock, sends the measured value to the controller 26 and a mill rigidity learning system 27, corrects the estimated mill rigidity value, obtains an actual mill rigidity value, and resets a rolling condition. The plate thickness dimensional accuracy is improved by controlling by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the thickness of a steel material by rolling the steel material to a predetermined thickness using a roll mill.

[Conventional technology]

In the cold rolling process, the steel material is rolled to a predetermined thickness by being passed through a roll mill. In this case, the roll mill sets the rolling load on the steel material according to the target plate thickness, but the set value of this rolling load is calculated by an automatic plate thickness control system (hereinafter referred to as AGC system) connected to the roll mill. ing. In the AGC system, the screw value is usually calculated based on the plate thickness formula shown in equation (1) below.

h=s, 10f・(P, W, DB, Dw, V)+δ・
...(1) However, h is the target plate thickness, S is the screw value of the roll mill, f is the coefficient, P is the rolling load, W is the plate thickness before rolling, DB is the roll diameter of the backup roll, Dw
is the roll diameter of the work roll, ■ is the rolling speed, and δ is the screw value correction value.

The method of calculating and controlling the screw value Sr of the roll mill based on equation (1) in this way is generally called the gauge meter method.

In this r-dimeter method, when the fluctuation range of the rolling load P is narrow, the coefficient f is considered to be a linear type with respect to P, so
The coefficient f can be expressed by the following equation (2).

/= P-M-(W, D, , Dw, V)
・=−・・−・(2) However, M is mill stiffness.

In this equation (2), when the rolling load changes by ΔP, the control amount ΔSr of the screw value of the roll mill is as follows (3
) is shown by the formula.

ΔS=-M・ΔP ・・・・・・・・・
(3) After the start of rolling, set the rolling load at an appropriate point to the standard value P
, the actual measured value is P, and the deviation from this Po is ΔP, then
ΔP is calculated by the following equation (4).

Δp = p − po ...
(4) The method of substituting equation (4) into equation (3) to calculate the negative value ΔS is called gauge meter AGC. Furthermore, by directly substituting the measured value P into the equation (1), the following equation (5) can be obtained. this(
5) In order to achieve the target plate thickness in formula 5, the method of determining the roll mill's scratch and -value S is by using the absolute value AGC・゜
It is called.

Sr= h −/(P)−δ ・・・・・・
...(5) However, in both the gauge meter AGC method and the absolute value AGC method, if the estimated value M of mill stiffness causes an error with respect to the actual mill stiffness value i, as shown in equation (6) below. As a result, an error C with respect to the target plate thickness occurs.

−MC=ΔS・□ ・・・・・・・・・(6)
M The rolling conditions do not change significantly in a steady state after a predetermined period of time has passed after the start of rolling. That is, since the control amount ΔS of the screw value is relatively small 1i:c, the plate thickness error e with respect to mill steel properties is relatively small.

FIG. 2 shows the relationship between the mill rigidity error and the plate thickness error. In FIG. 2, the horizontal axis represents the plate thickness and the vertical axis represents the rolling load P. The mill stiffness is determined from the plasticity curve corresponding to the target plate thickness, but since there is an error between the actual mill stiffness M and the estimated mill stiffness M, when this estimated mill stiffness is used, the plate thickness error C However, when the roll mill bites into the steel material to be rolled, or when the plate thickness is changed during rolling, the rolling conditions vary greatly. Accordingly, the control amount ΔSr of the scratch becomes large, and as is clear from equation (6), the error in plate thickness based on the error in mill rigidity becomes a considerably large value. for example,
In a cold tandem mill, when the steel material to be rolled is bitten, as the tip of the steel material is bitten by each stand, the tension that the roll mill acts on the steel material in each stand increases from 0 to 97w x 20 to 20. Add. As a result, the rolling load exerted by the mill on the steel material is reduced. In this case, the AGC system automatically controls the screw value from about 0.5 to 1. Owm change. However, if an error occurs in the mill rigidity, for example, in the case of a 5% error, the plate thickness error C of the steel material to be rolled is calculated from equation (6), g =
(0,5~1.0)mlnX0.05=0.025~0
．． It will be 05m.

When such a plate thickness error occurs, the quality of the product deteriorates or the product becomes defective, and this defective portion is removed, causing a decrease in product yield.

