JPH0780524A - Method for controlling plate thickness in plate rolling - Google Patents

Abstract

PURPOSE:To provide a method for automatically controlling plate thickness in a plate rolling, by which method a rolled plate excellent in the plate thickness accuracy is stably manufactured. CONSTITUTION:Reference is made to a plate rolling, in which a rolling mill is used that is provided with a roll space changing device 7 capable of arbitrarily changing the space S between an upper and lower rolling rolls 1 and with a deviation detector 4 for the plate thickness on the entrance side, and in which the plate thickness is controlled by adjusting the roll space while the deviation is measured of the thickness on the entrance side. A rolling reaction force which is imparted to the upper and lower rolls 1 in the middle of rolling is estimated by calculation. Then, the plate thickness value on the entrance side of the rolling mill, which is made the calculation element of this rolling reaction force, is obtained by an arithmetic unit 8, making a reference thickness value for the plate thickness deviation detector 4 on the entrance side of the rolling mill, and the controlling quantity is calculated of the space between the upper and lower rolls in the middle of rolling based on the output of this plate thickness detector 4, which quantity is then inputted in a device 8 for controlling the roll space so as to control the thickness of the plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic plate thickness control method in plate rolling capable of stably producing a rolled plate having excellent plate thickness accuracy.

[0002]

2. Description of the Related Art As shown in FIG. 3, when a plate material (steel plate or the like) is rolled between upper and lower rolling rolls (work roll 1, backup roll 2) of a rolling mill. However, the strip thickness on the delivery side of the rolling mill tends to vary due to the "thickness variation on the rolling mill entry side" or "uneven hardness in the rolling direction" of the material 3 to be rolled, and therefore a highly accurate rolling strip should be provided. In order to obtain it, it is necessary to accurately control the interval between the upper and lower rolling rolls.

Therefore, conventionally, in order to prevent the strip thickness on the delivery side of the rolling mill from deviating from the target value, the inlet strip thickness deviation detector 4 or the outlet strip thickness deviation detector 5 arranged before and after the rolling mill, or the rolling strip. -A rolling reaction force measuring device (load cell) 6 installed in the roll measures the thickness deviation on the inlet side or the outlet side of the rolling mill or the rolling reaction force (load) applied to the vertical rolling roll during rolling. However, automatic gauge control (AGC: Automatic Gauge Control) for controlling the interval between the upper and lower rolling rolls has been performed.

In the method of controlling the interval between the upper and lower rolling rolls by using the deviation output of the strip thickness deviation detector on the rolling mill exit side, the reference value set in the strip thickness deviation detector on the rolling mill exit side is It is a target value for the thickness of the material to be rolled, and the target thickness can be obtained by controlling the interval between the upper and lower rolling rolls of the rolling mill in proportion to the deviation output from the thickness deviation detector (monitor AGC). I am trying.

On the other hand, the control of the interval between the upper and lower rolling rolls using the deviation output of the strip thickness deviation detector on the inlet side of the rolling mill predicts the sheet thickness variation on the outlet side on the basis of the sheet thickness variation on the inlet side. However, it is intended to suppress the variation of the plate thickness on the output side based on this predicted result.For example, when the plate thickness on the input side is larger than the reference value, the interval between the upper and lower rolls should be adjusted to be slightly smaller in advance. Is a method for making the outgoing side plate thickness match the target plate thickness {Feed Forward AGC (hereinafter referred to as "FF-AGC")}.

Further, as a method of controlling the roll interval in accordance with the rolling reaction force (load) applied to the upper and lower rolls during rolling, a certain time (extremely short biting time) from the start of rolling is used. Rolling reaction force (load) P ^* (called "lock-on load") at the start of control (= lock-on) after passing is used as a reference, while measuring rolling reaction force (load) P during rolling, "P-
P ^* "is calculated and the interval between the upper and lower rolls is changed by an amount proportional to this value to control so as to prevent the deviation of the plate thickness in the rolling direction (hereinafter referred to as" BISRA-AG
C ”), the rolling reaction force generated when rolling down to the target thickness is estimated in advance (this estimated value is P ₀ ), and the rolling reaction force (load) P during rolling is measured. A method of calculating the difference "P-P ₀ " from the estimated value and changing the interval between the upper and lower rolls by an amount proportional to this value so as to obtain a target plate thickness (absolute value AGC (Hereinafter "ABS-
AGC ″)).

