JP3016119B2 - Thickness control method of taper plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for rolling a so-called tapered plate in which the thickness of a material to be rolled changes from one end in the longitudinal direction to the other end using a conventional rolling machine for steel plates (flat plates). The present invention relates to a sheet thickness control method.

[0002]

2. Description of the Related Art Normally, thickness control in flat rolling is performed by a basic relationship represented by the following equation (1), which is established between a rolling load P, a roll gap S of a rolling roll, and an outlet thickness h of a rolling mill. It is performed based on. h = S + (P / M) (1) where M is the mill stiffness coefficient. Hereinafter, the same symbols are used with the same meaning.
You.

The equation (1) is always satisfied in the rolling state. However, in the prediction calculation before the material to be rolled is engaged, in order to obtain the target exit side sheet thickness h ₀ , the same equation (1) is used. The roll gap S ₀ is set based on the predicted rolling load P ₀ using the equation (2). h ₀ = S ₀ + (P ₀ / M) (2) Hereafter, the same symbols are used in the same meaning.
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[0004] Then, the exit side plate thickness h obtained by the equation (1).
And (2) setting the roll gap S system <br/> control in accordance with the following equation (3) to match the target delivery side thickness h ₀ obtained by the formula. S = S ₀ − (1 / M) · (P−P ₀ ) (3)

The equation (3) is a control method generally called "absolute value AGC", which is widely used for controlling the thickness of flat plate rolling. For example, in Japanese Patent Application Laid-Open No. 51-97565, a roll gap for changing the target outlet side plate thickness every moment according to the pressure extension based on the above equation (3).
A method has been proposed in which the loop S is given by equation (4).

S = S ₀ − (1 / M) · (P−P ₀ ) + Δh _T (4) where Δh _T : target outlet taper thickness change corresponding to pressure extension based on the biting end Quantity (the same sign has the same meaning hereafter)
Further , in Japanese Patent Application No. 6-225439, in order to prevent the control system from becoming unstable due to the influence of mill hysteresis, the scale factor K which is the gain of the thickness control system in the absolute value AGC is used. Change the target exit side taper thickness so that the target taper thickness can be obtained even when _A is used.
A method for correcting the quantity Δh _T to η · Δh _T is disclosed.

[0007] By setting the roll gap in accordance with the following equation (5) in this technique, even if the scale factor K _A is the gain of the gauge control system is less than 1.0, exit target thickness at delivery side of the side tapered plate It is designed to match the thickness.

[0008]

(Equation 1)

[0009]

In the prior art described above, the plasticity factor Q for obtaining the exit side thickness target value gain η given by equation (6) is determined in advance for a plurality of points in the longitudinal direction of the material to be rolled. It is required to change this moment by moment according to the extension of the pressure, thereby coping with the variation in the plasticity coefficient in the longitudinal direction. However, such a conventional method has a problem that the influence of the fluctuation of the plastic coefficient cannot be completely eliminated.

The present inventors have conducted studies to eliminate the influence of the fluctuation of the plastic coefficient in the prior art, and have obtained the following findings. That is, one of them is the aforementioned (5), (6)
The sheet thickness control method based on the equation predicts a rolling load fluctuation amount when rolling a tapered plate, and can be regarded as a sheet thickness control based on the predicted value. From this perspective, (5),
The following equation (7) can be derived from the equation (6).

[0011]

(Equation 2)

The predicted rolling load variation ΔP in the equation (7) is
ΔP = −Q · Δh _T , but when the load fluctuation prediction by this equation is correct, in other words, when ΔP = (P−P ₀ ), this relationship can be substituted into equation (7). ,
Equation (8) is obtained.

[0013]

(Equation 3)

The equation (8) is equivalent to the equation (4) when the absolute value AGC is performed with the scale factor K _A , which is the gain of the sheet thickness control system, set to 1.0, that is, the equation (4). It becomes equal to the side taper plate thickness (h ₀ + Δh _T ). However, if the relationship of ΔP = P-P ₀ is not established, when there is an error in the load change predicting wife <br/> Ri ΔP = -Q · Δh _T is a problem that an error in the thickness at delivery side occurs is is there. Another one
One is the definition of the plasticity factor Q of the material to be rolled (Q = -∂P / ∂h)
Therefore, the expression ΔP = −Q · Δh _T holds only when Δh _T is very small.

Therefore, even if the distribution of the plasticity factor Q of the material to be rolled in the longitudinal direction is calculated in advance, if Δh _T increases, the above equations (7) and (8) do not hold, and the exit side sheet thickness becomes the target taper. It will deviate from the plate thickness. The present invention has been made based on such knowledge, and the purpose thereof is to provide a case where the thickness difference between the thin end and the thick end is large, and the plastic coefficient change in the longitudinal direction of the material to be rolled is large, To provide a taper plate thickness control method that can obtain a taper plate having an intended gradient even when the scale factor of the absolute value AGC is set to a value smaller than 1.0 for control stability. is there.