Attempts have been made to improve the accuracy of mill stiffness estimates. For example, the plate thickness control method disclosed in JP-A-60-9512 focuses on the fact that mill rigidity changes depending on the magnitude of rolling load, and calculates the relationship between rolling load and mill rigidity in advance. Then, from this relationship, the mill rigidity according to the value of the rolling load is predicted, and this predicted value is used for r-dimeter type plate thickness control.

[Problem that the invention seeks to solve]

However, the Iron and Steel Institute of Japan, Special Report WL36 (September 1, 1985), “Theory and Practice of Plate Rolling”, No. 22
As described on page 3, mill rigidity is affected not only by the absolute value of the rolling load but also by multiple factors such as the dimensions of the rolls, the material of the rolls, the width of the rolled material, and the rolling speed. Therefore,
Even if mill rigidity is predicted or compensated for using only a single factor such as rolling load, mill rigidity cannot be accurately predicted or compensated for, so there is a problem that the plate thickness accuracy decreases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for controlling the thickness of a steel material that can obtain a highly accurate plate thickness.

[Means for solving the invention]

A method for controlling the thickness of a steel material according to the present invention is a method for controlling the thickness of a steel material by setting the rolling load of a roll mill. Set the rolling load of the roll mill to roll the steel material, measure the plate thickness after rolling, calculate the error between the target plate thickness value and the actual measurement value, and calculate the roll mill rigidity value based on the error value of the plate thickness. is corrected, and the roll mill rolling load is set again using the corrected mill rigidity value.

In the method for controlling the plate thickness of a steel material according to the present invention, when rolling is started, the tension of the steel material acts on the roll mill.

That is, the tension of the steel material acts on the roll mill at the same time as the biting occurs from the tensionless state before rolling. Due to such a change in tension, the mill steel column M as the rolling condition of the roll mill changes. That is, since an error occurs in the mill steel property value, it is necessary to correct the screw value Sr. In this case, Scri, −
If the amount of correction (amount of change) of the value S is ΔSr, the following (7)
This correction amount ΔSr can be determined by the formula.

Here, Δh is the amount of change when changing the thickness of the plate to be rolled during rolling. Therefore, at the time of biting, Δh is 0. ΔP is the amount of change in rolling load, and M is the actual mill steel property value.

On the other hand, the following equation (8) can be obtained from equation (6).

However, there is a time lag between the amount of change in the scratch value ΔSr and the actual measured value of the plate thickness after rolling because the plate thickness measurement detector is installed on the exit side of the tandem mill. Such a time shift is shown in FIG. In FIG. 3, the horizontal axis shows time, and the vertical axis shows the amount of change ΔSr in screw value and the amount of change in plate thickness. As is clear from this Figure 3.

The amount of change in screw value affects the change in plate thickness after time Δ has elapsed.

Therefore, in order to correct such a time difference, the time when the plate thickness after rolling is actually measured is t, the time difference between the time during rolling and the time when the plate thickness is measured is Δt, and the circumferential speed of the roll is If V is the distance between the roll mill and the plate thickness detector, t is the distance between the roll mill and the plate thickness detector, then the following equation (9) can be obtained from the above equation (8).

In this case, it can be determined by Δt=t7v.

That is, the actual mill stiffness value M can be obtained from the following equation by modifying equation (9).

The actual mill stiffness value M is determined from the estimated mill stiffness value M and the plate thickness error value C using the α1 equation, and this actual mill stiffness value is used in the above-mentioned equation (1) to calculate the screw value ΔSr again. Calculate and set.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 4 of the accompanying drawings.

As shown in FIG. 1, tandem mills 12, 14, and 16 are installed in the cold rolling line 10 along the sheet passing direction. Each tandem mill 12゜14.16 has a pair of nower rolls (roll mill) 1 that press the steel material from above and below.
8 are provided, and each work roll 18 is in rolling contact with a backup roll 19 that applies a rolling force.

Each tandem mill 12, 14, 16 is connected to a control unit 20 which sets the roll N degree (roll-to-roll cap) of the work rolls 18, respectively. This control unit 2
0 is connected to each tandem mill 12, 14, 16, but since they are approximately equal, tandem mill 120 is shown in
Only the control unit 20 will be explained.