However, each AGC has advantages and disadvantages,
Therefore, for example, in the case of a thick steel plate to which the reversal rolling is applied, the type of AGC to be applied is properly used depending on the stage of the rolling pass.

Here, the advantages and disadvantages of each AGC will be summarized. For example, in the monitor AGC, the interval between the upper and lower rolling rolls is controlled so that the target thickness is obtained while measuring the plate thickness itself of the material to be rolled. Although the target strip thickness can be obtained irrespective of the model error, control delay occurs because the rolling roll interval is controlled by feeding back the strip thickness deviation on the delivery side of the rolling mill and rolling. If there is a sudden change in thickness or hardness of the material to be rolled before entering the machine, it cannot be sufficiently dealt with, resulting in a problem that the product sheet thickness accuracy deteriorates.

On the other hand, in the FF-AGC, since the rolling roll interval is controlled based on the sheet thickness deviation on the rolling mill entrance side, the thickness variation of the material before rolling can be accurately controlled. Although it is very advantageous as compared with the above monitor AGC, it is difficult to deal with uneven hardness of the material to be rolled in the rolling direction, and therefore, it cannot be said that the plate thickness accuracy is sufficient. .

On the other hand, BISRA-AGC is very effective in suppressing the plate thickness deviation in one plate, but as a result, the plate thickness immediately after biting (the plate thickness at the start of control and the target plate (The thickness often does not match the thickness) is used as a reference, and the total length thickness is controlled to this value.Therefore, there are setup errors due to rolling load prediction errors, etc. When the thickness error is positive (a value that is slightly thicker than the target plate thickness), there is a problem that a positive plate thickness error is generated as it is.

ABS-AGC is made of a material, a reduction ratio,
The rolling reaction force is estimated in advance based on the rolling temperature, etc., and the gap between the upper and lower rolls is controlled based on this and the actual rolling reaction force (load). Irrespective of its excellent effect of suppressing both "thickness deviation within one sheet" and "thickness error from target sheet thickness" and there is no problem like BISRA-AGC,
Occasionally, errors in estimation of elongation of the rolling mill, flattening of rolls, deflection, etc., caused by rolling reaction force (load), directly cause errors in plate thickness, so that it may not be possible to obtain sufficiently stable results.

Thus, the AGCs proposed so far
The advantages and disadvantages of each were pointed out, and they were used accordingly, but in recent years, even more stringent demands for improving the thickness accuracy of rolled products have been extended to thick steel plates, etc. There was an urgent need to develop a means for controlling the plate thickness.

Therefore, rather than applying the conventional AGC individually, the advantages of each AGC can be combined and taken out.
Attempts have been made to combine a plurality of AGCs in an attempt to realize GC, but with a simple combination, the effects of each other interfere with each other and have the opposite effect, and it has been extremely difficult to obtain favorable results.

However, in JP-A-56-141906, BISRA-AGC and monitor AGC are used together.
As a method to achieve the target plate thickness by combining them, the lock-on load described above is corrected by the monitor feedback signal when the plate thickness deviation on the delivery side of the rolling mill deviates from the allowable thickness range, and the rolling mill control system A method of adjusting the tuning rate has been proposed. However, even this method has not solved the problem that sufficient measures cannot be taken when the inlet plate thickness varies or when the control length in the rolling direction is short.

Further, in Japanese Patent Laid-Open No. 63-309315, in order to use and combine BISRA-AGC and FF-AGC together, the strip thickness of the material to be rolled into the rolling mill is continuously measured just before the rolling mill. Of the rolling thickness in the current pass is predicted from the sheet thickness deviation, and the gap between the upper and lower rolling rolls is calculated from the predicted rolling load variation and the lock-on load. The method of rolling while correcting the moment is proposed. However, this method also has a problem that the plate thickness cannot be accurately controlled when the lock-on load measured immediately after the start of rolling becomes the load in the load unstable region immediately after biting. It was

From the above, the object of the present invention is to solve the above problems pointed out in the conventional plate thickness control method used for plate rolling, and to obtain a rolled plate with high plate thickness accuracy in a stable manner. Was placed in establishing an automatic plate thickness control means.