[0016]

Means for Solving the Problems] gauge control method of the taper plate according to the present invention, the relationship between b Rugyappu the rolling load at the time of flat rolling, and a control system for performing plate thickness control based on the predicted rolling force Using, in the thickness control method of the taper plate to continuously change the outlet thickness in the rolling direction by changing the target outlet thickness to taper according to the pressure extension, the longitudinal distribution of the plastic coefficient of the material to be rolled and Target exit side plate
The rolling gap change amount is calculated from the thickness and the roll gap is corrected based on the mill stiffness coefficient and the gain of the plate thickness control system.

[0017]

In the the present invention, as the target delivery side thickness <br/> thereby, using the target output side tapered thickness values, the predicted rolling load variation amount for obtaining this target output side tapered thickness value Along with obtaining the tapered plate thickness target value and the plastic coefficient distribution in the longitudinal direction of the material to be rolled, by correcting this based on the mill stiffness coefficient and the gain of the plate thickness control system, in the longitudinal direction of the material to be rolled. Even when the change in the plastic coefficient is large, or when the scale factor, which is the gain of the thickness control system, is set to a value smaller than 1.0, a tapered plate having an accurate gradient can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a control system for implementing a method for controlling the thickness of a tapered plate according to the present invention. In FIG. 1, reference numeral 1 denotes a rolling mill, 2 denotes a pressing device having a hydraulic cylinder, and 3 denotes a pressing position detection. , 4 is a rolling load detector,
Reference numeral 5 denotes a pulse generator that outputs a pulse according to the number of rotations of the work roll 1a, and reference numeral 6 denotes a material to be rolled. Rolling mill 1
Is provided with a work roll 1a and a backup roll 1b, through which the material 6 to be rolled is inserted a plurality of times from the direction of the arrow in the same direction or alternately in the opposite direction to be rolled. The rolling position is detected by the rolling reduction position detector 3, the rolling load is detected by the rolling load detector 4, and the rolling speed is detected by the pulse generator 5,
The roll gap is adjusted by the rolling-down device 2 based on these detection results.

11 is a setting device for setting a target exit side tapered plate thickness Δh (thickness difference between a thin end and a thick end of the rolled material 6 at the exit side of the rolling mill 1) with respect to the rolled material 6; Numeral 12 sets a roll gap S ₀ at the time of mill biting, a predicted rolling load P ₀ , a mill stiffness coefficient M, a scale factor K _A which is a gain of a plate thickness control system, a plastic coefficient Q _{i at a} point i of the material to be rolled, and the like. It is a constant setting device for Setting device 11
Is set to the target taper thickness change amount setting unit 13. The target taper thickness change amount setting unit 13 is provided with the input target exit side taper thickness Δh and the number of pulses taken in from the pulse generator 5, in other words, the pressure extension of the material 6 to be rolled (distance mm from the biting end). And the target exit side of each part in the longitudinal direction according to the following equation (9).
The change amount of the taper plate thickness (the target change amount of the taper thickness at the outlet side at the point i, Δh _T ) is calculated, and the calculated change amount is given to the rolling load fluctuation estimator 14 and the target roll gap setting device 15. Δh _T = Δh _n · i (9) where Δh _n : a value obtained by equally dividing Δh by n

FIG. 2 is an explanatory diagram showing the relationship between the target exit side taper plate thickness Δh and the target exit side taper plate thickness variation Δh _{T of} each portion in the longitudinal direction. In FIG. 2, the horizontal axis shows the distance from the thin end to the thick end of the material 6 to be rolled on the exit side of the rolling mill, and the vertical axis shows the thickness difference between the thin end and the thick end. The material to be rolled 6 is divided into n equal parts in the rolling direction which is the longitudinal direction, in other words, the target exit side tapered plate thickness Δh is divided into n equal parts, and the value is given by Δh _n
Then, starting from the thin end of the material 6 to be rolled,
The target tapered thickness change amount Δh _{T at the} i-th point is expressed by the above equation (9).