The control unit 20 includes a hydraulic reduction device 22 that applies a reduction force to the work rolls 18 via a backup roll 19 in order to set the roll opening degree between the pair of work rolls 18; A roll opening degree detector 24 for detecting the roll opening degree is provided.

The hydraulic lowering device 22 and the roll opening degree detector 24 are each AG
C (automatic plate pressure control) device 26, and the roll opening degree detector 24 is further connected to Mill's constant M'/stem 22.

The AGC device 26 calculates based on the detected value from a predetermined detector, and controls the drive of the hydraulic pressure lowering device 22 according to this calculated value. On the other hand, the mill constant learning system 27 is connected to the AGC device 26, calculates an error in mill stiffness based on the detected value from a predetermined detector, and sends this error value to the AGC device as a data signal.

The work roll 18 is provided with a rolling load detector 28 that detects the rolling load applied to the work roll 18 by the hydraulic rolling device 22.

This work roll 18 is connected to the AGC device 26.
and sends a detection signal to the AGC device. A rotation speed detector 30 for detecting the rotation speed of the work roll 18 is further attached to the work roll 18. This rotation speed detector 3o is connected to a Mill constant learning system 27, and sends a detection signal to the Mill constant learning system.

A plate thickness detector 32 is provided on the exit side of the work roll 18 to measure the thickness of the steel material rolled by the work roll 18. This plate thickness detector 34 is connected to the Mill constant learning system 22 and the AGC device 26, and sends detection signals to each. A tension detector 34 is installed adjacent to the plate thickness detector 32 to measure the tension of the rolled steel material.

This tension detector 34 is connected to the AGC device 26 and
A detection signal is sent to the C device 26.

Next, the operation of this embodiment will be explained. When the steel material is conveyed to the cold rolling line 10, in the tandem mill 12,
The hydraulic rolling device 22 is operated to provide the work roll 18 with a predetermined rolling blade so as to roll this steel material to a target plate thickness. In this case, the AGC device 26 calculates the rolling load based on the above-mentioned equation (1). That is, the target plate thickness is determined using the formula (1), rolling load P, plate pressure before rolling W, roll diameter of backup roll 19, 7-/roll 18
By substituting the values of the roll diameter and rolling speed V, the scratch value of the roll mill, -value Sr, is calculated.

Note that the coefficient f is calculated from equation (2), but in this case,
As the mil degree stiffness value M of the work roll, an estimated value estimated from the material of the work roll is used.

In this manner, the AGC device 26 uses the estimated mill stiffness value M of the work roll to calculate the screw value Sr corresponding to the target plate thickness hK. Then, the AGC device 26 controls the hydraulic pressure reduction device 22 to the obtained screw value S.

Next, the steel material is bitten by the work rolls 18 and rolling is started. In this case, the roll opening degree detector 24 measures the gap between the work rolls 18 and sends the measured value to the AG
C device 26 and mill learning system 21. Furthermore, the rolling load detection 28 sends its measured value to the AGC device 26 . The roll rotation speed detector 30 sends its measurements to the mill learning system 21 .

The steel material rolled by the work rolls then moves to a plate thickness detector 32. The plate thickness detector 32 measures the plate thickness of the steel material after rolling, and sends the measured value to the AGC device 26 and the mill constant learning system 27.

The mill constant learning system 27 calculates the actual mill stiffness value M by correcting the estimated mill stiffness value based on the α1 formula described above. That is, the error ε between the plate thickness after rolling and the target plate thickness,
Modify the mill stiffness value from the amount of change in screw value.

This corrected mill stiffness value is sent to the AGC device 26.

The AGC device 26 converts this corrected mill stiffness value into the above-mentioned (
1) Newly calculate the screw value Sr using the formula. AG
The C device 26 issues a control signal to the hydraulic lowering device 22 to reset to a new screw value Sr.

The hydraulic lowering device 22 is reset and the backup roll J
A new reduction blade is applied to the work roll 18 via the roller 9. This new rolling blade continues to roll the steel material and then winds it into a coil.

Since the rolled steel material is rolled using the estimated mill steel properties at the start of rolling, off-dirge occurs at its tip.