[0016]

The present invention has been made in order to achieve the above-mentioned object, and is provided with "a rolling-down device capable of arbitrarily changing the interval between the upper and lower rolling rolls and a plate thickness deviation detector. Using a rolling mill, the rolling width of the strip is controlled by adjusting the roll interval while controlling the strip thickness deviation on the rolling mill entrance side. The rolling reaction force applied to the rolling roll is estimated, and the strip thickness value on the rolling mill entrance side, which is a factor for calculating this rolling reaction force, is calculated and the reference strip thickness for the strip thickness deviation detector on the rolling mill entry side is calculated. Value, and by calculating and controlling the control amount of the vertical rolling roll interval during rolling based on the output of this plate thickness deviation detector, it is possible to achieve the target plate thickness with high accuracy. It has features.

As described above, the present invention is, so to speak, "a method of controlling the interval between the rolls according to the rolling reaction force applied to the upper and lower rolls during rolling (BISRA-AGC or ABS-AG.
C) and FF-AGC are combined to try to enjoy their respective advantages. BISRA-AGC and FF-A
When using in combination with GC or ABS-AGC and FF-AGC, "Select the appropriate reference strip thickness to be set in the strip thickness deviation detector on the rolling mill entrance side" and "Upper and lower rolling rolls during rolling" -By appropriately selecting the target value given to the control system of the gap distance, it is possible to eliminate the above-mentioned adverse effects and to stably manufacture a rolled plate with excellent plate thickness accuracy.
Hereinafter, the present invention will be described more specifically.

FIG. 1 is a schematic diagram for explaining a main part of a sheet rolling facility for carrying out the method of the present invention, and FIG. 2 is a control block diagram thereof. In FIG. 1, the material to be rolled 3 is rolled between the upper and lower rolling rolls (work roll 1 and backup roll 2) of the rolling mill to have a predetermined thickness (target thickness). The deviation of the sheet thickness before rolling is continuously detected by the sheet thickness deviation detector 4 provided on the inlet side of the rolling mill.

Here, the inventor of the present invention said that "the reference thickness for measuring the deviation of the sheet thickness before rolling" is "the rolling reaction force applied to the upper and lower rolling rolls during rolling when the target thickness is to be obtained. (BISR
It is the rolling reaction force during rolling in A-AGC or ABS-AGC, and is calculated using BISRA-AGC or ABS-AGC as the factors such as the inlet side plate thickness when performing "). It is found that it is possible to control the plate thickness extremely accurately when the reference value and the target plate thickness in the front pass or the front stand are in agreement, but this is the idea that forms the basis of the present invention. ing.

This is for the following reason. That is, generally, the plate thickness h on the delivery side of the rolling mill is the load required to increase the unit length of the opening S of the vertical rolling roll, the roll reaction force P during rolling, and the opening of the vertical rolling roll. Using M (mill stiffness coefficient), it can be calculated by h = S + P / M (1). Therefore, the set opening S of the rolling roll S
_{If the} rolling reaction force (load) estimated to occur during rolling is P ₀ and the target plate thickness is h _aim , the _set is determined as S _set = h _aim − P ₀ / M …… (2) It will be good if you do.

The rolling reaction force P ₀ is calculated by the following equation. P ₀ = K _fm × l _r × W × Q _p However, K _fm : Restraint deformation resistance, l _r : Contact arc length, W: Rolled material strip width, Q _p : Rolling force function. Here, Q _p is the material temperature and the reduction amount (= [sheet thickness before rolling] −
[Target thickness]), etc.

The present invention is characterized in that "the target plate thickness when rolling by the front pass or the front stand" is used as the entrance side plate thickness when the rolling reaction force P ₀ is obtained. this is,
This is because the FF-AGC that processes the “error caused by rolling in the previous pass or the previous stand” as the “incoming-side thickness variation component” is applied to eliminate the output-side thickness error.

The sheet thickness deviation in FF-AGC is a deviation from "the target sheet thickness in the rolling in the preceding pass or the preceding stand", but here, for example, when BISRA-AGC is used together, The target plate thickness can be obtained with high accuracy by the method of the present invention described below.