The rolling load variation estimator 14 calculates the target taper thickness change Δh _{T of} each portion in the longitudinal direction of the material 6 to be rolled inputted from the target taper thickness change amount setter 13 and the constant setter 12. Based on the set plasticity coefficient Q _{i of the} material to be rolled at the time of the i-point rolling, a rolling load fluctuation predicted value ΔP _i as shown in the following equation (10) is calculated, and the calculated rolling load fluctuation value ΔP _i is provided to the target roll gap setting device 15. ΔP _i = −Σ (Q _i · Δh _n ) (10) where i = 1 to n (indicating the i-th position from the biting end when the longitudinal direction of the material to be rolled is equally divided by n) ΔP _i : Predicted value of rolling load fluctuation from mill biting during i-point rolling Q _i : Plasticity coefficient of material to be rolled during i-point rolling

Equation (10) is defined by defining the plasticity coefficient Q (Q = −
∂P / ∂h) indicates the rolling load fluctuation amount accompanying the gradual change of the exit taper plate thickness. To accurately predict the rolling load variation by equation (10), the longitudinal direction of the division number n of the rolled material 6 and sufficiently large, the output side tapered thickness changing step size Delta] h _n a so small amount It is desirable. The difference between this equation (10) and the above-mentioned equation ΔP = −Q · Δh _T is that the history of the plasticity coefficient Q of each part in the longitudinal direction of the material 6 to be rolled finally becomes the rolling load fluctuation predicted value ΔP in the former. It is reflected, but not reflected in the latter.

The target roll gap setting unit 15 receives the target taper thickness change Δh _T input from the target taper thickness change amount setting unit 13 and the predicted rolling load fluctuation value given from the rolling load fluctuation predicting unit 14. ΔP , the roll gap S ₀ when the material to be rolled into the rolling mill 1 set from the constant setting device 12, the predicted rolling load P ₀ when the rolling material 1 bites into the rolling mill 1, the mill stiffness coefficient M, and the plate Based on the scale factor K _A , which is the gain of the thickness control system, (7)
The roll gap S _REF (corresponding to the left side of the equation (7)) is calculated according to the equation, and the calculated result is given to the roll gap position control system (16).

Here, it goes without saying that equation (10) is used as ΔP . The roll gap position control system 16 is based on the target roll gap S _REF input from the target roll gap setter 15 and the current rolling position obtained from the rolling position detector 3, that is, the roll gap S, according to the following equation (11). The roll gap change amount ΔS with respect to the rolling device 2 is obtained, and this is used as a control signal as a control signal.
To control the roll gap.

[0025]

(Equation 4)

(Numerical example) In order to compare the conventional control system with the control system according to the present invention, the mill stiffness coefficient 700 ton
/ Mm rolling mill with a taper amount of 15 mm (thickness 17 at the thin end)
mm, a tapered plate having a thick end of 32 mm) was rolled. The scale factor K _A, which is the gain of the thickness control system of the absolute value AGC, is 0.7, and the length of the material to be rolled is 22.
And the plastic coefficient distribution in the longitudinal direction of the material to be rolled was 300 to 1000 ton / mm. As a conventional method
The thickness accuracy when the rolling load fluctuation is predicted using the formula ΔP = −Q · Δh _T and the rolling load fluctuation predicting method (1) of the present invention.
0) was compared with the plate thickness accuracy.

FIG. 3 is a chart showing a comparison of plate thickness accuracy. In the conventional method, as the pressure extension becomes longer and the target outlet taper plate thickness change amount Δh _T becomes larger, the plate thickness deviation becomes larger, and a plate thickness deviation of 0.4 mm or more occurs at the maximum. On the other hand, in the method of the present invention, the thickness deviation is controlled within 0.1 mm over the entire length, and a substantially desired thickness and taper gradient are obtained.

[0028]

As described above, according to the method of the present invention, it is possible to accurately predict the rolling load fluctuation including the effect of the distribution of the plastic coefficient of the material in the longitudinal direction of the material to be rolled, and it is possible to obtain a stable and stable operation. Thus, a tapered plate having a desired tapered gradient can be manufactured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a target taper plate thickness and a target value of a delivery side plate thickness of each portion in a longitudinal direction of a material to be rolled.

FIG. 3 is a table showing comparative test results between the method of the present invention and a conventional method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rolling mill 2 rolling device 3 rolling position detector 4 rolling load detector 5 pulse generator 6 rolled material 11 target taper amount setting device 12 constant setting device 13 target taper plate thickness change amount setting device 14 rolling load fluctuation prediction device 15 Target roll gap setting device 16 Roll gap position control system

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-130205 (JP, A) JP-A-58-196112 (JP, A) JP-A-55-61311 (JP, A) 9983 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 37/24

Claims (1)

(57) [Claims] 1. A relationship between B Rugyappu the rolling load at the time of flat rolling, and using a control system for performing plate thickness control based on the predicted rolling load, changing the tapered accordance rolling length side thickness target output In the method of controlling the thickness of the tapered plate, which continuously changes the exit thickness in the rolling direction, the rolling load variation is calculated from the longitudinal distribution of the plastic coefficient of the material to be rolled and the target exit thickness, and the mill stiffness factor is calculated. And correcting the roll gap based on a gain of the plate thickness control system.