When the off-gauge length of the tip of the coil was measured, the results shown in FIG. 4 were obtained. FIG. 4 shows the off-gauge length on the horizontal axis and the frequency on the vertical axis, and shows the case where a steel material is rolled in a cold rolling mill having five tandem mills. The solid line in FIG. 4 shows the present invention, and the broken line shows the conventional method. As is clear from FIG. 4, the conventional off-gauge length was an average Ion, but according to the present invention, it can be shortened to an average of 3 m.

This invention is not limited to the one embodiment described above, and can be modified in various ways without departing from the gist of the invention.

For example, the present invention is not limited to setting the rolling load of the roll mill again at the start of rolling of the steel material, but may also be used to change the target plate pressure of the steel material during rolling.

〔Effect of the invention〕

According to this invention, the roll mill rigidity value can be corrected simply by measuring the plate thickness of the steel material after rolling, and the rolling load of the roll mill is set again using the corrected mill stiffness value, so that high precision plate A thick steel material can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a cold rolling mill according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between mill rigidity error and plate thickness error, and Fig. 3 is a change in scratch value. FIG. 4 is a graph showing the time delay between the change in plate pressure and the change in plate pressure. FIG. 12.14.16... Tandem mill, 18... Wa Applicant's representative Patent attorney Takehiko Suzue 1st M rod 3 figure off 7''-91 = ゛ Figure 4 Procedural amendment Showa 61.3' , -3rd Patent Office Commissioner Michibe Uga1, Indication of the case, Patent Application No. 1988-2709022, Title of the invention ・Method for controlling the thickness of steel materials 3, Person making the amendment Relationship with the case Patent applicant ( 412) Nippon Kokan Co., Ltd. 4, Agent 5, Voluntary amendment -1, + Contents of Meno's amendment 1) Amend the entire specification in attachment 9. 2) Amend Figure 1 of the drawings as a separate matter. Description 1, Title of the invention Method for controlling the thickness of steel material 2, Claims In the method for controlling the thickness of steel material by setting the rolling load of a roll mill, the rigidity value of the roll mill is estimated. Then, the steel material is rolled by setting the rolling load of the roll mill according to the target value of the plate thickness, the actual plate thickness of the rolling mill is measured, and the error between the target value and the actual value of the plate thickness is calculated. A method for controlling the thickness of a steel material, which is characterized in that the mill stiffness value is corrected based on the error value of the plate thickness, and the rolling load of the roll mill is set again using the corrected mill stiffness value. 3. Invention [Industrial Application Field] The present invention relates to a method for controlling the thickness of a steel material by rolling the steel material to a predetermined thickness using a roll mill. [Prior Art] In cold rolling, a steel material is passed through a roll mill. In this case, the roll mill sets the rolling load for the steel material according to the target thickness, but the setting value of this rolling load is determined by the automatic plate thickness connected to the roll mill. Control system (hereinafter referred to as A
GC system). In the AGC system, the screw value is usually calculated based on the plate thickness formula shown in equation (1) below. h = Sr ten f (P, W, DB, Dw, ■) ten δ
-(1) However, h'' target thickness S, It''Lo o-
, st:, /I/ tD 2 creu value, f is P,
A function of W, DB, DW, ■, P is the rolling load, W is the plate width of the rolled material, D! l is the roll diameter of the backup roll, Dw
The roll diameter of the Hower roll, ■ is the rolling speed, and δ is the correction value of the screw value. The method of calculating and controlling the screw value Sr of the roll mill based on equation (1) in this way is generally called the dirgemeter method. In this r-dimeter method, when the variation range of the rolling load P is narrow, the function f is considered to be a line type with respect to P, so
The function f can be expressed by the following equation (2). f=PM(W, DB, Dw, V),
-(2) However, M is mill stiffness. In this equation (2), when the rolling load changes by ΔP,
The control amount ΔS of the screw value of the roll mill is as follows (3)
It is shown by the formula. ΔS = -M・ΔP...(3)
Let the rolling load at an appropriate point after the start of rolling be the reference value P0, the actual measured value P, and the deviation from this Po be ΔP, then Δ
P is calculated by the following equation (4). Δp=p−p, ・・・
(4) Substituting this equation (4) into equation (3), the screw value Δ