That is, ABS-AGC or BISRA-A
When both GC and FF-AGC are used together, the difference between the rolling load P _O and the actual load during rolling ΔP, the difference between the plate thickness of the rolled material and the plate thickness of the rolled material used when estimating P _O ΔH, ABS
-Assuming that the gain of AGC or BISRA-AGC is K _A , the control formula of the correction amount ΔS from the setup amount of the vertical rolling roll interval during rolling is ΔS = -K _A × ΔP / M- (1-K _A ) × ΔH × QH / M (3) However, QH = ∂P / ∂H. In addition, "QH = ∂P / ∂H" represents "the fluctuation of the rolling reaction force according to the fluctuation of the entrance side plate thickness".

When the ABS-AGC and the FF-AGC are used together, the plate thickness can be accurately controlled by this method for the following reasons. In other words, when the input side reference plate thickness used when calculating the load P ₀ that is the reference value of ΔP in the equation (3) does not match the reference plate thickness set in the input side plate thickness deviation detector. , And the difference is Δh,
The second term shown in the equation (3) is (1-K _A ) × (ΔH + Δh) × QH / M, so that “− (Δh × QH / M)” is the control amount Δ.
This is because it becomes an error of S.

On the other hand, BISRA-AGC and FF-AGC
When both and are used together, the plate thickness can be accurately controlled by this method for the following reasons. That is, if the deformation resistance of the material is K, and the rolling reaction force fluctuation amount, the deformation resistance fluctuation amount, and the inlet side plate thickness fluctuation amount based on the BISRA-AGC lock-on load are ΔP ′, ΔK ′, and ΔH ′, respectively, ΔP ′ It is widely known that = (∂P / ∂K) × ΔK ′ + (∂P / ∂H) × ΔH ′ (4) holds. In the above equation (4), the first term “(∂P / ∂K) × ΔK ′” represents the rolling reaction force variation due to the variation of the deformation resistance, and the second term “(∂P / ∂H ) × ΔH ′ ”represents the fluctuation of the rolling reaction force due to the fluctuation of the inlet plate thickness.

Therefore, the control formula for the control amount ΔS of the interval between the upper and lower rolling rolls after the BISRA-AGC lock-on is:
The formula obtained by substituting Eq. (4) into Eq. (3), that is, However, E = K _A × {(∂P / ∂H) / M} × (ΔH−ΔH ′) (6)

In the above control equation (5), the term E is a control disturbance. Therefore, in order to perform stable control in BISRA-AGC, it is necessary to remove this disturbance component E. Then, in order to remove this disturbance component E,
From equation (6), it is clear that “ΔH = ΔH ′” should be satisfied during the control of BISRA-AGC. Therefore, the reference strip thickness value for the strip thickness deviation detector disposed on the rolling mill entry side is made to match the entry side strip thickness calculated value at the time of BISRA-AGC lock-on, and rolling is performed according to the output of this strip thickness deviation detector. By adjusting the control amount of the interval between the upper and lower rolling rolls, it is possible to use BISRA-AGC and FF-AGC together to accurately obtain the target plate thickness.

Therefore, in FIG. 1, the reference plate thickness value set in the plate thickness deviation detector 4 is "BISR" calculated based on the measured value of the rolling reaction force measuring device (load cell) 8.
A-AGC lock-on input side plate thickness calculated value ".
Then, based on the plate thickness deviation detection output from the plate thickness deviation detector 4 for which such a reference plate thickness value is set, the calculator 9 calculates the vertical rolling roll interval control amount, and the roll interval control is performed. When the opening degree of the vertical rolling roll is adjusted through the device (AGC controller) 8 and the roll gap changing device 7, proper plate thickness control can be stably performed.

By the way, in actual control, BIS
Estimating the sheet thickness from the output of the sheet thickness deviation meter at the time of RA-AGC lock-on and changing the reference sheet thickness of the sheet thickness deviation detector has a problem that it takes time to change the setting. Therefore, as a practical method, the reference strip thickness set before the start of rolling is set to the entry strip thickness (= the target strip thickness in the previous pass or the stand) used when estimating the rolling load P _0, and Records the calculated plate thickness at the time of lock-on, and subtracts this from the reference plate thickness of the plate thickness deviation detector to obtain the output of the plate thickness deviation detector, so that BISRA-AGC and FF-A
The target plate thickness can be obtained without error even when using GC together.