The method for calculating Sr is called gauge meter AGC. Furthermore, by directly substituting the measured value P into the equation (1), the following equation (5) can be obtained. The method of determining the screw value S of the roll mill so as to achieve the target plate thickness in equation (5) is called absolute value AGC. S=h−f(P)−δ...(5
) However, the r-dimeter AGC method and the absolute value AGC method
In either method, if an error occurs in the estimated mill stiffness value M with respect to the actual mill stiffness value M, an error ε with respect to the target plate thickness occurs as shown in equation (6) below. In a steady state after a predetermined period of time has elapsed after the start of rolling, the rolling conditions do not change significantly. That is, since the control amount ΔS1 of the screw value is a relatively small amount, the plate thickness error ε with respect to the mill rigidity is relatively small. FIG. 2 shows the relationship between the mill rigidity error and the plate thickness error. In FIG. 2, the horizontal axis represents the plate thickness, and the vertical axis represents the rolling load P. The mill stiffness is determined from the plasticity curve corresponding to the target plate thickness, but since there is an error between the actual mill stiffness M and the estimated mill stiffness M, when this estimated mill stiffness is used, the plate thickness error ε occurs. However, when the roll mill bites the steel material to be rolled, or when the thickness of the steel material is changed during rolling, the rolling conditions vary greatly. Therefore, the control amount ΔS of the screw also becomes large, and as is clear from equation (6), the error in plate thickness based on the error in mill rigidity becomes a considerably large value. for example,
In a cold tandem mill, when the steel material to be rolled is bitten, as the tip of the steel material is bitten by each stand, the tension that the roll mill acts on the steel material in each stand increases from 0 to 10 to 20 kg7. As a result, the rolling load exerted by the mill on the steel material is reduced. In this case, the AGC system changes the screw value by about 0.5 to 1.0 through its automatic control. However, if an error occurs in the mill rigidity, for example, in the case of a 5% error, the plate thickness error ε of the steel material to be rolled is calculated from equation (6), ε=(0,
5-1.0) Expansion X0.05 = 0.025-0.05m. When such a plate thickness error occurs, the quality of the product deteriorates or the product becomes defective, and this defective portion is removed, causing a decrease in product yield. Attempts have been made to improve the accuracy of mill stiffness estimates. For example, the plate thickness control method disclosed in JP-A-60-9512 focuses on the fact that mill rigidity changes depending on the magnitude of rolling load, and calculates the relationship between rolling load and mill rigidity in advance. Then, from this relationship, the mill rigidity according to the value of rolling load is predicted, and this predicted value is used for gauge meter type plate thickness control. [Problems to be solved by the invention] However, the Iron and Steel Institute of Japan, Special Report Livestock 36 (September 1, 1985), "Theory and Practice of Plate Rolling", No. 223
As stated on page. Mill rigidity is influenced not only by the absolute value of the rolling load but also by multiple factors such as the dimensions of the rolls, the material of the rolls, the width of the rolled material, and the rolling speed. Therefore, even if the mill stiffness is predicted or compensated for only a single factor such as the rolling load, the mill stiffness cannot be accurately predicted or compensated for, and there is a problem that the plate thickness accuracy decreases. This invention was made in view of such circumstances, and an object of the present invention is to provide a method for controlling the thickness of a steel material that can obtain a highly accurate thickness. [Means for Solving the Invention] A method for controlling the thickness of a steel material according to the present invention is a method for controlling the thickness of a steel material by setting a rolling load of a roll mill. Then, set the rolling load of the roll mill according to the target value of plate thickness, roll the steel material, actually measure the plate thickness after rolling, calculate the error between the target value of plate thickness and the actual value, and calculate this plate thickness. The roll mill stiffness value is corrected based on the error value, and the roll mill rolling load is set again using the corrected mill stiffness value. In the steel plate thickness control method according to the present invention, when rolling is started, the tension of the steel material acts on the roll mill. That is, the tension of the steel material acts on the roll mill at the same time as the biting occurs from the tensionless state before rolling. Due to such a change in tension, the mill rigidity M as a rolling condition of the roll mill changes. That is, since an error occurs in the mill stiffness value, it is necessary to correct the screw value S. In this case, the correction amount (change f) of the screw value Sr is ΔS. Then, the correction amount ΔS can be obtained by the following equation (7). Here, Δh is the amount of change when changing the thickness of the plate to be rolled during rolling. Therefore, at the time of biting, Δh is 0. ΔP is the amount of change in rolling load, and M is the estimated mill rigidity value. On the other hand, the following equation (8) can be obtained from equation (6). However, there is a time lag between the amount of change ΔS in the screw value and the actual value of the plate thickness after rolling because the plate thickness measurement detector is installed on the exit side of the tandem mill. Such a time shift is shown in FIG. In FIG. 3, the horizontal axis shows time, and the vertical axis shows the amount of change ΔS in screw value and the amount of change in plate thickness. As is clear from FIG. 3, the amount of change in screw value affects the change in plate thickness after time Δ has elapsed. Therefore, in order to correct such a time difference, the time when the plate thickness after rolling is actually measured is t, the time difference between the time during rolling and the time when the plate thickness is measured is Δt, and the circumferential speed of the roll is If V is the distance between the roll mill and the plate thickness detector, t is the distance between the roll mill and the plate thickness detector, then the following equation (9) can be obtained from the above equation (8). In this case, it can be determined by Δt=t/V. That is, the actual mill stiffness value M can be obtained from the following equation by modifying equation (9). Using this aQ equation, the actual mill stiffness value M is calculated from the estimated mill stiffness value M and the plate thickness error value e, and this actual mill stiffness value is used in the above-mentioned equation (1) to calculate the screw value ΔSr again. and set. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4 of the accompanying drawings. As shown in FIG. 1, tandem mills 12, 14, and 16 are installed along the sheet passing direction in the cold rolling line 1o. Each tandem mill 12゜14.16 has a pair of work rolls (roll mill) 1 that press the steel material from above and below.
8 are provided, and each work roll 18 is connected to a backup roll 19 that applies a rolling force. Each tandem mill 12, 14. 161t'L are each connected to a control unit 20 that sets the roll opening degree (gap between rolls) of the work rolls 18. Although this control unit 2o is connected to each tandem mill 12, 14, 16, only the control unit 20 of the tandem mill 12 will be described in FIG. 1 because they are substantially the same. The control unit 20 includes a hydraulic reduction device 22 that applies a reduction force to the work rolls 18 via a backup roll 19 in order to set the roll opening degree between the pair of work rolls 18, and a hydraulic reduction device #, 22VC. A roll opening degree detector 24 is provided to detect the roll opening degree. The hydraulic lowering device 22 and the roll opening degree detector 24 are each AG
C (automatic plate pressure control) device 26, and the roll opening degree detector 24 is further connected to a mill rigidity learning system 27. The AGC device 26 calculates based on the detected value from a predetermined detector, and controls the drive of the hydraulic pressure lowering device 22 according to this calculated value. On the other hand, the mill stiffness learning system 27 is connected to the AGC device 26, calculates the mill stiffness error based on the detected value from a predetermined detector, and sends this error value to the AGC device as a data signal. The work roll 18 is provided with a rolling load detector 28 that detects the rolling load applied to the work roll 18 by the hydraulic rolling device 22. This work roll 18 is connected to an AGC device 26,
A detection signal is sent to the GC device. A rotation speed detector 30 for detecting the rotation speed of the work roll 18 is further attached to the work roll 18 . This rotation speed detector 30 is connected to the mill stiffness learning system 27 and sends a detection signal to the mill stiffness learning system. A plate thickness detector 32 is provided on the exit side of the work roll 18 to measure the thickness of the steel material rolled by the work roll 18. This plate thickness detector 34 is connected to the mill stiffness learning system 27 and the AGC device 26, and sends detection signals to each. A tension detector 34 is installed adjacent to the plate thickness detector 32 to measure the tension of the rolled steel material. This tension detector 34 is connected to the AGC device 26 and
A detection signal is sent to the C device 26. Next, the operation of this embodiment will be explained. When the steel material is conveyed to the cold rolling line 10, the tandem mill 12 uses a hydraulic rolling device 2 to roll the steel material to a target thickness.
2 to apply a predetermined rolling force to the work roll 18. In this case, the AGC device 26 calculates the rolling load based on the above-mentioned equation (1). That is, the target plate thickness is determined using the formula (1), and the rolling load P, the plate width W of the rolled material, the roll diameter DB s of the backup roll 19, the work roll 1