[0031]

Example: Length is 4000 to 5000 mm, width is 2000
Prepare a slab (steel slab) with a thickness of up to 3000 mm and a thickness of 100 mm, and use the rolling equipment shown in FIGS. 1 and 2.
Sheet rolling according to the method of the present invention and sheet rolling according to the comparative method were performed. In each case, the target plate thickness was set to 12 to 15 mm, and rolling was performed on 100 slabs.

Here, a γ-ray thickness gauge was applied as the plate thickness deviation detector, and the plate thickness at the steel plate center portion was measured. A load cell attached to the upper part of the rolling mill was applied to detect the "rolling reaction force" when the method of the present invention was carried out, and a magnetic length measuring machine was used to detect the roll interval.

In the present embodiment, "control I (FF + BISRA) according to the method of the present invention" and "control II according to the method of the present invention"
(FF + ABS) "," Control I by comparative method "and" Control II by comparative method "were carried out, and the procedure will be described below.

A) Control I by the method of the present invention The slab described above was rolled by reversal rolling for 1 to 15 passes. In addition, the plate thickness detector is installed only on the rolling mill entrance side,
The rolling direction from the first pass at the beginning of rolling was determined so that FF-AGC could be used in the final pass. That is, in the final pass, rolling is performed from the entrance side plate thickness deviation detector 4 side shown in FIG. 1 (passes in this direction are defined as forward rotation passes and reverse paths are defined as reverse rotation passes), and rolling is performed. did. For the passes other than the final pass, the rolling directions were determined so that the rolling direction in the final pass would be the forward pass and the forward and reverse passes would alternate. AGC is FF-AGC in the forward rotation path.
And ABS-AGC are used together, and since the thickness deviation detector cannot be installed on the rear surface of the rolling mill, ABS-AGC is used in the reverse pass.
Used only. b) Control II according to the method of the present invention Tests were carried out in the same manner as "Control I according to the present invention" described above, except that BISRA-AGC was used instead of ABS-AGC. c) Control I by the comparative method In "Control I by the method of the present invention", BISRA-AG
Plate thickness control is performed without changing the plate thickness detector output when C lock is on. c) Control by comparative method II Plate thickness control is performed only by FF-AGC.

Then, the plate thickness deviation of the plate material obtained by rolling applying each of the above methods was investigated, and the results are shown in Table 1. As is clear from the results shown in Table 1,
It can be seen that according to the method of the present invention, it is possible to obtain a highly accurate rolled steel sheet with a very small thickness deviation.

[0036]

[Table 1]

[0037]

[Summary of Effects] As described above, according to the present invention, industrially useful effects such as the ability to easily and stably provide a rolled plate having a high plate thickness accuracy are provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a main part of a strip rolling facility for carrying out the method of the present invention.

FIG. 2 is a control block diagram for carrying out the method of the present invention.

FIG. 3 is an explanatory diagram of an outline of rolling equipment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 work roll 2 backup roll 3 material to be rolled 4 inlet side plate thickness deviation detector 5 output side plate thickness deviation detector 6 rolling reaction force measuring device 7 roll interval changing device 8 roll interval control device ( AGC controller) 9 Roll interval, rolling reaction force, reference thickness calculator

Claims (1)

[Claims] 1. A rolling mill equipped with a reduction device capable of arbitrarily changing the interval between the upper and lower rolling rolls and a plate thickness deviation detector,
In the rolling of a plate material in which the plate thickness is controlled by adjusting the roll interval while measuring the plate thickness deviation on the entrance side of the rolling mill, it is added to the upper and lower rolling rolls during rolling to obtain the target thickness. The rolling reaction force is estimated by calculation, and the plate thickness value on the rolling mill entrance side, which is the factor for calculating this rolling reaction force, is calculated and used as the reference plate thickness value for the rolling mill entrance side plate thickness deviation detector. Based on the output of the deviation detector,
A method for controlling plate thickness, which comprises calculating and controlling a control amount of the gap.