By substituting the values of the roll diameter and rolling speed V of No. 8, the screw value sr of the roll mill is calculated. Note that the function f is calculated from equation (2), but in this case,
As the mill stiffness value M of the work roll, an estimated value estimated from the material of the work roll is used. In this way, the AGC device 26 uses the estimated mill stiffness value M of the work roll to calculate the screw value Sr according to the target plate thickness. Then, the AGC device 26 controls the oil positive pressure reduction device 22 to the obtained screw value S. Next, the steel material is bitten by the work rolls 18 and rolling is started. In this case, the roll opening degree detector 24 measures the gap between the work rolls 18 and sends the measured value to the AG
C device 26 and mill stiffness learning system 27. Furthermore, the rolling load detector 28 sends the measured value to the AGC device fIt26.
send to The roll rotation speed detector 30 sends its measurements to the mill learning system 27 . The steel material rolled by the work rolls then moves to a plate thickness detector 32. The plate thickness detector 32 measures the plate thickness of the steel material after rolling, and sends the measured value to the AGC equipment fl 126 and the mill rigidity learning system 27. The mill tonality learning system 27 calculates the actual mill stiffness value M by correcting the estimated mill stiffness value based on the above-mentioned formula 01. That is, the error ε between the plate thickness after rolling and the target plate thickness,
Modify the mill stiffness value from the amount of change in screw value. This corrected mill stiffness value is sent to the AGC device 26. The AGC device 26 converts this corrected mill stiffness value into the above-mentioned (
1) Calculate the screw value Sr for Shinko using the formula. A
The GC device 26 issues a control signal to the hydraulic pressure reduction device 22 to reset to a new screw value S. The hydraulic rolling device fIt22 is reset and applies a new rolling blade to the work roll 18 via the backup roll 19. This new rolling blade continues to roll the steel material and then winds it into a coil. Since the rolled steel material is rolled using the estimated mill rigidity at the start of rolling, off-gauge occurs at the tip. When the off-dage length of the tip of the coil was measured, the results shown in FIG. 4 were obtained. FIG. 4 shows the offage length on the horizontal axis and the frequency on the vertical axis, and shows the case where a steel material is rolled in a tandem mill having five cold rolling mills. The solid line in FIG. 4 shows the present invention, and the broken line shows the conventional method. As is clear from FIG. 4, the conventional offage length was about 10 m on average, but according to the present invention, it can be shortened to about 3 m on average. This invention is not limited to the one embodiment described above, and can be modified in various ways without departing from the gist of the invention. For example, the present invention is not limited to resetting the crushing load of the roll mill at the start of rolling the steel material, but may also be used to change the target thickness of the steel material during rolling. [Effects of the Invention] According to this invention, the roll mill rigidity value can be corrected simply by measuring the plate thickness of the steel material after rolling, and the rolling load of the roll mill is set again using the corrected mill rigidity value. , it is possible to obtain steel materials with high precision plate thickness. 4. Brief description of the drawings Fig. 1 is a schematic diagram of a cold rolling mill according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between mill rigidity error and plate thickness error, and Fig. 3 4 is a graph showing the time delay between the change in screw value and the change in plate thickness, and FIG. 4 is a graph showing the offage length of the tip of the coil rolled according to the present invention in comparison with the conventional one. . 12.14.16... Tandem mill, 18... Work roll, 22... Hydraulic reduction device, 26... AG
C device, 27... Mil stiffness learning system, 32...
Plate thickness detector. Applicant's agent Patent attorney Takehiko Suzue fjs1 Figure

Claims (1)

[Claims] In the steel plate thickness control method that controls the plate thickness of steel by setting the rolling load of the roll mill, the stiffness value of the roll mill is estimated, and the rolling load of the roll mill is set according to the target value of plate thickness to roll the steel plate. , actually measure the plate thickness after rolling, calculate the error between the target plate thickness value and the actual measured value, correct the mill stiffness value based on this plate thickness error value, and use the corrected mill stiffness value. A method for controlling the thickness of a steel material, characterized by setting the rolling load of a roll mill again.